Detect touch on bitmap

Question

Greets,

Does anyone how I go about detecting when a user presses on a bitmap which is inside a canvas?

Thanks

Answer 1

This will detect a touch and check if it is not transparent. You need this if your bitmaps are not rectangles. myBitmap is just a simple container class I use.

private boolean clickOnBitmap(MyBitmap myBitmap, MotionEvent event) {
    float xEnd = myBitmap.originX() + myBitmap.width();
    float yEnd = myBitmap.originY() + myBitmap.height();;


    if ((event.getX() >= myBitmap.originX() && event.getX() <= xEnd) 
    && (event.getY() >= myBitmap.originY() && event.getY() <= yEnd) ) {
        int pixX = (int) (event.getX() - myBitmap.originX());
        int pixY = (int) (event.getY() - myBitmap.originY());
        if (!(myBitmap.getBitmap().getPixel(pixX, pixY) == 0)) {
            return true;
        } else {
            return false;
        }
    }
    return false;
}

This is the on touch code for completeness

    @Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            if (clickOnBitmap(dog, event)) {
                Toast.makeText(getContext(), "dog", Toast.LENGTH_SHORT).show();
            } else if (clickOnBitmap(mouse,event)) {
                Toast.makeText(getContext(), "mouse", Toast.LENGTH_SHORT).show();
            }
        return true;
        case MotionEvent.ACTION_OUTSIDE:
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            return true;
    }
    return false;
}