Question

How can I display a toast message from within a class which extends ImageView. I’d like to place it in the onDoubleTap method so it displays a message to the user as to what pixel was just double tapped. I have the following two classes:

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);
    ...
}

The code above won’t work because
getApplicationContext() is undefined for ImageView.

Thanks

Answer 1

Have your TouchImageView class a constructor that accepts a Context object.

Context context;

public TouchImageView(Context context) {
    super(context); //Thanks for this tip
    this.context = context;      
}

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

        return true;
    }
    ...
}

And send your Activity.this object in the TouchImageView object