performance enhancements

memory enhancements
prevent starting sensors more than once
fix for wifi lag issues
map scaling for huge buildings

_android/src/WiFi.java

@@ -18,7 +18,8 @@ public class WiFi {
     private static WifiManager manager;
     private static BroadcastReceiver receiver;
 
-
+	private static Thread tHeartbeat = null;
+	private static long lastScanStartTS = 0;
 
     /** called when a scan is completed successfully */
     public static native void onScanComplete(final byte[] result);
@@ -48,7 +49,28 @@ public class WiFi {
         act.registerReceiver(WiFi.receiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
 
         // start the first scan
-        triggerOneScan();
+		triggerOneScan();
+
+
+
+		// if the scan result takes longer than X milliseconds,
+		// trigger another-scan to ensure nothing is stuck
+		final Runnable r = new Runnable() {
+			public void run() {
+				while(true) {
+					final long ts = System.currentTimeMillis();
+					final long diff = ts - lastScanStartTS;
+					if (diff > 1000) { triggerOneScan(); }
+					try {Thread.sleep(200);} catch (final Exception e) {;}
+				}
+			}
+		};
+
+	    // start the heartbeat once
+		if (tHeartbeat == null) {
+			tHeartbeat = new Thread(r);
+			tHeartbeat.start();
+		}
 
 		return 1337;
 
@@ -91,6 +113,7 @@ public class WiFi {
 
         try {
             if(!manager.startScan()) {throw new RuntimeException("Cant start WiFi!");}
+			lastScanStartTS = System.currentTimeMillis();
         }catch (final Exception e) {
             throw new RuntimeException(e);
         }