title: Android - can't access drawable nullpointer exception
body: <p>I've tried to mark multiple locations on my mapview. There is, a class extends from ItemizedOverlay. There is  a constructor for that which has two paramaters <code>(Drawable defaultMarker, Context c)</code> </p>
  
  <p>In the MapActivity where i have the mapview i tried to define a drawable which is necessary to create the itemized overlay object, but i always have </p>
  
  <pre><code>java.lang.NullPointerException  caused by this line:
  
  
  
  
  Drawable marker =this.getResources().getDrawable(R.drawable.pointer);
  </code></pre>
  
  <p>i've checked this variable with a syso and it doesn't seems null to me</p>
  
  <pre><code>I/System.out(430): android.graphics.drawable.BitmapDrawable@405ca538
  </code></pre>
  
  <p>I've tried to look after solutions. What i've found is that initalize the context in the constructor of the MapActivity</p>
  
  <p>than i've got the following error:</p>
  
  <pre><code>Unable to instantiate activity ComponentInfo: java.lang.InstantiationException
  
  
  
  MapController mc;
  GeoPoint p;
  MapView mapView;
  Location loc;
      boolean move = true;
  LocationManager mlocManager;
  LocationListener mlocListener = new MyLocationListener();
  
      Context c
  /* if constructor commented: nullpointer else instantiation exception */
  
  MapActivity(Context cc){
      this.c=cc;
  }
  
  
  Drawable marker =c.getResources().getDrawable(R.drawable.pointer);
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
  
      super.onCreate(savedInstanceState);
      System.out.println(this.getResources());
      mlocManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
      setContentView(R.layout.map);
      tv = (TextView) findViewById(R.id.textView1);
  
  
  
      mapView = (MapView) findViewById(R.id.mapv);
      mapView.setBuiltInZoomControls(true);
      mc = mapView.getController();
  
      p = new GeoPoint((int) (lat1 * 1E6), (int) (lon1 * 1E6));
  
      Button bck = (Button) findViewById(R.id.backBtn);
      bck.setOnClickListener(new View.OnClickListener() {
          public void onClick(View vi) {
              mc.animateTo(p);
  
          }
      });
  
      class MapOverlay extends com.google.android.maps.Overlay {
          public boolean draw(Canvas canvas, MapView mapView, boolean shadow,
                  long when) {
              super.draw(canvas, mapView, shadow);
              Point screenPts = new Point();
              mapView.getProjection().toPixels(p, screenPts);
              Bitmap bmp = BitmapFactory.decodeResource(getResources(),
                      R.drawable.pointer);
              canvas.drawBitmap(bmp, screenPts.x, screenPts.y - 50, null);
              return true;
          }
      }
  }
  </code></pre>