Question

I’ve got a SurfaceView, where I’m painting a circle. I know the position and the radius of the circle.

I need to know whether the circle is being pressed by the user. The user may being tapping the screen with one or two fingers. If any of the fingers is over the area of the circle, it has to be pressed.

When the user raises the finger from the screen, and there are no longer fingers over the circle, the circle has to stop being pressed.

I’ve got no problems when the user has only one finger on the screen, but I cannot resolve the problem when he’s using two fingers.

The problem I have is that when I receive an ACTION_UP or ACTION_POINTER_UP action, I don’t know which pointer is no longer on screen, so I don’t have to look if their coordinates are over the circle.

I’ve done several tries without success, last one is:

protected boolean checkPressed(MotionEvent event) {

    ColourTouchWorld w = (ColourTouchWorld)gameWorld;

    int actionMasked = event.getActionMasked();

    for (int i = 0; i < event.getPointerCount(); i++) {
        if (i == 0 && (actionMasked == MotionEvent.ACTION_UP || actionMasked == MotionEvent.ACTION_POINTER_UP)) {
            // the pointer with index 0 is no longer on screen, 
            // so the circle is not pressed by this pointer, even if
            // it's coordinates are over the area of the circle

            continue;
        }

        if (isPointInCicle(event.getX(i)), event.getY(i))) {
           return true;
        }
    }

    return false;
}

Any ideas? Thank you.

Answer 1

You need to use the ACTION_POINTER_INDEX_MASK constant. I have never implemented this so I don’t know how the code will look. But I think you’re going to need to use this.