Question

I am trying to develop a musical instrument app in android. I implemented OnTouchListener for every button, and there is no problem when I just touch one button. But when I touch a button and move my finger to the next one, the OnTouchListener for that button is not called and its sound not playing. How can I manage to play sounds during sliding my finger on the buttons without taking my finger up?
(I read many questions but they aren’t useful)

my simple OnTouchListener for each button:

final ImageButton img_1 = (ImageButton) findViewById(R.id.img_1);
img_1.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
              if( event.getAction() ==  MotionEvent.ACTION_DOWN )   {
                snd.play_s_l_1(); 
              }
             return true;
        } 

 });

Answer 1

Check the MotionEvent.MOVE:

private Rect rect;    // Variable rect to hold the bounds of the view

public boolean onTouch(View v, MotionEvent event) 
{
    if(event.getAction() == MotionEvent.ACTION_DOWN)
    {
        // Construct a rect of the view's bounds
        rect = new Rect(v.getLeft(), v.getTop(), v.getRight(), v.getBottom());
    }
    if(event.getAction() == MotionEvent.ACTION_MOVE)
    {
        if(!rect.contains((int)event.getX(), (int)event.getY()))
        {
            // User moved outside bounds
        }
    }
    return false;
}