From a0d46c9aae9d03d79b7f9afec9527df6dd6b7957 Mon Sep 17 00:00:00 2001
From: Markus Ebner <hiwatari.seiji@gmail.com>
Date: Sun, 18 Aug 2019 13:42:18 +0200
Subject: [PATCH 1/2] Refactor Logger and add Settings-UI

- Refactored logger infrastructure, so that sensors have to provide
proper timestamps for the logged data, instead of the Logger generating
a timestamp when it is logged to the file.
- Added a settings UI where active sensors and activities can be
configured
---
 .idea/assetWizardSettings.xml                 |  46 ++
 .idea/caches/build_file_checksums.ser         | Bin 0 -> 534 bytes
 .idea/encodings.xml                           |   4 +
 .idea/gradle.xml                              |   3 +-
 .idea/misc.xml                                |  26 +-
 .idea/modules.xml                             |   2 +-
 .idea/runConfigurations.xml                   |  12 +
 app/build.gradle                              |   9 +-
 app/src/main/AndroidManifest.xml              |   8 +-
 .../indoor/sensorreadout/MainActivity.java    | 401 +++++++++---------
 .../sensorreadout/SettingsActivity.java       |  14 +
 .../sensorreadout/SettingsFragment.java       |  16 +
 .../indoor/sensorreadout/sensors/Gps.java     |   2 +-
 .../indoor/sensorreadout/sensors/GpsNew.java  |   2 +-
 .../sensorreadout/sensors/GroundTruth.java    |   5 +-
 .../indoor/sensorreadout/sensors/Logger.java  | 201 +++++----
 .../sensors/PedestrianActivity.java           |   1 +
 .../sensors/PedestrianActivityButton.java     |  46 +-
 .../sensorreadout/sensors/PhoneSensors.java   |  53 ++-
 .../sensorreadout/sensors/SensorType.java     |   1 +
 .../indoor/sensorreadout/sensors/WiFi.java    |   4 +-
 .../indoor/sensorreadout/sensors/iBeacon.java |   2 +-
 .../sensorreadout/sensors/iBeaconOld.java     |   3 +-
 .../sensorreadout/sensors/mySensor.java       |   4 +-
 app/src/main/res/drawable/ic_mess_around.xml  |   9 +
 app/src/main/res/layout/activity_main.xml     | 200 +--------
 app/src/main/res/layout/activity_settings.xml |  21 +
 .../res/layout/pedestrian_activity_button.xml |  26 ++
 app/src/main/res/values/dimens.xml            |   1 +
 app/src/main/res/values/strings.xml           |  42 ++
 app/src/main/res/values/styles.xml            |   9 +
 app/src/main/res/xml/preferences.xml          |  19 +
 build.gradle                                  |   3 +-
 gradle/wrapper/gradle-wrapper.properties      |   4 +-
 34 files changed, 663 insertions(+), 536 deletions(-)
 create mode 100644 .idea/assetWizardSettings.xml
 create mode 100644 .idea/caches/build_file_checksums.ser
 create mode 100644 .idea/encodings.xml
 create mode 100644 .idea/runConfigurations.xml
 create mode 100644 app/src/main/java/de/fhws/indoor/sensorreadout/SettingsActivity.java
 create mode 100644 app/src/main/java/de/fhws/indoor/sensorreadout/SettingsFragment.java
 create mode 100644 app/src/main/res/drawable/ic_mess_around.xml
 create mode 100644 app/src/main/res/layout/activity_settings.xml
 create mode 100644 app/src/main/res/layout/pedestrian_activity_button.xml
 create mode 100644 app/src/main/res/xml/preferences.xml

diff --git a/.idea/assetWizardSettings.xml b/.idea/assetWizardSettings.xml
new file mode 100644
index 0000000..80f880e
--- /dev/null
+++ b/.idea/assetWizardSettings.xml
@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="WizardSettings">
+    <option name="children">
+      <map>
+        <entry key="vectorWizard">
+          <value>
+            <PersistentState>
+              <option name="children">
+                <map>
+                  <entry key="vectorAssetStep">
+                    <value>
+                      <PersistentState>
+                        <option name="children">
+                          <map>
+                            <entry key="clipartAsset">
+                              <value>
+                                <PersistentState>
+                                  <option name="values">
+                                    <map>
+                                      <entry key="url" value="jar:file:/mnt/data/apps/android-studio/plugins/android/lib/android.jar!/images/material_design_icons/action/ic_3d_rotation_black_24dp.xml" />
+                                    </map>
+                                  </option>
+                                </PersistentState>
+                              </value>
+                            </entry>
+                          </map>
+                        </option>
+                        <option name="values">
+                          <map>
+                            <entry key="outputName" value="ic_mess_around" />
+                            <entry key="sourceFile" value="$USER_HOME$" />
+                          </map>
+                        </option>
+                      </PersistentState>
+                    </value>
+                  </entry>
+                </map>
+              </option>
+            </PersistentState>
+          </value>
+        </entry>
+      </map>
+    </option>
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/caches/build_file_checksums.ser b/.idea/caches/build_file_checksums.ser
new file mode 100644
index 0000000000000000000000000000000000000000..e96d59a23f991ff59bbdd50be9dea49fb847e731
GIT binary patch
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zTj0aMpIeEdv4nx&Co8cmQNOe#Ge_SyvB0{bfPsNAr|Tl~DWJOqL2`N^IX#cW;tZfX
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zMa8KlC7F5Y#ZX_B7BMhIJFWRF{)3Gp<N*@{1IT6uf#v_C4o}S7`cxw-E;vnJRl0;h
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zJV~GsgV_sL$g}Z?{(@C8dkcTQ^eEyx!e7E5kdvRBm;(xL3{y3YoFx)#(oU+sE#h;O
zT<2B7Ac)5ea;~>MIozhkc6Z%<nw<6L5YXtvf&zW)?kHvvX!W(>dbh(NMJe;{+_Mz`
DX#=;E

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HcmV?d00001

diff --git a/.idea/encodings.xml b/.idea/encodings.xml
new file mode 100644
index 0000000..15a15b2
--- /dev/null
+++ b/.idea/encodings.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding" addBOMForNewFiles="with NO BOM" />
+</project>
\ No newline at end of file
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index cfe4315..7ac24c7 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -3,9 +3,8 @@
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
-        <option name="distributionType" value="LOCAL" />
+        <option name="distributionType" value="DEFAULT_WRAPPED" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleHome" value="$APPLICATION_HOME_DIR$/gradle/gradle-2.10" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />
diff --git a/.idea/misc.xml b/.idea/misc.xml
index ba7052b..7bfef59 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,30 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="NullableNotNullManager">
-    <option name="myDefaultNullable" value="android.support.annotation.Nullable" />
-    <option name="myDefaultNotNull" value="android.support.annotation.NonNull" />
-    <option name="myNullables">
-      <value>
-        <list size="4">
-          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.Nullable" />
-          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nullable" />
-          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.Nullable" />
-          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.Nullable" />
-        </list>
-      </value>
-    </option>
-    <option name="myNotNulls">
-      <value>
-        <list size="4">
-          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.NotNull" />
-          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nonnull" />
-          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.NonNull" />
-          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.NonNull" />
-        </list>
-      </value>
-    </option>
-  </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="1.8" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
   <component name="ProjectType">
diff --git a/.idea/modules.xml b/.idea/modules.xml
index 9a8c334..36c117d 100644
--- a/.idea/modules.xml
+++ b/.idea/modules.xml
@@ -2,8 +2,8 @@
 <project version="4">
   <component name="ProjectModuleManager">
     <modules>
-      <module fileurl="file://$PROJECT_DIR$/SensorReadout.iml" filepath="$PROJECT_DIR$/SensorReadout.iml" />
       <module fileurl="file://$PROJECT_DIR$/app/app.iml" filepath="$PROJECT_DIR$/app/app.iml" />
+      <module fileurl="file://$PROJECT_DIR$/sensorreadout.iml" filepath="$PROJECT_DIR$/sensorreadout.iml" />
     </modules>
   </component>
 </project>
\ No newline at end of file
diff --git a/.idea/runConfigurations.xml b/.idea/runConfigurations.xml
new file mode 100644
index 0000000..7f68460
--- /dev/null
+++ b/.idea/runConfigurations.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="RunConfigurationProducerService">
+    <option name="ignoredProducers">
+      <set>
+        <option value="org.jetbrains.plugins.gradle.execution.test.runner.AllInPackageGradleConfigurationProducer" />
+        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestClassGradleConfigurationProducer" />
+        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestMethodGradleConfigurationProducer" />
+      </set>
+    </option>
+  </component>
+</project>
\ No newline at end of file
diff --git a/app/build.gradle b/app/build.gradle
index 983ed45..b2cc588 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -2,7 +2,7 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 23
-    buildToolsVersion '26.0.2'
+    buildToolsVersion '26.0.3'
 
     defaultConfig {
         applicationId "de.fhws.indoor.sensorreadout"
@@ -20,10 +20,13 @@ android {
 }
 
 dependencies {
+    implementation 'com.android.support:design:23.4.0'
     compile fileTree(include: ['*.jar'], dir: 'libs')
     testCompile 'junit:junit:4.12'
-    compile 'com.android.support:appcompat-v7:23.4.0'
-    compile 'com.google.android.gms:play-services:10.2.0'
+    implementation 'com.android.support:appcompat-v7:23.4.0'
+    implementation 'com.google.android.gms:play-services:10.2.0'
+    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
+    implementation 'org.apmem.tools:layouts:1.10@aar'
     //compile 'com.google.android.support:wearable:1.3.0'
     //compile 'com.google.android.gms:play-services-wearable:8.4.0'
     //provided 'com.google.android.wearable:wearable:1.0.0'
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 6c5724c..de7f3dc 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -1,10 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="de.fhws.indoor.sensorreadout">
-    >
-
     <!-- <uses-feature android:name="android.hardware.type.watch" /> -->
-
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
     <uses-permission android:name="android.permission.BLUETOOTH" />
@@ -13,8 +10,7 @@
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
     <uses-permission android:name="android.permission.BODY_SENSORS" />
-    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
-    <!-- Needed only if your app targets Android 5.0 (API level 21) or higher. -->
+    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> <!-- Needed only if your app targets Android 5.0 (API level 21) or higher. -->
     <uses-feature android:name="android.hardware.location.gps" />
 
     <uses-permission-sdk-23 android:name="android.permission.ACCESS_FINE_LOCATION" />
@@ -24,6 +20,8 @@
         android:icon="@drawable/icon"
         android:label="@string/app_name"
         android:theme="@style/AppTheme">
+        <activity android:name=".SettingsActivity"></activity>
+
         <uses-library
             android:name="com.google.android.wearable"
             android:required="false" />
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java b/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java
index f4f22db..03e182f 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java
@@ -4,30 +4,34 @@ import android.Manifest;
 import android.app.Activity;
 import android.app.ActivityManager;
 import android.content.Context;
+import android.content.Intent;
+import android.content.SharedPreferences;
 import android.content.res.Configuration;
-import android.graphics.Color;
 import android.media.MediaPlayer;
 import android.os.Build;
 import android.os.Bundle;
+import android.os.SystemClock;
+import android.preference.PreferenceManager;
 import android.support.v4.app.ActivityCompat;
-import android.support.v4.content.pm.ActivityInfoCompat;
 //import android.support.wearable.activity.WearableActivity;
 import android.util.Log;
 import android.view.View;
 import android.widget.ArrayAdapter;
 import android.widget.Button;
-import android.widget.LinearLayout;
 import android.widget.Spinner;
+import android.widget.TableLayout;
+import android.widget.TableRow;
 import android.widget.TextView;
 import android.widget.Toast;
 import android.view.ViewGroup.LayoutParams;
 
-import com.google.android.gms.vision.text.Line;
-
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
-import de.fhws.indoor.sensorreadout.sensors.Gps;
 import de.fhws.indoor.sensorreadout.sensors.GpsNew;
 import de.fhws.indoor.sensorreadout.sensors.GroundTruth;
 import de.fhws.indoor.sensorreadout.sensors.Logger;
@@ -43,19 +47,20 @@ import de.fhws.indoor.sensorreadout.sensors.SensorType;
 
 public class MainActivity extends Activity {
 
+    MediaPlayer mpStart;
+    MediaPlayer mpStop;
+    MediaPlayer mpGround;
+    MediaPlayer mpFailure;
+
     private final ArrayList<mySensor> sensors = new ArrayList<mySensor>();
     private final Logger logger = new Logger(this);
     private Button btnStart;
     private Button btnStop;
     private Button btnGround;
-    private PedestrianActivityButton btnWalk;
-    private PedestrianActivityButton btnStand;
-    private PedestrianActivityButton btnStairsUp;
-    private PedestrianActivityButton btnStairsDown;
-    private PedestrianActivityButton btnElevatorUp;
-    private PedestrianActivityButton btnElevatorDown;
-    private PedestrianActivity currentPedestrianActivity;
-    private PedestrianActivity pastPedestrianActivity;
+    private Button btnSettings;
+    private TableLayout activityButtonContainer;
+    private HashMap<PedestrianActivity, PedestrianActivityButton> activityButtons = new HashMap<>();
+    private PedestrianActivity currentPedestrianActivity = PedestrianActivity.STANDING;
 
     private int groundTruthCounter = 0;
     private boolean isInitialized = false;
@@ -70,10 +75,18 @@ public class MainActivity extends Activity {
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+        // This static call will reset default values for preferences only on the first ever read
+        PreferenceManager.setDefaultValues(getBaseContext(), R.xml.preferences, false);
 
         // context access
         MainActivity.context = getApplicationContext();
 
+        // setup sound-effects
+        mpStart = MediaPlayer.create(this, R.raw.go);
+        mpStop = MediaPlayer.create(this, R.raw.go);
+        mpGround = MediaPlayer.create(this, R.raw.go);
+        mpFailure = MediaPlayer.create(this, R.raw.error);
+
         //init Path spinner
         final Spinner pathSpinner = (Spinner) findViewById(R.id.pathspinner);
         List<String> pathList = new ArrayList<String>();
@@ -100,31 +113,15 @@ public class MainActivity extends Activity {
         btnStart = (Button) findViewById(R.id.btnStart);
         btnStop = (Button) findViewById(R.id.btnStop);
         btnGround = (Button) findViewById(R.id.btnGround);
-
-        //get activity Buttons
-        btnWalk = new PedestrianActivityButton((LinearLayout) findViewById(R.id.btnWalk), PedestrianActivity.WALK);
-        btnStand = new PedestrianActivityButton((LinearLayout) findViewById(R.id.btnStanding), PedestrianActivity.STANDING);
-        btnStairsUp = new PedestrianActivityButton((LinearLayout) findViewById(R.id.btnStairsUp), PedestrianActivity.STAIRS_UP);
-        btnStairsDown = new PedestrianActivityButton((LinearLayout) findViewById(R.id.btnStairsDown), PedestrianActivity.STAIRS_DOWN);
-        btnElevatorUp = new PedestrianActivityButton((LinearLayout) findViewById(R.id.btnElevatorUp), PedestrianActivity.ELEVATOR_UP);
-        btnElevatorDown = new PedestrianActivityButton((LinearLayout) findViewById(R.id.btnElevatorDown), PedestrianActivity.ELEVATOR_DOWN);
-
-        //set current activity
-        btnStand.toggleActivity(); //first activity is standing!
-        currentPedestrianActivity = PedestrianActivity.STANDING;
-
-        //Click Sound
-        final MediaPlayer mpStart = MediaPlayer.create(this, R.raw.go);
-        final MediaPlayer mpStop = MediaPlayer.create(this, R.raw.go);
-        final MediaPlayer mpGround = MediaPlayer.create(this, R.raw.go);
-        final MediaPlayer mpFailure = MediaPlayer.create(this, R.raw.error);
+        btnSettings = (Button) findViewById(R.id.btnSettings);
+        activityButtonContainer = (TableLayout) findViewById(R.id.pedestrianActivityButtonContainer);
 
         // log GroundTruth ButtonClicks using sensor number 99
         final GroundTruth grndTruth = new GroundTruth(this);
         sensors.add(grndTruth);
         grndTruth.setListener(new mySensor.SensorListener() {
-            @Override public void onData(final String csv) { return; }
-            @Override public void onData(SensorType id, final String csv) {add(id, csv); }
+            @Override public void onData(final long timestamp, final String csv) { return; }
+            @Override public void onData(SensorType id, final long timestamp, final String csv) {add(id, csv, timestamp); }
         });
 
 
@@ -144,7 +141,7 @@ public class MainActivity extends Activity {
                     grndTruth.writeGroundTruth(groundTruthCounter);
 
                     //Write first activity
-                    add(SensorType.PEDESTRIAN_ACTIVITY, PedestrianActivity.STANDING.toString() + ";" + PedestrianActivity.STANDING.ordinal());
+                    add(SensorType.PEDESTRIAN_ACTIVITY, PedestrianActivity.STANDING.toString() + ";" + PedestrianActivity.STANDING.ordinal(), Logger.BEGINNING_TS);
 
                     //Disable the spinners
                     groundSpinner.setEnabled(false);
@@ -153,7 +150,6 @@ public class MainActivity extends Activity {
                 else{
                     mpFailure.start();
                 }
-
             }
         });
 
@@ -174,7 +170,7 @@ public class MainActivity extends Activity {
                     pathSpinner.setEnabled(true);
 
                     //reset activity buttons
-                    setActivityBtn(PedestrianActivity.STANDING);
+                    setActivityBtn(PedestrianActivity.STANDING, false);
                 }
                 else{
                     mpFailure.start();
@@ -201,166 +197,28 @@ public class MainActivity extends Activity {
             }
         });
 
-
-        btnWalk.getLayout().setOnClickListener(new View.OnClickListener() {
-            @Override public void onClick(View v) {
-                if(isInitialized) {
-                    setActivityBtn(PedestrianActivity.WALK);
-                }
-                else{
+        btnSettings.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                if(!isInitialized) { // Only allow when not currently running
+                    startActivity(new Intent(context, SettingsActivity.class));
+                } else {
                     mpFailure.start();
                 }
             }
         });
-
-        btnStand.getLayout().setOnClickListener(new View.OnClickListener() {
-            @Override public void onClick(View v) {
-                if(isInitialized) {
-                    setActivityBtn(PedestrianActivity.STANDING);
-                }
-                else{
-                    mpFailure.start();
-                }
-            }
-        });
-
-        btnStairsUp.getLayout().setOnClickListener(new View.OnClickListener() {
-            @Override public void onClick(View v) {
-                if(isInitialized) {
-                    setActivityBtn(PedestrianActivity.STAIRS_UP);
-                }
-                else{
-                    mpFailure.start();
-                }
-            }
-        });
-
-        btnStairsDown.getLayout().setOnClickListener(new View.OnClickListener() {
-            @Override public void onClick(View v) {
-                if(isInitialized) {
-                    setActivityBtn(PedestrianActivity.STAIRS_DOWN);
-                }
-                else{
-                    mpFailure.start();
-                }
-            }
-        });
-
-        btnElevatorUp.getLayout().setOnClickListener(new View.OnClickListener() {
-            @Override public void onClick(View v) {
-                if(isInitialized) {
-                    setActivityBtn(PedestrianActivity.ELEVATOR_UP);
-                }
-                else{
-                    mpFailure.start();
-                }
-            }
-        });
-
-        btnElevatorDown.getLayout().setOnClickListener(new View.OnClickListener() {
-            @Override public void onClick(View v) {
-                if(isInitialized) {
-                    setActivityBtn(PedestrianActivity.ELEVATOR_DOWN);
-                }
-                else{
-                    mpFailure.start();
-                }
-            }
-        });
-
-        //all Sensors
-        final PhoneSensors phoneSensors = new PhoneSensors(this);
-        sensors.add(phoneSensors);
-        phoneSensors.setListener(new mySensor.SensorListener(){
-            @Override public void onData(final String csv) { return; }
-            @Override public void onData(final SensorType id, final String csv) {add(id, csv); }
-        });
-
-        // logo wifi using sensor number 8
-        final WiFi wifi = new WiFi(this);
-        sensors.add(wifi);
-        wifi.setListener(new mySensor.SensorListener() {
-            @Override public void onData(final String csv) { add(SensorType.WIFI, csv); }
-            @Override public void onData(final SensorType id, final String csv) {return; }
-        });
-
-        //log gps using sensor number 16
-        final GpsNew gps = new GpsNew(this);
-        sensors.add(gps);
-        gps.setListener(new mySensor.SensorListener(){
-            @Override public void onData(final String csv) { add(SensorType.GPS, csv); }
-            @Override public void onData(final SensorType id, final String csv) {return; }
-        });
-
-        // log iBeacons using sensor number 9
-        final mySensor beacon;
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-            beacon = new iBeacon(this);
-        } else{
-            beacon = new iBeaconOld(this);
-        }
-
-        sensors.add(beacon);
-        beacon.setListener(new mySensor.SensorListener() {
-            @Override public void onData(final String csv) { add(SensorType.IBEACON, csv); }
-            @Override public void onData(final SensorType id, final String csv) {return; }
-        });
-
-
-        // bluetooth permission
-        if(ActivityCompat.shouldShowRequestPermissionRationale(this,
-                Manifest.permission.ACCESS_FINE_LOCATION)) {
-        } else {
-            ActivityCompat.requestPermissions(this,
-                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
-                    MY_PERMISSIONS_REQUEST_READ_BT);
-        }
-
-        // heartbeat permission
-/*        if(ActivityCompat.shouldShowRequestPermissionRationale(this,
-                Manifest.permission.BODY_SENSORS)) {
-        } else {
-            ActivityCompat.requestPermissions(this,
-                    new String[]{Manifest.permission.BODY_SENSORS},
-                    MY_PERMISSIONS_REQUEST_READ_HEART);
-        }*/
-
     }
 
 
-    private void setActivityBtn(PedestrianActivity act){
-
-        // set and write new activity
-        if(currentPedestrianActivity != act){
-
-            // toggle past and current activity
-            PedestrianActivity[] tmpActArray = new PedestrianActivity[] {currentPedestrianActivity, act};
-
-            for(PedestrianActivity a : tmpActArray){
-                switch (a) {
-                    case WALK: btnWalk.toggleActivity();
-                        break;
-                    case STANDING: btnStand.toggleActivity();
-                        break;
-                    case STAIRS_UP:  btnStairsUp.toggleActivity();
-                        break;
-                    case STAIRS_DOWN:  btnStairsDown.toggleActivity();
-                        break;
-                    case ELEVATOR_UP:  btnElevatorUp.toggleActivity();
-                        break;
-                    case ELEVATOR_DOWN:  btnElevatorDown.toggleActivity();
-                        break;
-                    default:
-                        break;
-                }
-            }
-
-            currentPedestrianActivity = act;
-            add(SensorType.PEDESTRIAN_ACTIVITY, act.toString() + ";" + act.ordinal());
-        } else {
-            //do nothin
+    private void setActivityBtn(PedestrianActivity newActivity, boolean logChange){
+        if(activityButtons.containsKey(currentPedestrianActivity)) {
+            activityButtons.get(currentPedestrianActivity).setActivity(false);
+        }
+        currentPedestrianActivity = newActivity;
+        activityButtons.get(newActivity).setActivity(true);
+        if(logChange) {
+            add(SensorType.PEDESTRIAN_ACTIVITY, newActivity.toString() + ";" + newActivity.ordinal());
         }
-
     }
 
     private void start() {
@@ -386,8 +244,11 @@ public class MainActivity extends Activity {
     private int loadCounterGPS = 0;
     private int loadCounterAny = 0;
     private void add(final SensorType id, final String csv) {
+        add(id, csv, SystemClock.elapsedRealtimeNanos());
+    }
+    private void add(final SensorType id, final String csv, final long timestamp) {
 
-        logger.addCSV(id, csv);
+        logger.addCSV(id, timestamp, csv);
 
         runOnUiThread(new Runnable() {
             @Override public void run() {
@@ -405,8 +266,9 @@ public class MainActivity extends Activity {
                 // dump buffer stats every x entries
                 if (++loadCounterAny % 250 == 0) {
                     final TextView txt = (TextView) findViewById(R.id.txtBuffer);
-                    final int kbPerMin = (int) (logger.getTotalSize() / 1024 * 1000 * 60 / (System.currentTimeMillis() - logger.getStartTS()));
-                    txt.setText( (logger.getCurrentSize() / 1024) + "k, " + logger.getNumEntries() + ", " + kbPerMin + "k/m");
+                    final float elapsedMinutes = (timestamp - logger.getStartTS()) / 1000.0f / 1000.0f / 1000.0f / 60.0f;
+                    final int kBPerMin = (int) (logger.getTotalSize() / 1024.0f / elapsedMinutes);
+                    txt.setText( (logger.getCurrentBufferSize() / 1024) + "k, " + logger.getNumEntries() + ", " + kBPerMin + "kB/m");
                 }
 
             }
@@ -420,11 +282,20 @@ public class MainActivity extends Activity {
         super.onPause();
     }
 
+    protected void onStart() {
+        super.onStart();
+        if(!isInitialized) {
+            // Do not apply new settings when recording is currently running, since we can't have come
+            // from the SettingsActivity, then.
+            setupActivityButtons();
+            setupSensors();
+        }
+    }
+
     /** resume activity */
     protected void onResume() {
         super.onResume();
 
-
         //print memory info
         ActivityManager.MemoryInfo mi = new ActivityManager.MemoryInfo();
         ActivityManager activityManager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
@@ -459,4 +330,148 @@ public class MainActivity extends Activity {
         return MainActivity.context;
     }
 
+
+
+
+
+
+    protected void setupActivityButtons() {
+        // cleanup before recreation
+        for(int i = 0; i < activityButtonContainer.getChildCount(); ++i) {
+            TableRow buttonRow = (TableRow)activityButtonContainer.getChildAt(i);
+            buttonRow.removeAllViews();
+        }
+        activityButtonContainer.removeAllViews();
+        activityButtons.clear();
+
+        // setup activity buttons
+        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
+        Set<String> activeActivities = preferences.getStringSet("prefActiveActions", new HashSet<String>());
+
+        activityButtons.put(PedestrianActivity.STANDING, new PedestrianActivityButton(this, PedestrianActivity.STANDING, R.drawable.ic_standing));
+        if(activeActivities.contains("WALK")) {
+            activityButtons.put(PedestrianActivity.WALK, new PedestrianActivityButton(this, PedestrianActivity.WALK, R.drawable.ic_walk));
+        }
+        if(activeActivities.contains("ELEVATOR")) {
+            activityButtons.put(PedestrianActivity.ELEVATOR_UP, new PedestrianActivityButton(this, PedestrianActivity.ELEVATOR_UP, R.drawable.ic_elevator_up));
+            activityButtons.put(PedestrianActivity.ELEVATOR_DOWN, new PedestrianActivityButton(this, PedestrianActivity.ELEVATOR_DOWN, R.drawable.ic_elevator_down));
+        }
+        if(activeActivities.contains("STAIRS")) {
+            activityButtons.put(PedestrianActivity.STAIRS_UP, new PedestrianActivityButton(this, PedestrianActivity.STAIRS_UP, R.drawable.ic_stairs_up));
+            activityButtons.put(PedestrianActivity.STAIRS_DOWN, new PedestrianActivityButton(this, PedestrianActivity.STAIRS_DOWN, R.drawable.ic_stairs_down));
+        }
+        if(activeActivities.contains("MESS_AROUND")) {
+            activityButtons.put(PedestrianActivity.MESS_AROUND, new PedestrianActivityButton(this, PedestrianActivity.MESS_AROUND, R.drawable.ic_mess_around));
+        }
+        int activityButtonColumns = 1;
+        if(activityButtons.size() > 6) { activityButtonColumns = 4; }
+        else if(activityButtons.size() > 4) { activityButtonColumns = 3; }
+        else if(activityButtons.size() > 2) { activityButtonColumns = 2; }
+
+        TableLayout.LayoutParams rowLayout = new TableLayout.LayoutParams();
+        rowLayout.width = LayoutParams.MATCH_PARENT;
+        rowLayout.height = LayoutParams.WRAP_CONTENT;
+        rowLayout.weight = 1.0f;
+        TableRow.LayoutParams columnLayout = new TableRow.LayoutParams();
+        columnLayout.height = LayoutParams.MATCH_PARENT;
+        columnLayout.width = 1; // set minWidth to 1, because this will be stretched, and the images adjust in size
+        columnLayout.weight = 1.0f;
+        PedestrianActivity[] activeActiviesArray = activityButtons.keySet().toArray(new PedestrianActivity[activityButtons.size()]);
+        Arrays.sort(activeActiviesArray);
+        TableRow currentButtonRow = null;
+        for(int i = 0; i < activeActiviesArray.length; ++i) {
+            final PedestrianActivityButton button = activityButtons.get(activeActiviesArray[i]);
+            if(i % activityButtonColumns == 0) {
+                currentButtonRow = new TableRow(this);
+                currentButtonRow.setWeightSum(1.0f * activityButtonColumns);
+                activityButtonContainer.addView(currentButtonRow, rowLayout);
+            }
+            currentButtonRow.addView(button, columnLayout);
+            button.setOnClickListener(new View.OnClickListener() {
+                @Override
+                public void onClick(View v) {
+                    if(isInitialized) {
+                        setActivityBtn(button.getPedestrianActivity(), true);
+                    }
+                    else{
+                        mpFailure.start();
+                    }
+                }
+            });
+        }
+
+        //set current activity
+        setActivityBtn(PedestrianActivity.STANDING, false);
+    }
+
+    protected void setupSensors() {
+        //cleanup first
+        sensors.clear();
+
+        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
+        Set<String> activeSensors = preferences.getStringSet("prefActiveSensors", new HashSet<String>());
+
+        if(activeSensors.contains("PHONE")) {
+            // heartbeat permission
+            if(ActivityCompat.shouldShowRequestPermissionRationale(this,
+                    Manifest.permission.BODY_SENSORS)) {
+            } else {
+                ActivityCompat.requestPermissions(this,
+                        new String[]{Manifest.permission.BODY_SENSORS},
+                        MY_PERMISSIONS_REQUEST_READ_HEART);
+            }
+
+            //all Phone-Sensors (Accel, Gyro, Magnet, ...)
+            final PhoneSensors phoneSensors = new PhoneSensors(this);
+            sensors.add(phoneSensors);
+            phoneSensors.setListener(new mySensor.SensorListener(){
+                @Override public void onData(final long timestamp, final String csv) { return; }
+                @Override public void onData(final SensorType id, final long timestamp, final String csv) {add(id, csv, timestamp); }
+            });
+        }
+        if(activeSensors.contains("GPS")) {
+            //log gps using sensor number 16
+            final GpsNew gps = new GpsNew(this);
+            sensors.add(gps);
+            gps.setListener(new mySensor.SensorListener(){
+                @Override public void onData(final long timestamp, final String csv) { add(SensorType.GPS, csv, timestamp); }
+                @Override public void onData(final SensorType id, final long timestamp, final String csv) {return; }
+            });
+        }
+        if(activeSensors.contains("WIFI")) {
+            // logo wifi using sensor number 8
+            final WiFi wifi = new WiFi(this);
+            sensors.add(wifi);
+            wifi.setListener(new mySensor.SensorListener() {
+                @Override public void onData(final long timestamp, final String csv) { add(SensorType.WIFI, csv, timestamp); }
+                @Override public void onData(final SensorType id, final long timestamp, final String csv) {return; }
+            });
+        }
+        if(activeSensors.contains("BLUETOOTH")) {
+            // bluetooth permission
+            if(ActivityCompat.shouldShowRequestPermissionRationale(this,
+                    Manifest.permission.ACCESS_FINE_LOCATION)) {
+            } else {
+                ActivityCompat.requestPermissions(this,
+                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
+                        MY_PERMISSIONS_REQUEST_READ_BT);
+            }
+
+            // log iBeacons using sensor number 9
+            final mySensor beacon;
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+                beacon = new iBeacon(this);
+            } else{
+                beacon = new iBeaconOld(this);
+            }
+
+            sensors.add(beacon);
+            beacon.setListener(new mySensor.SensorListener() {
+                @Override public void onData(final long timestamp, final String csv) { add(SensorType.IBEACON, csv, timestamp); }
+                @Override public void onData(final SensorType id, final long timestamp, final String csv) {return; }
+            });
+        }
+    }
+
+
 }
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/SettingsActivity.java b/app/src/main/java/de/fhws/indoor/sensorreadout/SettingsActivity.java
new file mode 100644
index 0000000..4bcc46f
--- /dev/null
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/SettingsActivity.java
@@ -0,0 +1,14 @@
+package de.fhws.indoor.sensorreadout;
+
+import android.preference.PreferenceManager;
+import android.support.v7.app.AppCompatActivity;
+import android.os.Bundle;
+
+public class SettingsActivity extends AppCompatActivity {
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        getFragmentManager().beginTransaction().replace(android.R.id.content, new SettingsFragment()).commit();
+    }
+}
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/SettingsFragment.java b/app/src/main/java/de/fhws/indoor/sensorreadout/SettingsFragment.java
new file mode 100644
index 0000000..18f185c
--- /dev/null
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/SettingsFragment.java
@@ -0,0 +1,16 @@
+package de.fhws.indoor.sensorreadout;
+
+import android.os.Bundle;
+import android.preference.PreferenceFragment;
+import android.support.annotation.Nullable;
+
+public class SettingsFragment extends PreferenceFragment {
+
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        addPreferencesFromResource(R.xml.preferences);
+    }
+
+}
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Gps.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Gps.java
index eec513f..63b71d7 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Gps.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Gps.java
@@ -85,7 +85,7 @@ public class Gps extends mySensor implements LocationListener {
 
         // inform listeners
         if (listener != null){
-            listener.onData(SensorType.GRAVITY,
+            listener.onData(SensorType.GRAVITY, location.getElapsedRealtimeNanos(), //TODO: Is this correct? SystemClock.elapsedRealtimeNanos() otherwise..
                     Double.toString(location.getLatitude()) + ";" +
                     Double.toString(location.getLongitude()) + ";" +
                     Double.toString(location.getAltitude()) + ";" +
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GpsNew.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GpsNew.java
index f969c03..bf085de 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GpsNew.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GpsNew.java
@@ -169,7 +169,7 @@ public class GpsNew extends mySensor implements ConnectionCallbacks, OnConnectio
 
         // inform listeners
         if (listener != null){
-            listener.onData(SensorType.GRAVITY,
+            listener.onData(SensorType.GRAVITY, location.getElapsedRealtimeNanos(), //TODO: Is this correct? SystemClock.elapsedRealtimeNanos() otherwise..
                     Double.toString(location.getLatitude()) + ";" +
                             Double.toString(location.getLongitude()) + ";" +
                             Double.toString(location.getAltitude()) + ";" +
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GroundTruth.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GroundTruth.java
index e1e7143..97c1ef8 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GroundTruth.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/GroundTruth.java
@@ -1,6 +1,7 @@
 package de.fhws.indoor.sensorreadout.sensors;
 
 import android.app.Activity;
+import android.os.SystemClock;
 
 /**
  * Created by Toni on 02.06.2015.
@@ -12,14 +13,14 @@ public class GroundTruth extends mySensor {
     }
 
     public void writeGroundTruth(final int groundTruthCounter){
-        if (listener != null){listener.onData(SensorType.GROUND_TRUTH,
+        if (listener != null){listener.onData(SensorType.GROUND_TRUTH, SystemClock.elapsedRealtimeNanos(),
                 Integer.toString(groundTruthCounter)
         );}
     }
 
     public void writeInitData(int pathID, int numGroundTruthPoints){
 
-        if (listener != null){listener.onData(SensorType.GROUND_TRUTH_PATH,
+        if (listener != null){listener.onData(SensorType.GROUND_TRUTH_PATH, SystemClock.elapsedRealtimeNanos(),
                 Integer.toString(pathID) + ";" +
                 Integer.toString(numGroundTruthPoints)
         );}
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java
index 4b363ae..b73da7a 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java
@@ -2,27 +2,41 @@ package de.fhws.indoor.sensorreadout.sensors;
 
 import android.content.Context;
 import android.os.AsyncTask;
+import android.os.SystemClock;
+import android.support.annotation.NonNull;
 import android.util.Log;
 
 import java.io.File;
 import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.PriorityQueue;
+import java.util.concurrent.Semaphore;
 
 /**
  * log sensor data to file
  * Created by Frank on 25.03.2015.
+ * Re-Written by Markus on 20.06.2019.
  */
 public final class Logger {
 
-	private static final int FLUSH_LIMIT = 2*1024*1024;
+	public static final long BEGINNING_TS = -1;
 
-	private StringBuilder sb = new StringBuilder();
+	private static final int CACHED_ENTRIES = 1000;
+	private static final int FLUSH_BATCH_SIZE = 100;
+
+	private StringBuilder stringBuilder = new StringBuilder();
 	private File file;
 	private FileOutputStream fos;
 	private Context context;
 
 	private int entries = 0;
-	private int sizeCurrent = 0;
 	private int sizeTotal = 0;
+	private int currentSize = 0;
+
+	private volatile boolean addingStopped = false; // Just to be sure
+	private PriorityQueue<LogEntry> reorderBuffer = new PriorityQueue<>(2 * CACHED_ENTRIES + FLUSH_BATCH_SIZE);
+	private Semaphore flushSemaphore = new Semaphore(0);
+	private WriteBackWorker writeBackWorker;
 
 	/** timestamp of logging start. all entries are relative to this one */
 	private long startTS = 0;
@@ -35,13 +49,15 @@ public final class Logger {
 	public final void start() {
 
 		// start empty
-		sb.setLength(0);
+		stringBuilder.setLength(0);
 		entries = 0;
 		sizeTotal = 0;
-		sizeCurrent = 0;
+		addingStopped = false;
+		flushSemaphore.drainPermits();
+		writeBackWorker = new WriteBackWorker();
 
 		// starting timestamp
-		startTS = System.currentTimeMillis();
+		startTS = SystemClock.elapsedRealtimeNanos();
 
 		// open the output-file immeditaly (to get permission errors)
 		// but do NOT yet write anything to the file
@@ -54,88 +70,68 @@ public final class Logger {
 		} catch (final Exception e) {
 			throw new MyException("error while opening log-file", e);
 		}
-
+		writeBackWorker.start();
 	}
 
 	/** stop logging and flush RAM-data to the flash-chip */
 	public final void stop() {
-		synchronized (this) {
-			flush(true);
-			close();
+	    debug(true);
+		synchronized (reorderBuffer) {
+			addingStopped = true;
+			// Unblock WriteBackThread for all remaining log-lines (+1)
+			// some elements in reorderBuffer could already have been released for flushing -> this might release more than necessary.
+			flushSemaphore.release(reorderBuffer.size() + 1);
 		}
+		// wait for flushing to succeed
+		try {
+			writeBackWorker.join();
+		} catch (InterruptedException e) {
+			e.printStackTrace();
+		}
+		debug(true);
+		close();
 	}
 
 	public File getFile() {
 		return file;
 	}
 
-	public int getCurrentSize() {return sizeCurrent;}
+	public int getCurrentBufferSize() {return currentSize;}
 	public int getTotalSize() {return sizeTotal;}
 
 	public int getNumEntries() {return entries;}
 
 	/** add a new CSV entry for the given sensor number to the internal buffer */
-	public final void addCSV(final SensorType sensorNr, final String csv) {
-		synchronized (this) {
-			final long relTS = System.currentTimeMillis() - startTS;
-			sb.append(relTS);	// relative timestamp (uses less space)
-			sb.append(';');
-			sb.append(sensorNr.id());
-			sb.append(';');
-			sb.append(csv);
-			sb.append('\n');
-			++entries;
-			sizeTotal += csv.length() + 10; // approx!
-			sizeCurrent = sb.length();
-			if (sb.length() > FLUSH_LIMIT) {flush(false);}
+	public final void addCSV(final SensorType sensorNr, final long timestamp, final String csv) {
+		final long relTS = (timestamp == BEGINNING_TS) ? 0 : (timestamp - startTS);
+		if(relTS >= 0) { // drop pre startTS logs (at the beginning, sensors sometimes deliver old values)
+			synchronized (reorderBuffer) {
+				if(addingStopped) {
+					// addCSV was called after calling stop();
+					return;
+				}
+
+				stringBuilder.append(relTS);	// relative timestamp (uses less space)
+				stringBuilder.append(';');
+				stringBuilder.append(sensorNr.id());
+				stringBuilder.append(';');
+				stringBuilder.append(csv);
+				stringBuilder.append('\n');
+				++entries;
+				LogEntry logEntry = new LogEntry(relTS, stringBuilder.toString());
+				sizeTotal += logEntry.csv.length();
+				currentSize += logEntry.csv.length();
+				stringBuilder.setLength(0);
+
+				// commit to reorder-buffer and start flush (if necessary)
+				reorderBuffer.add(logEntry);
+				if(flushSemaphore.availablePermits() == 0 && reorderBuffer.size() > (CACHED_ENTRIES + FLUSH_BATCH_SIZE)) {
+					// Unblock WriteBackThread and allow it to flush FLUSH_BATCH_SIZE csv-lines.
+					flushSemaphore.release(reorderBuffer.size() - CACHED_ENTRIES);
+				}
+			}
 		}
-
-		debug();
-	}
-
-
-
-	/** helper method for exception-less writing. DO NOT CALL DIRECTLY! */
-	private final void _write(final byte[] data) {
-		try {
-			fos.write(data);
-			Log.d("logger", "flushed " + data.length + " bytes to disk");
-		} catch (final Exception e) {
-			throw new RuntimeException("error while writing log-file", e);
-		}
-	}
-
-	/** helper-class for background writing */
-	class FlushAsync extends AsyncTask<byte[], Integer, Integer> {
-		@Override
-		protected final Integer doInBackground(byte[][] data) {
-			_write(data[0]);
-			return null;
-		}
-	};
-
-	/** flush current buffer-contents to disk */
-	private final void flush(boolean sync) {
-
-		// fetch current buffer contents to write and hereafter empty the buffer
-		// this action MUST be atomic, just like the add-method
-		byte[] data = null;
-		synchronized (this) {
-			data = sb.toString().getBytes();		// fetch data to write
-			sb.setLength(0);						// reset the buffer
-			sizeCurrent = 0;
-		}
-
-		// write
-		if (sync) {
-			// write to disk using the current thread
-			_write(data);
-		} else {
-			// write to disk using a background-thread
-			new FlushAsync().execute(new byte[][] {data});
-		}
-
-
+        debug(false);
 	}
 
 	private final void close() {
@@ -151,10 +147,67 @@ public final class Logger {
 	}
 
 	int cnt = 0;
-	private final void debug() {
-		if (++cnt % 1000 == 0) {
-			Log.d("buffer", "size: " + sizeCurrent);
+	private final void debug(boolean force) {
+		if (++cnt % 1000 == 0 || force) {
+			Log.d("buffer", "size: " + reorderBuffer.size() + " lines");
 		}
 	}
 
+
+
+	private static class LogEntry implements Comparable<LogEntry> {
+		public long timestamp;
+		public String csv;
+
+		public LogEntry(long timestamp, String csv) {
+			this.timestamp = timestamp;
+			this.csv = csv;
+		}
+
+		@Override
+		public int compareTo(@NonNull LogEntry another) {
+			return (int)(timestamp - another.timestamp);
+		}
+	}
+
+	private class WriteBackWorker extends Thread {
+
+		public WriteBackWorker() {
+			setName("WriteBackWorker");
+			setPriority(Thread.MIN_PRIORITY);
+		}
+
+		@Override
+		public void run() {
+			try {
+				boolean stop = false;
+				while(!stop) {
+					flushSemaphore.acquireUninterruptibly();
+
+					LogEntry[] entriesToFlush = null;
+					synchronized (reorderBuffer) {
+                        int flushBatchSize = 1 + flushSemaphore.drainPermits(); // might contain extra-permit for stop-unblocking
+						if(flushBatchSize > reorderBuffer.size()) { // We were unblocked more than there are available lines to fush -> request to flush all & stop
+							stop = true;
+							flushBatchSize = reorderBuffer.size();
+						}
+						entriesToFlush = new LogEntry[flushBatchSize];
+
+						for(int i = 0; i < flushBatchSize; ++i) {
+							entriesToFlush[i] = reorderBuffer.poll();
+							currentSize -= entriesToFlush[i].csv.length();
+						}
+					}
+
+					for(int i = 0; i < entriesToFlush.length; ++i) {
+						fos.write(entriesToFlush[i].csv.getBytes());
+					}
+				}
+			} catch (IOException e) {
+				e.printStackTrace();
+			}
+		}
+	}
+
+
 }
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivity.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivity.java
index 1e7042b..0fc4291 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivity.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivity.java
@@ -12,6 +12,7 @@ public enum PedestrianActivity {
     STAIRS_DOWN(3),
     ELEVATOR_UP(4),
     ELEVATOR_DOWN(5),
+    MESS_AROUND(6),
     ;
 
     private int id;
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivityButton.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivityButton.java
index 288732f..7d13aab 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivityButton.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PedestrianActivityButton.java
@@ -1,35 +1,45 @@
 package de.fhws.indoor.sensorreadout.sensors;
 
+import android.content.Context;
 import android.graphics.Color;
+import android.support.annotation.DrawableRes;
 import android.view.View;
+import android.widget.ImageView;
 import android.widget.LinearLayout;
+import android.widget.TextView;
+
+import de.fhws.indoor.sensorreadout.R;
 
 /**
  * Created by toni on 10/01/18.
+ * Extended by Markus on 19/06/19
  */
 
-public class PedestrianActivityButton {
+public class PedestrianActivityButton extends LinearLayout {
 
-    private LinearLayout btn;
-    private boolean isActivated = false;
-    private PedestrianActivity whatActivity;
+    private LinearLayout innerBtn;
+    private boolean isActive = false;
+    private PedestrianActivity activity;
 
-    public PedestrianActivityButton(LinearLayout btn, PedestrianActivity act){
-        this.btn = btn;
-        this.whatActivity = act;
+    public PedestrianActivityButton(Context context, PedestrianActivity activity, @DrawableRes int imageId) {
+        super(context);
+        inflate(getContext(), R.layout.pedestrian_activity_button, this);
+        this.activity = activity;
+        // setup ui
+        ImageView imageView = (ImageView)this.findViewById(R.id.activityButtonImage);
+        imageView.setImageResource(imageId);
+        TextView textView = (TextView)this.findViewById(R.id.activityButtonText);
+        textView.setText(activity.toString());
+        innerBtn = (LinearLayout)getChildAt(0);
+        setActivity(false);
     }
 
-    public void toggleActivity(){
-        isActivated = !isActivated;
-
-        if(isActivated){
-            btn.setBackgroundColor(Color.parseColor("#F9D737"));
-        } else {
-            btn.setBackgroundColor(Color.parseColor("#B2B2B2"));
-        }
+    public void setActivity(boolean active) {
+        this.isActive = active;
+        innerBtn.setBackgroundColor(Color.parseColor(
+                (isActive) ? "#F9D737" : "#B2B2B2"
+        ));
     }
 
-    public LinearLayout getLayout(){
-        return btn;
-    }
+    public PedestrianActivity getPedestrianActivity() { return this.activity; }
 }
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PhoneSensors.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PhoneSensors.java
index 0103455..ebd04e9 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PhoneSensors.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/PhoneSensors.java
@@ -39,6 +39,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 	private Sensor rotationVector;
 	private Sensor light;
 	private Sensor temperature;
+	private Sensor gameRotationVector;
 
 	/** local gravity copy (needed for orientation matrix) */
     private float[] mGravity = new float[3];
@@ -65,6 +66,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 		rotationVector = sensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR);
 		light = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
 		temperature = sensorManager.getDefaultSensor(Sensor.TYPE_AMBIENT_TEMPERATURE);
+		gameRotationVector = sensorManager.getDefaultSensor(Sensor.TYPE_GAME_ROTATION_VECTOR);
 
 		// dump sensor-vendor info to file
 		dumpVendors(act);
@@ -102,6 +104,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 			dumpSensor(sb, SensorType.LIGHT, light);
 			dumpSensor(sb, SensorType.AMBIENT_TEMPERATURE, temperature);
 			dumpSensor(sb, SensorType.HEART_RATE, heart);
+			dumpSensor(sb, SensorType.GAME_ROTATION_VECTOR, gameRotationVector);
 
 			// write
 			fos.write(sb.toString().getBytes());
@@ -139,13 +142,12 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
     @Override
     public void onSensorChanged(SensorEvent event) {
 
-		/*
 		// to compare with the other orientation
 		if(event.sensor.getType() == Sensor.TYPE_ORIENTATION) {
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.ORIENTATION_OLD,
+					listener.onData(SensorType.ORIENTATION_OLD, event.timestamp,
 					Float.toString(event.values[0]) + ";" +
 					Float.toString(event.values[1]) + ";" +
 					Float.toString(event.values[2])
@@ -153,13 +155,12 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 			}
 
 		}
-		*/
 
 		if(event.sensor.getType() == Sensor.TYPE_HEART_RATE) {
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.HEART_RATE,
+				listener.onData(SensorType.HEART_RATE, event.timestamp,
 						Float.toString(event.values[0])
 				);
 			}
@@ -170,7 +171,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.LIGHT,
+				listener.onData(SensorType.LIGHT, event.timestamp,
 						Float.toString(event.values[0])
 				);
 			}
@@ -181,7 +182,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.AMBIENT_TEMPERATURE,
+				listener.onData(SensorType.AMBIENT_TEMPERATURE, event.timestamp,
 						Float.toString(event.values[0])
 				);
 			}
@@ -192,7 +193,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.RELATIVE_HUMIDITY,
+				listener.onData(SensorType.RELATIVE_HUMIDITY, event.timestamp,
 						Float.toString(event.values[0])
 				);
 			}
@@ -205,14 +206,14 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 			if (listener != null){
 
 				if(event.values.length > 3){
-					listener.onData(SensorType.ROTATION_VECTOR,
+					listener.onData(SensorType.ROTATION_VECTOR, event.timestamp,
 							Float.toString(event.values[0]) + ";" +
 							Float.toString(event.values[1]) + ";" +
 							Float.toString(event.values[2]) + ";" +
 							Float.toString(event.values[3])
 					);
 				} else {
-					listener.onData(SensorType.ROTATION_VECTOR,
+					listener.onData(SensorType.ROTATION_VECTOR, event.timestamp,
 							Float.toString(event.values[0]) + ";" +
 							Float.toString(event.values[1]) + ";" +
 							Float.toString(event.values[2])
@@ -227,7 +228,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.GYROSCOPE,
+				listener.onData(SensorType.GYROSCOPE, event.timestamp,
 					Float.toString(event.values[0]) + ";" +
 					Float.toString(event.values[1]) + ";" +
 					Float.toString(event.values[2])
@@ -240,7 +241,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.PRESSURE,
+				listener.onData(SensorType.PRESSURE, event.timestamp,
 					Float.toString(event.values[0])
 				);
 			}
@@ -251,10 +252,10 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.LINEAR_ACCELERATION,
+				listener.onData(SensorType.LINEAR_ACCELERATION, event.timestamp,
 					Float.toString(event.values[0]) + ";" +
 					Float.toString(event.values[1]) + ";" +
-					Float.toString(event.values[2]) + ";"
+					Float.toString(event.values[2])
 				);
 			}
 
@@ -264,7 +265,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
             if (listener != null){
-                listener.onData(SensorType.GRAVITY,
+                listener.onData(SensorType.GRAVITY, event.timestamp,
                         Float.toString(event.values[0]) + ";" +
                         Float.toString(event.values[1]) + ";" +
                         Float.toString(event.values[2])
@@ -277,7 +278,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
 			if (listener != null){
-				listener.onData(SensorType.ACCELEROMETER,
+				listener.onData(SensorType.ACCELEROMETER, event.timestamp,
 					Float.toString(event.values[0]) + ";" +
 					Float.toString(event.values[1]) + ";" +
 					Float.toString(event.values[2])
@@ -297,7 +298,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 
 			// inform listeners
             if (listener != null){
-                listener.onData(SensorType.MAGNETIC_FIELD,
+                listener.onData(SensorType.MAGNETIC_FIELD, event.timestamp,
                         Float.toString(event.values[0]) + ";" +
                         Float.toString(event.values[1]) + ";" +
                         Float.toString(event.values[2])
@@ -310,14 +311,25 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 			// NOTE
 			// @see TYPE_ACCELEROMETER
 			// only MAG updates the current orientation as MAG is usually slower than ACC and this reduces the file-footprint
-			updateOrientation();
+			updateOrientation(event.timestamp);
 
         }
 
+        else if(event.sensor.getType() == Sensor.TYPE_GAME_ROTATION_VECTOR) {
+        	// inform listeners
+        	if (listener != null) {
+        		listener.onData(SensorType.GAME_ROTATION_VECTOR, event.timestamp,
+						Float.toString(event.values[0]) + ";" +
+								Float.toString(event.values[1]) + ";" +
+								Float.toString(event.values[2])
+				);
+			}
+		}
+
     }
 
 	/** calculate orientation from acc and mag */
-	private void updateOrientation() {
+	private void updateOrientation(long timestamp) {
 
 		// skip orientation update if either grav or geo is missing
 		if (mGravity == null) {return;}
@@ -339,7 +351,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 		if (listener != null) {
 
 			// orientation vector
-			listener.onData(SensorType.ORIENTATION_NEW,
+			listener.onData(SensorType.ORIENTATION_NEW, timestamp,
 				Float.toString(orientationNew[0]) + ";" +
 				Float.toString(orientationNew[1]) + ";" +
 				Float.toString(orientationNew[2])
@@ -358,7 +370,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 			sb.append(R[8]);
 
 			//Write the whole rotationMatrix R into the Listener.
-			listener.onData(SensorType.ROTATION_MATRIX, sb.toString());
+			listener.onData(SensorType.ROTATION_MATRIX, timestamp, sb.toString());
 
 //				Float.toString(R[0]) + ";" +
 //				Float.toString(R[1]) + ";" +
@@ -403,6 +415,7 @@ public class PhoneSensors extends mySensor implements SensorEventListener{
 		registerIfPresent(rotationVector, SensorManager.SENSOR_DELAY_FASTEST);
 		registerIfPresent(light, SensorManager.SENSOR_DELAY_FASTEST);
 		registerIfPresent(temperature, SensorManager.SENSOR_DELAY_FASTEST);
+		registerIfPresent(gameRotationVector, SensorManager.SENSOR_DELAY_FASTEST);
 
     }
 
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/SensorType.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/SensorType.java
index d458d90..4a7830b 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/SensorType.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/SensorType.java
@@ -23,6 +23,7 @@ public enum SensorType {
     HEART_RATE(15),
     GPS(16),
     WIFIRTT(17),
+    GAME_ROTATION_VECTOR(18),
 
     PEDESTRIAN_ACTIVITY(50),
     GROUND_TRUTH(99),
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java
index cce8c67..b35bb57 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java
@@ -42,13 +42,15 @@ public class WiFi extends mySensor {
 				public void onReceive(Context context, Intent intent) {
 					final StringBuilder sb = new StringBuilder(1024);
 					final List<ScanResult> res = wifi.getScanResults();
+					long timestamp = System.currentTimeMillis();
 					for (final ScanResult sr : res) {
 						sb.append(Helper.stripMAC(sr.BSSID)).append(';');
 						sb.append(sr.frequency).append(';');
 						sb.append(sr.level).append(';');
+						timestamp = sr.timestamp;
 					}
 					if (listener != null && isReceiverRegistered) {
-						listener.onData(sb.toString());
+						listener.onData(timestamp, sb.toString());
 					}
 					startScan();
 					//Log.d("wifi", sb.toString());
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java
index 3cc2017..ea210f5 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java
@@ -48,7 +48,7 @@ public class iBeacon extends mySensor {
 			@Override public void onScanResult(int callbackType, android.bluetooth.le.ScanResult result) {
 				//Log.d("BT", device + " " + rssi);
 				if (listener != null) {
-					listener.onData(Helper.stripMAC(result.getDevice().getAddress()) + ";" + result.getRssi() + ";" + result.getScanRecord().getTxPowerLevel());
+					listener.onData(result.getTimestampNanos(), Helper.stripMAC(result.getDevice().getAddress()) + ";" + result.getRssi() + ";" + result.getScanRecord().getTxPowerLevel());
 				}
 			}
 		};
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java
index 725c9fd..a7688a2 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java
@@ -8,6 +8,7 @@ import android.bluetooth.BluetoothManager;
 import android.content.Context;
 import android.content.Intent;
 import android.content.pm.PackageManager;
+import android.os.SystemClock;
 import android.widget.Toast;
 
 /**
@@ -45,7 +46,7 @@ public class iBeaconOld extends mySensor {
             @Override public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
                 //Log.d("BT", device + " " + rssi);
                 if (listener != null) {
-                    listener.onData(Helper.stripMAC(device.getAddress()) + ";" + rssi);
+                    listener.onData(SystemClock.elapsedRealtimeNanos(), Helper.stripMAC(device.getAddress()) + ";" + rssi);
                 }
             }
         };
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/mySensor.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/mySensor.java
index f3c8381..015eb39 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/mySensor.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/mySensor.java
@@ -12,10 +12,10 @@ public abstract class mySensor {
 	/** listen for sensor events */
 	public interface SensorListener {
 
-		public void onData(final String csv);
+		public void onData(final long timestamp, final String csv);
 
 		/** received data from the given sensor */
-        public void onData(final SensorType id, final String csv);
+        public void onData(final SensorType id, final long timestamp, final String csv);
 
 	}
 
diff --git a/app/src/main/res/drawable/ic_mess_around.xml b/app/src/main/res/drawable/ic_mess_around.xml
new file mode 100644
index 0000000..8e0a806
--- /dev/null
+++ b/app/src/main/res/drawable/ic_mess_around.xml
@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M7.52,21.48C4.25,19.94 1.91,16.76 1.55,13L0.05,13C0.56,19.16 5.71,24 12,24l0.66,-0.03 -3.81,-3.81 -1.33,1.32zM8.41,14.96c-0.19,0 -0.37,-0.03 -0.52,-0.08 -0.16,-0.06 -0.29,-0.13 -0.4,-0.24 -0.11,-0.1 -0.2,-0.22 -0.26,-0.37 -0.06,-0.14 -0.09,-0.3 -0.09,-0.47h-1.3c0,0.36 0.07,0.68 0.21,0.95 0.14,0.27 0.33,0.5 0.56,0.69 0.24,0.18 0.51,0.32 0.82,0.41 0.3,0.1 0.62,0.15 0.96,0.15 0.37,0 0.72,-0.05 1.03,-0.15 0.32,-0.1 0.6,-0.25 0.83,-0.44s0.42,-0.43 0.55,-0.72c0.13,-0.29 0.2,-0.61 0.2,-0.97 0,-0.19 -0.02,-0.38 -0.07,-0.56 -0.05,-0.18 -0.12,-0.35 -0.23,-0.51 -0.1,-0.16 -0.24,-0.3 -0.4,-0.43 -0.17,-0.13 -0.37,-0.23 -0.61,-0.31 0.2,-0.09 0.37,-0.2 0.52,-0.33 0.15,-0.13 0.27,-0.27 0.37,-0.42 0.1,-0.15 0.17,-0.3 0.22,-0.46 0.05,-0.16 0.07,-0.32 0.07,-0.48 0,-0.36 -0.06,-0.68 -0.18,-0.96 -0.12,-0.28 -0.29,-0.51 -0.51,-0.69 -0.2,-0.19 -0.47,-0.33 -0.77,-0.43C9.1,8.05 8.76,8 8.39,8c-0.36,0 -0.69,0.05 -1,0.16 -0.3,0.11 -0.57,0.26 -0.79,0.45 -0.21,0.19 -0.38,0.41 -0.51,0.67 -0.12,0.26 -0.18,0.54 -0.18,0.85h1.3c0,-0.17 0.03,-0.32 0.09,-0.45s0.14,-0.25 0.25,-0.34c0.11,-0.09 0.23,-0.17 0.38,-0.22 0.15,-0.05 0.3,-0.08 0.48,-0.08 0.4,0 0.7,0.1 0.89,0.31 0.19,0.2 0.29,0.49 0.29,0.86 0,0.18 -0.03,0.34 -0.08,0.49 -0.05,0.15 -0.14,0.27 -0.25,0.37 -0.11,0.1 -0.25,0.18 -0.41,0.24 -0.16,0.06 -0.36,0.09 -0.58,0.09L7.5,11.4v1.03h0.77c0.22,0 0.42,0.02 0.6,0.07s0.33,0.13 0.45,0.23c0.12,0.11 0.22,0.24 0.29,0.4 0.07,0.16 0.1,0.35 0.1,0.57 0,0.41 -0.12,0.72 -0.35,0.93 -0.23,0.23 -0.55,0.33 -0.95,0.33zM16.96,9.04c-0.32,-0.33 -0.7,-0.59 -1.14,-0.77 -0.43,-0.18 -0.92,-0.27 -1.46,-0.27L12,8v8h2.3c0.55,0 1.06,-0.09 1.51,-0.27 0.45,-0.18 0.84,-0.43 1.16,-0.76 0.32,-0.33 0.57,-0.73 0.74,-1.19 0.17,-0.47 0.26,-0.99 0.26,-1.57v-0.4c0,-0.58 -0.09,-1.1 -0.26,-1.57 -0.18,-0.47 -0.43,-0.87 -0.75,-1.2zM16.57,12.2c0,0.42 -0.05,0.79 -0.14,1.13 -0.1,0.33 -0.24,0.62 -0.43,0.85 -0.19,0.23 -0.43,0.41 -0.71,0.53 -0.29,0.12 -0.62,0.18 -0.99,0.18h-0.91L13.39,9.12h0.97c0.72,0 1.27,0.23 1.64,0.69 0.38,0.46 0.57,1.12 0.57,1.99v0.4zM12,0l-0.66,0.03 3.81,3.81 1.33,-1.33c3.27,1.55 5.61,4.72 5.96,8.48h1.5C23.44,4.84 18.29,0 12,0z"/>
+</vector>
diff --git a/app/src/main/res/layout/activity_main.xml b/app/src/main/res/layout/activity_main.xml
index 83f3a3f..d1a9090 100644
--- a/app/src/main/res/layout/activity_main.xml
+++ b/app/src/main/res/layout/activity_main.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -62,8 +63,7 @@
                 android:background="#64bbe5" />
         </LinearLayout>
     </LinearLayout>
-
-
+    
     <TextView
         android:id="@+id/txtFile"
         android:layout_width="match_parent"
@@ -117,189 +117,15 @@
             android:textColor="#ffffff" />
     </LinearLayout>
 
-    <LinearLayout
-        android:id="@+id/layoutActivity1"
+
+    <TableLayout
+        android:id="@+id/pedestrianActivityButtonContainer"
         android:layout_width="match_parent"
-        android:layout_height="0dp"
-        android:layout_above="@+id/layoutGround"
-        android:layout_marginEnd="10dip"
+        android:layout_height="wrap_content"
+        android:layout_weight="2"/>
 
-        android:layout_marginTop="10dip"
-        android:layout_weight="1"
-        android:orientation="horizontal"
-        android:weightSum="3">
-
-        <LinearLayout
-            android:id="@+id/btnWalk"
-            android:layout_width="0dip"
-            android:layout_height="match_parent"
-            android:layout_marginStart="10dip"
-            android:layout_weight="1"
-            android:background="#B2B2B2"
-            android:orientation="vertical"
-            android:weightSum="3">
-
-            <ImageView
-                android:layout_marginTop="10dip"
-                android:layout_width="match_parent"
-                android:layout_height="0dip"
-                android:layout_weight="2"
-                android:src="@drawable/ic_walk" />
-
-            <TextView
-                android:layout_width="match_parent"
-                android:textStyle="bold"
-                android:layout_height="0dip"
-                android:layout_weight="1"
-                android:gravity="center"
-                android:text="Laufen" />
-        </LinearLayout>
-
-        <LinearLayout
-            android:id="@+id/btnStairsUp"
-            android:layout_width="0dip"
-            android:layout_height="match_parent"
-            android:layout_marginStart="10dip"
-            android:layout_weight="1"
-            android:background="#B2B2B2"
-            android:orientation="vertical"
-            android:weightSum="3">
-
-            <ImageView
-                android:layout_marginTop="10dip"
-                android:layout_width="match_parent"
-                android:layout_height="0dip"
-                android:layout_weight="2"
-                android:src="@drawable/ic_stairs_up" />
-
-            <TextView
-                android:layout_width="match_parent"
-                android:textStyle="bold"
-                android:layout_height="0dip"
-                android:layout_weight="1"
-                android:gravity="center"
-                android:text="Treppe rauf" />
-        </LinearLayout>
-
-        <LinearLayout
-            android:id="@+id/btnStairsDown"
-            android:layout_width="0dip"
-            android:layout_height="match_parent"
-            android:layout_marginStart="10dip"
-            android:layout_weight="1"
-            android:background="#B2B2B2"
-            android:orientation="vertical"
-            android:weightSum="3">
-
-            <ImageView
-                android:layout_marginTop="10dip"
-                android:layout_width="match_parent"
-                android:layout_height="0dip"
-                android:layout_weight="2"
-                android:src="@drawable/ic_stairs_down" />
-
-            <TextView
-                android:layout_width="match_parent"
-                android:textStyle="bold"
-                android:layout_height="0dip"
-                android:layout_weight="1"
-                android:gravity="center"
-                android:text="Treppe runter" />
-        </LinearLayout>
-
-    </LinearLayout>
 
     <LinearLayout
-        android:id="@+id/layoutActivity2"
-        android:layout_width="match_parent"
-        android:layout_height="0dp"
-        android:layout_above="@+id/layoutGround"
-        android:layout_marginEnd="10dip"
-        android:layout_marginTop="10dip"
-        android:layout_weight="1"
-        android:orientation="horizontal"
-        android:weightSum="3">
-
-        <LinearLayout
-            android:id="@+id/btnStanding"
-            android:layout_width="0dip"
-            android:layout_height="match_parent"
-            android:layout_marginStart="10dip"
-            android:layout_weight="1"
-            android:background="#B2B2B2"
-            android:orientation="vertical"
-            android:weightSum="3">
-
-            <ImageView
-                android:layout_marginTop="10dip"
-                android:layout_width="match_parent"
-                android:layout_height="0dip"
-                android:layout_weight="2"
-                android:src="@drawable/ic_standing" />
-
-            <TextView
-                android:layout_width="match_parent"
-                android:textStyle="bold"
-                android:layout_height="0dip"
-                android:layout_weight="1"
-                android:gravity="center"
-                android:text="Stehen" />
-        </LinearLayout>
-
-        <LinearLayout
-            android:id="@+id/btnElevatorUp"
-            android:layout_width="0dip"
-            android:layout_height="match_parent"
-            android:layout_marginStart="10dip"
-            android:layout_weight="1"
-            android:background="#B2B2B2"
-            android:orientation="vertical"
-            android:weightSum="3">
-
-            <ImageView
-                android:layout_width="match_parent"
-                android:layout_height="0dip"
-                android:layout_weight="2"
-                android:src="@drawable/ic_elevator_up" />
-
-            <TextView
-                android:layout_width="match_parent"
-                android:textStyle="bold"
-                android:layout_height="0dip"
-                android:layout_weight="1"
-                android:gravity="center"
-                android:text="Aufzug rauf" />
-        </LinearLayout>
-
-        <LinearLayout
-            android:id="@+id/btnElevatorDown"
-            android:layout_width="0dip"
-            android:layout_height="match_parent"
-            android:layout_marginStart="10dip"
-            android:layout_weight="1"
-            android:background="#B2B2B2"
-            android:orientation="vertical"
-            android:weightSum="3">
-
-            <ImageView
-                android:layout_width="match_parent"
-                android:layout_height="0dip"
-                android:layout_weight="2"
-                android:src="@drawable/ic_elevator_down" />
-
-            <TextView
-                android:layout_width="match_parent"
-                android:textStyle="bold"
-                android:layout_height="0dip"
-                android:layout_weight="1"
-                android:gravity="center"
-                android:text="Aufzug runter" />
-        </LinearLayout>
-
-
-    </LinearLayout>
-
-    <RelativeLayout
         android:id="@+id/layoutGround"
         android:layout_width="match_parent"
         android:layout_height="0dp"
@@ -309,9 +135,17 @@
 
         <Button
             android:id="@+id/btnGround"
-            android:layout_width="match_parent"
+            android:layout_width="wrap_content"
             android:layout_height="match_parent"
+            android:layout_weight="1"
             android:background="#64bbe5"
             android:text="Ground Truth" />
-    </RelativeLayout>
+
+        <Button
+            android:id="@+id/btnSettings"
+            android:layout_width="wrap_content"
+            android:layout_height="match_parent"
+            android:background="#bbb"
+            android:text="Settings" />
+    </LinearLayout>
 </LinearLayout>
diff --git a/app/src/main/res/layout/activity_settings.xml b/app/src/main/res/layout/activity_settings.xml
new file mode 100644
index 0000000..20873b7
--- /dev/null
+++ b/app/src/main/res/layout/activity_settings.xml
@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".SettingsActivity"
+    android:orientation="vertical">
+
+    <android.support.v7.widget.Toolbar
+        android:id="@+id/toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="?attr/actionBarSize"
+        android:background="?attr/colorPrimary"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:popupTheme="@style/AppTheme.PopupOverlay"
+        app:title="Settings" />
+
+</LinearLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/pedestrian_activity_button.xml b/app/src/main/res/layout/pedestrian_activity_button.xml
new file mode 100644
index 0000000..2179a4a
--- /dev/null
+++ b/app/src/main/res/layout/pedestrian_activity_button.xml
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:layout_weight="1"
+    android:orientation="vertical"
+    android:layout_margin="5dp"
+    android:weightSum="3">
+
+    <ImageView
+        android:id="@+id/activityButtonImage"
+        android:layout_marginTop="10dip"
+        android:layout_width="match_parent"
+        android:layout_height="0dip"
+        android:layout_weight="2" />
+
+    <TextView
+        android:id="@+id/activityButtonText"
+        android:layout_width="match_parent"
+        android:textStyle="bold"
+        android:layout_height="0dip"
+        android:layout_weight="1"
+        android:gravity="center" />
+
+</LinearLayout>
\ No newline at end of file
diff --git a/app/src/main/res/values/dimens.xml b/app/src/main/res/values/dimens.xml
index 47c8224..812cb7b 100644
--- a/app/src/main/res/values/dimens.xml
+++ b/app/src/main/res/values/dimens.xml
@@ -2,4 +2,5 @@
     <!-- Default screen margins, per the Android Design guidelines. -->
     <dimen name="activity_horizontal_margin">16dp</dimen>
     <dimen name="activity_vertical_margin">16dp</dimen>
+    <dimen name="fab_margin">16dp</dimen>
 </resources>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index d4b74c2..b278592 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -5,4 +5,46 @@
     <string name="hello_world">Hello world!</string>
     <string name="action_settings">Settings</string>
 
+    <string name="prefActiveSensors">Active Sensors</string>
+    <string name="prefActiveSensorsSummary">Choose the sensors included in the recording</string>
+    <string-array name="prefActiveSensorsEntries">
+        <item>GPS</item>
+        <item>WiFi</item>
+        <item>Bluetooth</item>
+        <item>Phone (Accel, Gyro, Magnet)</item>
+    </string-array>
+    <string-array name="prefActiveSensorsValues">
+        <item>GPS</item>
+        <item>WIFI</item>
+        <item>BLUETOOTH</item>
+        <item>PHONE</item>
+    </string-array>
+    <string-array name="prefActiveSensorsDefault">
+        <item>GPS</item>
+        <item>WIFI</item>
+        <item>BLUETOOTH</item>
+        <item>PHONE</item>
+    </string-array>
+
+    <string name="prefActiveActions">Active Pedestrian-Actions</string>
+    <string name="prefActiveActionsSummary">Choose which Pedestrian-Actions should be available to choose from during recording.</string>
+    <string-array name="prefActiveActionsEntries">
+        <item>Walk</item>
+        <item>Elevator Up/Down</item>
+        <item>Stairs Up/Down</item>
+        <item>Messing Around</item>
+    </string-array>
+    <string-array name="prefActiveActionsValues">
+        <item>WALK</item>
+        <item>ELEVATOR</item>
+        <item>STAIRS</item>
+        <item>MESS_AROUND</item>
+    </string-array>
+    <string-array name="prefActiveActionsDefault">
+        <item>WALK</item>
+        <item>ELEVATOR</item>
+        <item>STAIRS</item>
+        <item>MESS_AROUND</item>
+    </string-array>
+
 </resources>
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index 319eb0c..3e92110 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -5,4 +5,13 @@
         <!-- Customize your theme here. -->
     </style>
 
+    <style name="AppTheme.NoActionBar">
+        <item name="windowActionBar">false</item>
+        <item name="windowNoTitle">true</item>
+    </style>
+
+    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
+
+    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />
+
 </resources>
diff --git a/app/src/main/res/xml/preferences.xml b/app/src/main/res/xml/preferences.xml
new file mode 100644
index 0000000..5d6ad7b
--- /dev/null
+++ b/app/src/main/res/xml/preferences.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <MultiSelectListPreference
+        android:entries="@array/prefActiveSensorsEntries"
+        android:entryValues="@array/prefActiveSensorsValues"
+        android:defaultValue="@array/prefActiveSensorsDefault"
+        android:key="prefActiveSensors"
+        android:summary="@string/prefActiveSensorsSummary"
+        android:title="@string/prefActiveSensors" />
+    <MultiSelectListPreference
+        android:entries="@array/prefActiveActionsEntries"
+        android:entryValues="@array/prefActiveActionsValues"
+        android:defaultValue="@array/prefActiveActionsDefault"
+        android:key="prefActiveActions"
+        android:summary="@string/prefActiveActionsSummary"
+        android:title="@string/prefActiveActions" />
+
+</PreferenceScreen>
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index 399e18e..9d5ad52 100644
--- a/build.gradle
+++ b/build.gradle
@@ -8,9 +8,10 @@ buildscript {
             url 'https://maven.google.com/'
             name 'Google'
         }
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0'
+        classpath 'com.android.tools.build:gradle:3.1.0'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 76010aa..b3f6adc 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Mon Nov 13 09:30:52 CET 2017
+#Tue Jun 18 22:08:40 CEST 2019
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.2-all.zip

From e344fbbfefd5e963a2182ef8985bb9d59f9a5083 Mon Sep 17 00:00:00 2001
From: kazu <support@frank-ebner.de>
Date: Thu, 22 Aug 2019 12:39:00 +0200
Subject: [PATCH 2/2] fixed issue with Timestamp sorting added new RAM-only
 logger fixed issue with WiFi timestamps

---
 app/build.gradle                              |   7 +-
 .../indoor/sensorreadout/MainActivity.java    |  68 ++++---
 .../indoor/sensorreadout/sensors/Logger.java  |   2 +-
 .../sensorreadout/sensors/LoggerRAM.java      | 171 ++++++++++++++++++
 .../indoor/sensorreadout/sensors/WiFi.java    |  35 ++--
 .../indoor/sensorreadout/sensors/iBeacon.java |   2 +-
 .../sensorreadout/sensors/iBeaconOld.java     |   5 +-
 build.gradle                                  |   2 +-
 gradle/wrapper/gradle-wrapper.properties      |   4 +-
 9 files changed, 248 insertions(+), 48 deletions(-)
 create mode 100644 app/src/main/java/de/fhws/indoor/sensorreadout/sensors/LoggerRAM.java

diff --git a/app/build.gradle b/app/build.gradle
index b2cc588..0b1ebf4 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -1,15 +1,16 @@
 apply plugin: 'com.android.application'
 
 android {
-    compileSdkVersion 23
-    buildToolsVersion '26.0.3'
+    compileSdkVersion 29
+    buildToolsVersion '29.0.2'
 
     defaultConfig {
         applicationId "de.fhws.indoor.sensorreadout"
-        minSdkVersion 21
+        minSdkVersion 19
         targetSdkVersion 23
         versionCode 1
         versionName "1.0"
+        multiDexEnabled true
     }
     buildTypes {
         release {
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java b/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java
index 03e182f..e8e6cb5 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/MainActivity.java
@@ -35,12 +35,12 @@ import java.util.Set;
 import de.fhws.indoor.sensorreadout.sensors.GpsNew;
 import de.fhws.indoor.sensorreadout.sensors.GroundTruth;
 import de.fhws.indoor.sensorreadout.sensors.Logger;
+import de.fhws.indoor.sensorreadout.sensors.LoggerRAM;
 import de.fhws.indoor.sensorreadout.sensors.PedestrianActivity;
 import de.fhws.indoor.sensorreadout.sensors.PedestrianActivityButton;
 import de.fhws.indoor.sensorreadout.sensors.PhoneSensors;
 import de.fhws.indoor.sensorreadout.sensors.WiFi;
 import de.fhws.indoor.sensorreadout.sensors.iBeacon;
-import de.fhws.indoor.sensorreadout.sensors.iBeaconOld;
 import de.fhws.indoor.sensorreadout.sensors.mySensor;
 import de.fhws.indoor.sensorreadout.sensors.SensorType;
 
@@ -53,7 +53,8 @@ public class MainActivity extends Activity {
     MediaPlayer mpFailure;
 
     private final ArrayList<mySensor> sensors = new ArrayList<mySensor>();
-    private final Logger logger = new Logger(this);
+    //private final Logger logger = new Logger(this);
+    private final LoggerRAM logger = new LoggerRAM(this);
     private Button btnStart;
     private Button btnStop;
     private Button btnGround;
@@ -250,29 +251,39 @@ public class MainActivity extends Activity {
 
         logger.addCSV(id, timestamp, csv);
 
-        runOnUiThread(new Runnable() {
-            @Override public void run() {
 
-                if (id == SensorType.WIFI) {
-                    final TextView txt = (TextView) findViewById(R.id.txtWifi);
-                    txt.setText( ((++loadCounterWifi % 2) == 0) ? "wi" : "WI");
-                } else if (id == SensorType.IBEACON){
-                    final TextView txt = (TextView) findViewById(R.id.txtBeacon);
-                    txt.setText( ((++loadCounterBeacon % 2) == 0) ? "ib" : "IB");
-                } else if (id == SensorType.GPS){
-                    final TextView txt = (TextView) findViewById(R.id.txtGPS);
-                    txt.setText( ((++loadCounterGPS % 2) == 0) ? "gps" : "GPS");}
+        // update UI for WIFI/BEACON/GPS
+        if (id == SensorType.WIFI || id == SensorType.IBEACON || id == SensorType.GPS) {
+            runOnUiThread(new Runnable() {
+                @Override
+                public void run() {
 
-                // dump buffer stats every x entries
-                if (++loadCounterAny % 250 == 0) {
+                    if (id == SensorType.WIFI) {
+                        final TextView txt = (TextView) findViewById(R.id.txtWifi);
+                        txt.setText(((++loadCounterWifi % 2) == 0) ? "wi" : "WI");
+                    } else if (id == SensorType.IBEACON) {
+                        final TextView txt = (TextView) findViewById(R.id.txtBeacon);
+                        txt.setText(((++loadCounterBeacon % 2) == 0) ? "ib" : "IB");
+                    } else if (id == SensorType.GPS) {
+                        final TextView txt = (TextView) findViewById(R.id.txtGPS);
+                        txt.setText(((++loadCounterGPS % 2) == 0) ? "gps" : "GPS");
+                    }
+                }
+            });
+        }
+
+        // dump buffer stats every x entries
+        if (++loadCounterAny % 250 == 0) {
+            runOnUiThread(new Runnable() {
+                @Override
+                public void run() {
                     final TextView txt = (TextView) findViewById(R.id.txtBuffer);
                     final float elapsedMinutes = (timestamp - logger.getStartTS()) / 1000.0f / 1000.0f / 1000.0f / 60.0f;
                     final int kBPerMin = (int) (logger.getTotalSize() / 1024.0f / elapsedMinutes);
-                    txt.setText( (logger.getCurrentBufferSize() / 1024) + "k, " + logger.getNumEntries() + ", " + kBPerMin + "kB/m");
+                    txt.setText((logger.getCurrentBufferSize() / 1024) + "k, " + logger.getNumEntries() + ", " + kBPerMin + "kB/m");
                 }
-
-            }
-        });
+            });
+        }
 
     }
 
@@ -439,7 +450,7 @@ public class MainActivity extends Activity {
             });
         }
         if(activeSensors.contains("WIFI")) {
-            // logo wifi using sensor number 8
+            // log wifi using sensor number 8
             final WiFi wifi = new WiFi(this);
             sensors.add(wifi);
             wifi.setListener(new mySensor.SensorListener() {
@@ -461,15 +472,18 @@ public class MainActivity extends Activity {
             final mySensor beacon;
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                 beacon = new iBeacon(this);
-            } else{
-                beacon = new iBeaconOld(this);
+            } else {
+                beacon = null;
+                //beacon = new iBeaconOld(this);
             }
 
-            sensors.add(beacon);
-            beacon.setListener(new mySensor.SensorListener() {
-                @Override public void onData(final long timestamp, final String csv) { add(SensorType.IBEACON, csv, timestamp); }
-                @Override public void onData(final SensorType id, final long timestamp, final String csv) {return; }
-            });
+            if (beacon != null) {
+                sensors.add(beacon);
+                beacon.setListener(new mySensor.SensorListener() {
+                    @Override public void onData(final long timestamp, final String csv) { add(SensorType.IBEACON, csv, timestamp); }
+                    @Override public void onData(final SensorType id, final long timestamp, final String csv) {return; }
+                });
+            }
         }
     }
 
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java
index b73da7a..264f1a8 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/Logger.java
@@ -166,7 +166,7 @@ public final class Logger {
 
 		@Override
 		public int compareTo(@NonNull LogEntry another) {
-			return (int)(timestamp - another.timestamp);
+			return (timestamp < another.timestamp) ? (-1) : (+1);
 		}
 	}
 
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/LoggerRAM.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/LoggerRAM.java
new file mode 100644
index 0000000..417b298
--- /dev/null
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/LoggerRAM.java
@@ -0,0 +1,171 @@
+package de.fhws.indoor.sensorreadout.sensors;
+
+import android.content.Context;
+import android.os.SystemClock;
+import android.support.annotation.NonNull;
+import android.util.Log;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+
+/**
+ * log sensor data to RAM
+ * only flush to file when finished
+ */
+public final class LoggerRAM {
+
+    public static final long BEGINNING_TS = -1;
+
+
+    private StringBuilder stringBuilder = new StringBuilder();
+    private File file;
+    private FileOutputStream fos;
+    private Context context;
+
+    private boolean addingStopped = false;
+    private int entries = 0;
+    private int sizeTotal = 0;
+    private int currentSize = 0;
+
+    private ArrayList<LogEntry> buffer = new ArrayList<>();
+
+    /** timestamp of logging start. all entries are relative to this one */
+    private long startTS = 0;
+
+    public LoggerRAM(Context context) {
+        this.context = context;
+    }
+
+    /** start logging (into RAM) */
+    public final void start() {
+
+        // start empty
+        stringBuilder.setLength(0);
+        entries = 0;
+        sizeTotal = 0;
+        currentSize = 0;
+        buffer.clear();
+        addingStopped = false;
+
+        // starting timestamp
+        startTS = SystemClock.elapsedRealtimeNanos();
+
+        // open the output-file immeditaly (to get permission errors)
+        // but do NOT yet write anything to the file
+        final DataFolder folder = new DataFolder(context, "sensorOutFiles");
+        file = new File(folder.getFolder(), startTS + ".csv");
+
+        try {
+            fos = new FileOutputStream(file);
+            Log.d("logger", "will write to: " + file.toString());
+        } catch (final Exception e) {
+            throw new MyException("error while opening log-file", e);
+        }
+
+    }
+
+    /** stop logging and flush RAM-data to the flash-chip */
+    public final void stop() {
+
+        addingStopped = true;
+
+        synchronized (buffer) {
+
+            // sort by TS (ensure strict ordering)
+            Collections.sort(buffer);
+
+            // export each entry
+            for (LogEntry e : buffer) {
+                try {
+                    fos.write(e.csv.getBytes());
+                } catch (final Exception ex) {
+                    ex.printStackTrace();;
+                }
+            }
+
+            // done
+            buffer.clear();
+
+        }
+
+        // done
+        close();
+
+    }
+
+    public File getFile() {
+        return file;
+    }
+
+    public int getCurrentBufferSize() {return currentSize;}
+    public int getTotalSize() {return sizeTotal;}
+
+    public int getNumEntries() {return entries;}
+
+    /** add a new CSV entry for the given sensor number to the internal buffer */
+    public final void addCSV(final SensorType sensorNr, final long timestamp, final String csv) {
+
+        if (addingStopped) {return;}
+
+        final long relTS = (timestamp == BEGINNING_TS) ? 0 : (timestamp - startTS);
+        if(relTS >= 0) { // drop pre startTS logs (at the beginning, sensors sometimes deliver old values)
+
+            stringBuilder.setLength(0);
+            stringBuilder.append(relTS);	// relative timestamp (uses less space)
+            stringBuilder.append(';');
+            stringBuilder.append(sensorNr.id());
+            stringBuilder.append(';');
+            stringBuilder.append(csv);
+            stringBuilder.append('\n');
+            ++entries;
+            LogEntry logEntry = new LogEntry(relTS, stringBuilder.toString());
+            sizeTotal += logEntry.csv.length();
+            currentSize += logEntry.csv.length();
+
+            synchronized (buffer) {
+                buffer.add(logEntry);
+            }
+
+        }
+
+    }
+
+    private final void close() {
+        try {
+            fos.close();
+        } catch (final Exception e) {
+            throw new MyException("error while writing log-file", e);
+        }
+    }
+
+    public final long getStartTS() {
+        return startTS;
+    }
+
+    int cnt = 0;
+    private final void debug(boolean force) {
+        if (++cnt % 1000 == 0 || force) {
+            Log.d("buffer", "size: " + buffer.size() + " lines");
+        }
+    }
+
+
+
+    private static class LogEntry implements Comparable<LogEntry> {
+        public long timestamp;
+        public String csv;
+
+        public LogEntry(long timestamp, String csv) {
+            this.timestamp = timestamp;
+            this.csv = csv;
+        }
+
+        @Override
+        public int compareTo(@NonNull LogEntry another) {
+            return (timestamp < another.timestamp) ? (-1) : (+1);
+        }
+    }
+
+}
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java
index b35bb57..e0d57d1 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/WiFi.java
@@ -23,6 +23,7 @@ public class WiFi extends mySensor {
 	private final WifiManager wifi;
 	private BroadcastReceiver receiver;
     private boolean isReceiverRegistered;
+	private boolean isFirstMeasurement = true;
 
 	public WiFi(final Activity act) {
 
@@ -40,17 +41,29 @@ public class WiFi extends mySensor {
 			this.receiver = new BroadcastReceiver() {
 				@Override
 				public void onReceive(Context context, Intent intent) {
-					final StringBuilder sb = new StringBuilder(1024);
-					final List<ScanResult> res = wifi.getScanResults();
-					long timestamp = System.currentTimeMillis();
-					for (final ScanResult sr : res) {
-						sb.append(Helper.stripMAC(sr.BSSID)).append(';');
-						sb.append(sr.frequency).append(';');
-						sb.append(sr.level).append(';');
-						timestamp = sr.timestamp;
-					}
-					if (listener != null && isReceiverRegistered) {
-						listener.onData(timestamp, sb.toString());
+
+					// ignore the first measurement
+					if (isFirstMeasurement) {
+						isFirstMeasurement = false;
+					} else {
+						final StringBuilder sb = new StringBuilder(1024);
+						final List<ScanResult> res = wifi.getScanResults();
+						long timestamp = 0;
+						for (final ScanResult sr : res) {
+							sb.append(Helper.stripMAC(sr.BSSID)).append(';');
+							sb.append(sr.frequency).append(';');
+							sb.append(sr.level).append(';');
+
+							// export with oldest timestamp among all contained measurements
+							final long nanos = sr.timestamp * 1000;
+							if (nanos > timestamp) {
+								timestamp = nanos;
+							}
+
+						}
+						if (listener != null && isReceiverRegistered) {
+							listener.onData(timestamp, sb.toString());
+						}
 					}
 					startScan();
 					//Log.d("wifi", sb.toString());
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java
index ea210f5..9b78cdf 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeacon.java
@@ -20,7 +20,7 @@ public class iBeacon extends mySensor {
 	private static final int REQUEST_ENABLE_BT = 1;
 	private ScanCallback mLeScanCallback;
 
-	/** ctor */
+	// ctor
 	public iBeacon(final Activity act) {
 
 		// sanity check
diff --git a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java
index a7688a2..b190e7a 100644
--- a/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java
+++ b/app/src/main/java/de/fhws/indoor/sensorreadout/sensors/iBeaconOld.java
@@ -14,14 +14,14 @@ import android.widget.Toast;
 /**
  * Created by toni on 02/06/16.
  */
-
+/*
 public class iBeaconOld extends mySensor {
 
     private BluetoothAdapter bt = null;
     private static final int REQUEST_ENABLE_BT = 1;
     private BluetoothAdapter.LeScanCallback mLeScanCallback;
 
-    /** ctor */
+    // ctor
     public iBeaconOld(final Activity act) {
 
         // sanity check
@@ -70,3 +70,4 @@ public class iBeaconOld extends mySensor {
     }
 
 }
+*/
diff --git a/build.gradle b/build.gradle
index 9d5ad52..5d652f1 100644
--- a/build.gradle
+++ b/build.gradle
@@ -11,7 +11,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.1.0'
+        classpath 'com.android.tools.build:gradle:3.4.2'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index b3f6adc..de55c05 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Tue Jun 18 22:08:40 CEST 2019
+#Sun Aug 18 15:19:02 CEST 2019
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.2-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.1.1-all.zip