Marking Current Location on Map, Android

Question

I followed some tutorials to create an application that shows the current position of the user on the map with a marking. But for some reasons I can't get to work the marking part? The other parts work well, but whenever I add the marking code the application crashes.
Here is the code:

public class LocationActivity extends MapActivity {

    private MapView mapView;
    private LocationManager lm;
    private LocationListener ll;
    private MapController mc;
    GeoPoint p = null;
    Drawable defaultMarker = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mapView = (MapView) findViewById(R.id.mapView);
        // show zoom in/out buttons
        mapView.setBuiltInZoomControls(true);
        // Standard view of the map(map/sat)
        mapView.setSatellite(false);
        // get controller of the map for zooming in/out
        mc = mapView.getController();
        // Zoom Level
        mc.setZoom(18);
        MyLocationOverlay myLocationOverlay = new MyLocationOverlay();
        List<Overlay> list = mapView.getOverlays();
        list.add(myLocationOverlay);
        lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        ll = new MyLocationListener();
        lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, ll);
        // Get the current location in start-up
        GeoPoint initGeoPoint = new GeoPoint((int) (lm.getLastKnownLocation(
                LocationManager.GPS_PROVIDER).getLatitude() * 1000000),
                (int) (lm.getLastKnownLocation(LocationManager.GPS_PROVIDER)
                        .getLongitude() * 1000000));
        mc.animateTo(initGeoPoint);
    }

    protected class MyLocationOverlay extends com.google.android.maps.Overlay {

        @Override
        public boolean draw(Canvas canvas, MapView mapView, boolean shadow,
                long when) {
            Paint paint = new Paint();
            super.draw(canvas, mapView, shadow);
            // Converts lat/lng-Point to OUR coordinates on the screen.
            Point myScreenCoords = new Point();
            mapView.getProjection().toPixels(p, myScreenCoords);
            paint.setStrokeWidth(1);
            paint.setARGB(255, 255, 255, 255);
            paint.setStyle(Paint.Style.STROKE);
            Bitmap bmp = BitmapFactory.decodeResource(getResources(),
                    R.drawable.push);
            canvas.drawBitmap(bmp, myScreenCoords.x, myScreenCoords.y, paint);
            canvas.drawText("I am here...", myScreenCoords.x, myScreenCoords.y,
                    paint);
            return true;
        }
    }

    private class MyLocationListener implements LocationListener {

        public void onLocationChanged(Location argLocation) {
            GeoPoint myGeoPoint = new GeoPoint(
                    (int) (argLocation.getLatitude() * 1000000),
                    (int) (argLocation.getLongitude() * 1000000));
            /*
             * it will show a message on location change
             * Toast.makeText(getBaseContext(), "New location latitude ["
             * +argLocation.getLatitude() + "] longitude [" +
             * argLocation.getLongitude()+"]", Toast.LENGTH_SHORT).show();
             */
            mc.animateTo(myGeoPoint);
        }

        public void onProviderDisabled(String provider) {}

        public void onProviderEnabled(String provider) {}

        public void onStatusChanged(String provider, int status, Bundle extras) {}
    }

    protected boolean isRouteDisplayed() {
        return false;
    }
}

here is the logcat:

    01-19 05:31:43.011: DEBUG/AndroidRuntime(759): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<
01-19 05:31:43.011: DEBUG/AndroidRuntime(759): CheckJNI is ON
01-19 05:31:43.411: DEBUG/AndroidRuntime(759): --- registering native functions ---
01-19 05:31:43.431: INFO/jdwp(759): received file descriptor 19 from ADB
01-19 05:31:43.431: INFO/jdwp(759): Ignoring second debugger -- accepting and dropping
01-19 05:31:44.531: INFO/ActivityManager(583): Starting activity: Intent { flg=0x10000000 cmp=pro.googlemapp/.LocationActivity }
01-19 05:31:44.641: DEBUG/AndroidRuntime(759): Shutting down VM
01-19 05:31:44.641: DEBUG/dalvikvm(759): DestroyJavaVM waiting for non-daemon threads to exit
01-19 05:31:44.641: DEBUG/dalvikvm(759): DestroyJavaVM shutting VM down
01-19 05:31:44.641: DEBUG/dalvikvm(759): HeapWorker thread shutting down
01-19 05:31:44.651: DEBUG/dalvikvm(759): HeapWorker thread has shut down
01-19 05:31:44.651: DEBUG/jdwp(759): JDWP shutting down net...
01-19 05:31:44.651: DEBUG/jdwp(759): +++ peer disconnected
01-19 05:31:44.651: INFO/dalvikvm(759): Debugger has detached; object registry had 1 entries
01-19 05:31:44.661: DEBUG/dalvikvm(759): VM cleaning up
01-19 05:31:44.681: INFO/ActivityManager(583): Start proc pro.googlemapp for activity pro.googlemapp/.LocationActivity: pid=770 uid=10025 gids={3003}
01-19 05:31:44.761: DEBUG/dalvikvm(759): LinearAlloc 0x0 used 676436 of 4194304 (16%)
01-19 05:31:44.801: INFO/jdwp(770): received file descriptor 20 from ADB
01-19 05:31:44.822: INFO/dalvikvm(770): ignoring registerObject request in thread=3
01-19 05:31:44.851: INFO/jdwp(770): Ignoring second debugger -- accepting and dropping
01-19 05:31:44.851: ERROR/jdwp(770): Failed writing handshake bytes: Broken pipe (-1 of 14)
01-19 05:31:44.851: INFO/dalvikvm(770): Debugger has detached; object registry had 0 entries
01-19 05:31:45.320: ERROR/ActivityThread(770): Failed to find provider info for com.google.settings
01-19 05:31:45.320: ERROR/ActivityThread(770): Failed to find provider info for com.google.settings
01-19 05:31:45.340: ERROR/ActivityThread(770): Failed to find provider info for com.google.settings
01-19 05:31:45.781: DEBUG/LocationManager(770): Constructor: service = android.location.ILocationManager$Stub$Proxy@4379d9f0
01-19 05:31:45.791: WARN/GpsLocationProvider(583): Duplicate add listener for uid 10025
01-19 05:31:45.791: DEBUG/GpsLocationProvider(583): setMinTime 0
01-19 05:31:45.791: DEBUG/GpsLocationProvider(583): startNavigating
01-19 05:31:45.831: INFO/jdwp(770): received file descriptor 27 from ADB
01-19 05:31:46.001: INFO/MapActivity(770): Handling network change notification:CONNECTED
01-19 05:31:46.001: ERROR/MapActivity(770): Couldn't get connection factory client
01-19 05:31:46.451: DEBUG/dalvikvm(770): GC freed 4539 objects / 298952 bytes in 118ms
01-19 05:31:46.470: DEBUG/AndroidRuntime(770): Shutting down VM
01-19 05:31:46.470: WARN/dalvikvm(770): threadid=3: thread exiting with uncaught exception (group=0x4001aa28)
01-19 05:31:46.481: ERROR/AndroidRuntime(770): Uncaught handler: thread main exiting due to uncaught exception
01-19 05:31:46.541: ERROR/AndroidRuntime(770): java.lang.NullPointerException
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.google.android.maps.PixelConverter.toPixels(PixelConverter.java:58)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.google.android.maps.PixelConverter.toPixels(PixelConverter.java:48)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at pro.googlemapp.LocationActivity$MyLocationOverlay.draw(LocationActivity.java:101)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.google.android.maps.OverlayBundle.draw(OverlayBundle.java:42)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.google.android.maps.MapView.onDraw(MapView.java:476)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.View.draw(View.java:6274)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.View.draw(View.java:6277)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.widget.FrameLayout.draw(FrameLayout.java:352)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.View.draw(View.java:6277)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.widget.FrameLayout.draw(FrameLayout.java:352)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1883)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewRoot.draw(ViewRoot.java:1332)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1097)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1613)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.os.Looper.loop(Looper.java:123)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at android.app.ActivityThread.main(ActivityThread.java:4203)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at java.lang.reflect.Method.invokeNative(Native Method)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at java.lang.reflect.Method.invoke(Method.java:521)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
01-19 05:31:46.541: ERROR/AndroidRuntime(770):     at dalvik.system.NativeStart.main(Native Method)
01-19 05:31:46.551: INFO/Process(583): Sending signal. PID: 770 SIG: 3
01-19 05:31:46.581: INFO/dalvikvm(770): threadid=7: reacting to signal 3
01-19 05:31:46.661: INFO/dalvikvm(770): Wrote stack trace to '/data/anr/traces.txt'
01-19 05:31:46.871: INFO/ARMAssembler(583): generated scanline__00000077:03515104_00000000_00000000 [ 27 ipp] (41 ins) at [0x2c69c8:0x2c6a6c] in 973448 ns
01-19 05:31:46.911: INFO/ARMAssembler(583): generated scanline__00000077:03515104_00001001_00000000 [ 64 ipp] (84 ins) at [0x2c6a70:0x2c6bc0] in 1985378 ns
01-19 05:31:49.881: INFO/Process(770): Sending signal. PID: 770 SIG: 9
01-19 05:31:49.931: INFO/ActivityManager(583): Process pro.googlemapp (pid 770) has died.
01-19 05:31:49.941: WARN/GpsLocationProvider(583): Unneeded remove listener for uid 1000
01-19 05:31:49.941: DEBUG/GpsLocationProvider(583): stopNavigating
01-19 05:31:49.951: INFO/WindowManager(583): WIN DEATH: Window{438891c0 pro.googlemapp/pro.googlemapp.LocationActivity paused=false}
01-19 05:31:50.111: WARN/UsageStats(583): Unexpected resume of com.android.launcher while already resumed in pro.googlemapp
01-19 05:31:50.200: WARN/InputManagerService(583): Got RemoteException sending setActive(false) notification to pid 770 uid 10025

Answer 1

the way you construct the MyLocationOverlay might have some problem.

MyLocationOverlay mylocationOverlay = new MyLocationOverlay(this, mapView);

according to the google code api you need to pass a context and a mapview param.

and then put these code after that

mylocationOverlay.enableMyLocation();
mapView.getOverlays().add(locationOverlay);

also put

mylocationOverlay.enableMyLocation(); in the onResume() method

Hope this could help you.

Answer 2

The GeoPoint "p" in the MyLocationOverlay is null. When you replay "GeoPoint initGeoPoint" with "p" you can solve this problem.