Android - How To Distinguish First Pointer And Second Pointer Move In Ontouchevent

I want handle a gesture in my activity. To do this i have override the public boolean onTouchEvent(MotionEvent MEvent) method on my Activity. The content looks like this: motionact

Solution 1:

Referring to the answer of Quintin Balsdon:

I have a similar thing in my code. I save the position of the finger1 in the ACTION_DOWN case, then when the finger2 move i see if the Y coordinate of the move is over the saved finger1 Y coordinate. If so the movement it's referred to the finger2 otherwise is referred to finger1 and i discard that in two finger mode.

If i try to draw a circle on my view in one finger mode i have got something like this: http://img208.imageshack.us/img208/8113/onefingercircle.jpg

If i try to draw a circle on my view in two finger mode i have got something like this: http://img256.imageshack.us/img256/6778/twofingercircle.jpg

So in one finger mode it work perfectly but not in two finger mode. I don't know if it's related to the phone multitouch handler or the touch screen. It can be only hardware related also or my misunderstanding of the API.

Solution 2:

This is managed by you as the developer. You are going to have to create some boolean variable to set (to true) when the "DOWN" action takes place and then unset (false) when the "UP" or "MOVE" motionevent occurs. In the code below, I maintain the coordinates when the "DOWN" even happens and make adjustments while the user moves around.

switch (e.Action) //e is a MotionEvent type
{
    case MotionEvent.ACTION_DOWN:
    {                        
        _prevx = e.getX();
        _prevy = e.getY();
    }
    break;
    case MotionEvent.ACTION_MOVE:
    {
        _xoffset += e.GetX() - _prevx;
        _yoffset += e.GetY() - _prevy;
        Invalidate();

        _prevx = e.GetX();
        _prevy = e.GetY();
    }
    break;
}

If you want to do multi-finger dragging you need to implement ScaleGestureDetector.OnScaleGestureListener (http://developer.android.com/reference/android/view/ScaleGestureDetector.OnScaleGestureListener.html)