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POError plotting coordinates from web service in Android
 

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  1. POError plotting coordinates from web service in Android
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    <p>I am writing an application that retrieves coordinates from a webservice, then plots them on a map together with my current location: I am able to write the code wich does not have any error but when i run it on the emulator it crashes....what could be the problem: Here is the code:</p> <pre><code>public abstract class MapActivity extends com.google.android.maps.MapActivity{ // Instance attributes private MapView mapView = null; private MapController mc = null; private GeoPoint p = null; private LocationManager locationManager; private LocationListener locationListener; @Override protected void onDestroy() { super.onDestroy(); } public boolean onKeyDown(int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_3: mc.zoomIn(); break; case KeyEvent.KEYCODE_1: mc.zoomOut(); break; } return super.onKeyDown(keyCode, event); } public void initMap(){ // Get the main element mapView = (MapView) findViewById(R.id.mapView); mc = mapView.getController(); // Add a zoom mapView.setBuiltInZoomControls(true); mapView.displayZoomControls(true); // Initialize the zoom level mc = mapView.getController(); mc.setZoom(17); //---Add a location marker--- MapOverlay mapOverlay = new MapOverlay(); List&lt;Overlay&gt; listOfOverlays = mapView.getOverlays(); listOfOverlays.clear(); listOfOverlays.add(mapOverlay); mapView.invalidate(); } public void drawElements(MapView mapView, Canvas canvas, String element){ if (mapView == null){ return; } try { // Get elements JSONObject elements = JSONfunctions.getJSONfromURL("http://10.0.2.2/android/rental.php"); JSONArray results = elements.getJSONArray("rental"); if (results != null &amp;&amp; results.length() != 0){ for (int i = 0; i &lt; elements.length(); i++) { JSONObject result = results.getJSONObject(i); //---fetch the coordinates from the remote server------ double lat = Double.parseDouble((String) result.get("lat")); double lon = Double.parseDouble((String) result.get("lon")); //---translate the GeoPoint to screen pixels--- Point screenPts = new Point(); GeoPoint p = new GeoPoint((int) (lat * 1E6), (int) (lon * 1E6)); mapView.getProjection().toPixels(p, screenPts); //---add the marker--- Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.red); canvas.drawBitmap(bmp, screenPts.x-20, screenPts.y-40, null); } } } catch (JSONException e) { Log.e(null,"JSONException error"); } } /** * Re-center the icon on the map */ public void refreshMapLocation(){ locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locationListener = new GPSLocationListener(); locationManager.requestLocationUpdates( LocationManager.GPS_PROVIDER,0, 0,locationListener); } private class GPSLocationListener implements LocationListener { @Override public void onLocationChanged(Location location) { GeoPoint p = new GeoPoint( (int) (location.getLatitude() * 1E6), (int) (location.getLongitude() * 1E6)); // Animate the map on the point if (p != null &amp;&amp; mc !=null){ mc.animateTo(p); } else { Log.e(null,"Couldn't refresh location on the map"); } } @Override public void onProviderDisabled(String provider) { } @Override public void onProviderEnabled(String provider) { } @Override public void onStatusChanged(String provider, int status, Bundle extras) { } } protected boolean isRouteDisplayed() { return false; } /** * Map overlay */ class MapOverlay extends com.google.android.maps.Overlay { @Override public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) { super.draw(canvas, mapView, shadow); if (p != null){ //---translate the GeoPoint to screen pixels--- Point screenPts = new Point(); mapView.getProjection().toPixels(p, screenPts); //---add the marker--- Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.blue); canvas.drawBitmap(bmp, screenPts.x-10, screenPts.y-20, null); } //drawElements(mapView,canvas,"Hospitals"); return true; } } } </code></pre> <p>edit.<em>*</em>* On looking at the error posted by Logcat this is what it has to say</p> <pre><code>11-20 09:10:31.931: I/Process(756): Sending signal. PID: 756 SIG: 9 11-20 09:39:57.001: D/dalvikvm(789): newInstance failed: p0 i0 [0 a1 11-20 09:39:57.001: D/AndroidRuntime(789): Shutting down VM 11-20 09:39:57.041: W/dalvikvm(789): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 11-20 09:39:57.091: E/AndroidRuntime(789): FATAL EXCEPTION: main 11-20 09:39:57.091: E/AndroidRuntime(789): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.jkuat.project/com.jkuat.project.MapActivity}: java.lang.InstantiationException: com.jkuat.project.MapActivity 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.os.Handler.dispatchMessage(Handler.java:99) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.os.Looper.loop(Looper.java:123) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.ActivityThread.main(ActivityThread.java:4627) 11-20 09:39:57.091: E/AndroidRuntime(789): at java.lang.reflect.Method.invokeNative(Native Method) 11-20 09:39:57.091: E/AndroidRuntime(789): at java.lang.reflect.Method.invoke(Method.java:521) 11-20 09:39:57.091: E/AndroidRuntime(789): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 11-20 09:39:57.091: E/AndroidRuntime(789): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 11-20 09:39:57.091: E/AndroidRuntime(789): at dalvik.system.NativeStart.main(Native Method) 11-20 09:39:57.091: E/AndroidRuntime(789): Caused by: java.lang.InstantiationException: com.jkuat.project.MapActivity 11-20 09:39:57.091: E/AndroidRuntime(789): at java.lang.Class.newInstanceImpl(Native Method) 11-20 09:39:57.091: E/AndroidRuntime(789): at java.lang.Class.newInstance(Class.java:1429) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 11-20 09:39:57.091: E/AndroidRuntime(789): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 11-20 09:39:57.091: E/AndroidRuntime(789): ... 11 more </code></pre>
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    1. USJames Wahome
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      1. VTUpMod
    1. COIf you're using Eclipse, open up the LogCat window under window->show view->other->android->LogCat. It prints out everything that's going on with the emulator/device as it's happening. Run your program again and when it crashes scroll through and look for a huge wall of red text. That's usually where your error occurs. That should give some more insight into your problem.
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      1. POError plotting coordinates from web service in Android
      1. USvince88
    2. COI already did that: this is what log cat has to say:
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      1. POError plotting coordinates from web service in Android
      1. USJames Wahome
 

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