Question

I set OnTouchListener of an ImageView and implement onTouch method, but if the image is scaled using matrix, how do I calculate the location of the touch?

Or does the motion event automatically takes that into account when returning getX() and getY() ?

Answer 1

getX and getY will return the touch location in the ImageView’s coordinate system. If you’re looking for the point within the image’s coordinate system, you can use the inverse matrix of the matrix used by the ImageView. I’ve done something like the following:

// calculate inverse matrix
Matrix inverse = new Matrix();
imageView.getImageMatrix().invert(inverse);

// map touch point from ImageView to image
float[] touchPoint = new float[] {event.getX(), event.getY()};
inverse.mapPoints(touchPoint);
// touchPoint now contains x and y in image's coordinate system