来自自定义图像视图的Toast消息

如何在扩展ImageView的类中显示toast消息。我想把它放在onDoubleTap方法中,这样它就会向用户显示一条消息,告诉用户刚刚双击了哪个像素。我有以下两个班:

public class TouchImageView extends ImageView 
{
  ....
   final GestureDetector mGestureDetector = new GestureDetector(new GestureDetector.SimpleOnGestureListener() 
    {
        @Override
        public boolean onDoubleTap(MotionEvent e) 
        {           
            Toast.makeText(getApplicationContext(), "Pixel",  Toast.LENGTH_SHORT).show();

            return true;
        }
        ...
   }

public class DisplayMap extends Activity 
{
  int width;
  int height;
  double imageSize;

  @Override
  public void onCreate(Bundle savedInstanceState) 
  {
    super.onCreate(savedInstanceState);

    TouchImageView img = new TouchImageView(getApplicationContext());

    Bitmap mapImage = BitmapFactory.decodeResource(getResources(), R.drawable.testimage);
    img.setImageBitmap(mapImage);
    img.setMaxZoom(4f);
    setContentView(img);
    ...
}

上面的代码不起作用,因为 ImageView的getApplicationContext()未定义。

谢谢