由於MapView導致的Activity崩潰

Question

我在嘗試顯示Android中的主Activity時遇到了一些麻煩。當Activity擴展MapView時，問題就開始了（我不知道爲什麼）。 LogCat顯示一些錯誤，但我不知道它們的意思。這裏是LogCat：

03-07 05:42:56.859: D/AndroidRuntime(15357): Shutting down VM 
03-07 05:42:56.859: W/dalvikvm(15357): threadid=1: thread exiting with uncaught exception (group=0x40018578) 
03-07 05:42:56.859: E/AndroidRuntime(15357): FATAL EXCEPTION: main 
03-07 05:42:56.859: E/AndroidRuntime(15357): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.geo.location/com.geo.location.GeoLocationActivity}: java.lang.IllegalArgumentException: listener==null 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.os.Handler.dispatchMessage(Handler.java:99) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.os.Looper.loop(Looper.java:130) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.ActivityThread.main(ActivityThread.java:3687) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at java.lang.reflect.Method.invokeNative(Native Method) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at java.lang.reflect.Method.invoke(Method.java:507) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at dalvik.system.NativeStart.main(Native Method) 
03-07 05:42:56.859: E/AndroidRuntime(15357): Caused by: java.lang.IllegalArgumentException: listener==null 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.location.LocationManager.requestLocationUpdates(LocationManager.java:444) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at com.geo.location.GeoLocationActivity.onCreate(GeoLocationActivity.java:64) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
03-07 05:42:56.859: E/AndroidRuntime(15357): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615) 
03-07 05:42:56.859: E/AndroidRuntime(15357): ... 11 more 

這是應用程序的代碼。

public class GeoLocationActivity extends MapActivity implements LocationListener { 
    private TextView lblLatitud; 
    private TextView lblLongitud; 
    private TextView lblPrecision; 
    private TextView lblEstado; 
    private TextView lblVelocidad; 
    private DecimalFormat df; 
    private MapView lblMapView; 
    private MapController mapController; 
    private LocationManager locManager; 
    private LocationListener locListener; 

    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     df = new DecimalFormat("#.########"); 
     lblLatitud = (TextView) findViewById(R.id.LblPosLatitud); 
     lblLongitud = (TextView) findViewById(R.id.LblPosLongitud); 
     lblPrecision = (TextView) findViewById(R.id.LblPosPrecision); 
     lblVelocidad = (TextView) findViewById(R.id.LblV); 
     lblEstado = (TextView) findViewById(R.id.textView8); 
     lblPrecision = (TextView) findViewById(R.id.LblPosPrecision); 
     lblMapView = (MapView) findViewById(R.id.mapview); 
     lblMapView.setBuiltInZoomControls(true); 

     lblLatitud.setText(""); 
     lblLongitud.setText(""); 
     lblPrecision.setText(""); 
     lblVelocidad.setText(""); 
     lblEstado.setText(""); 
     lblPrecision.setText(""); 

     locManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
     //Obtenemos la última posición conocida 
     Location loc = locManager.getLastKnownLocation(LocationManager.GPS_PROVIDER); 
     //Mostramos la última posición conocida 
     mostrarPosicion(loc); 
     locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locListener); 

    } 

    //Rellena los TextView de la Activity con la información básica de la posición 
    private void mostrarPosicion(Location loc) { 
     if(loc != null){ 
      lblLatitud.setText(String.valueOf(df.format(loc.getLatitude()))); 
      lblLongitud.setText(String.valueOf(df.format(loc.getLongitude()))); 
      lblPrecision.setText(String.valueOf(loc.getAccuracy())+ " metros"); 
      lblEstado.setText("GPS Ok"); 
      lblVelocidad.setText(String.valueOf(loc.getSpeed()*(3600/1000)) + "km/h <=> " + String.valueOf(loc.getSpeed()) + "m/s"); 
     }else{ 
      lblLatitud.setText("(sin_datos)"); 
      lblLongitud.setText("(sin_datos)"); 
      lblEstado.setText("(GPS no disponible)"); 
      lblPrecision.setText("(sin_datos)"); 
      lblVelocidad.setText("(sin_datos)"); 
     } 
    } 

    @Override 
    protected boolean isRouteDisplayed() { 
     return false; 
    } 

    //Añade un punto al array y muestra la posicion en el mapa 
    protected void updateLocation(Location location) { 
     GeoPoint point = new GeoPoint((int)(location.getLatitude() * 1E6), (int)(location.getLongitude() * 1E6)); 
     mapController = lblMapView.getController(); 
     mapController.animateTo(point); 
     mapController.setZoom(lblMapView.getMaxZoomLevel());  
     List<Overlay> mapOverlays = lblMapView.getOverlays(); 
     MiOverlay2 marker = new MiOverlay2(point, this); 
     mapOverlays.add(marker); 
     lblMapView.invalidate(); 
    } 

    public void onLocationChanged(Location location) { 
     lblEstado.setText("Gps Ok"); 
     mostrarPosicion(location); 
     updateLocation(location); 
    } 
    public void onProviderDisabled(String provider){ 
     lblEstado.setText("No connection"); 
     Intent intent = new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS); 
     startActivity(intent); 
    } 
    public void onProviderEnabled(String provider){ 
     lblEstado.setText("Gps Ok"); 
    } 
    public void onStatusChanged(String provider, int status, Bundle extras){ 
     Log.i("", "Provider Status: " + status); 
    } 
} 


/*********************************************************************** 
* CLASS:                * 
* OVERLAY QUE PINTA LAS FLECHAS EN LUGAR DONDE ESTA SITUADO EL USUARIO * 
***********************************************************************/ 
class MiOverlay extends Overlay { 
    GeoPoint punto; 
    Context ctxt; 

    public MiOverlay (GeoPoint punto, Context ctxt) { 
     super(); 
     this.punto = punto; 
     this.ctxt = ctxt; 
    } 

    @Override 
    public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) { 
     super.draw(canvas, mapView, shadow); 

     //se traduce el punto geo localizado a un punto en la pantalla 
     Point scrnPoint = new Point(); 
     mapView.getProjection().toPixels(punto, scrnPoint); 

     //se construye un bitmap a partir de la imagen 
     Bitmap marker = BitmapFactory.decodeResource(ctxt.getResources() , R.drawable.arrow); 

     //se dibuja la imagen del marker 
     canvas.drawBitmap(marker, 
       scrnPoint.x - marker.getWidth()/2, 
       scrnPoint.y - marker.getHeight(), 
       null); 
     return true; 
    } 
} 

正如你所看到的，這是一個非常簡單的程序，但是我找不到這個問題。

Answer 1

的LocationListener的，locListener，永遠不會被初始化，因此是無效...

locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locListener); 

Answer 2

使用以下

locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);