Android detect double finger long press

Question

I'm creating an aplication where I can draw on a picture. Drawing is achieved by a pictureView, canvas with a bitmap and a onTouchListener. I want to add a feature that will undo the last action when there is a two finger short press. I achieved it by doing this:

if(event.getActionMasked() == MotionEvent.ACTION_POINTER_UP ){
    //undo
}

And I want to undo all the drawing actions when there is a two finger long press. I tried something like this, but it will detect only once.

if(event.getActionMasked() == MotionEvent.ACTION_POINTER_DOWN ){
    numberOfDown++;
        if(numberOfDown>100){
            //undo
        }
}

How can I achieve what I want?

Answer 1

I'm not sure whether the action index starts at zero for the primary finger or the non-primary fingers, so you might need to flip these 0's to 1's.

if(event.getActionMasked() == MotionEvent.ACTION_POINTER_DOWN && event.getActionIndex()==0){
    mSecondFingerTimeDown = System.currentTimeMillis();
}

if(event.getActionMasked() == MotionEvent.ACTION_POINTER_UP && event.getActionIndex()==0 ){
    if ((System.currentTimeMillis()-mSecondFingerDownTime) >= LONG_PRESS_TIME_MILLIS)
        //long double-press action
    else
        //short double-press action
}