onTouchEvent method for the PianoView on the SSaurel's Channel

PianoView.java

@Override
public boolean onTouchEvent(MotionEvent event) {
  int action = event.getAction();
  boolean isDownAction = action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_MOVE;

  for (int touchIndex = 0; touchIndex < event.getPointerCount(); touchIndex++) {
    float x = event.getX(touchIndex);
    float y = event.getY(touchIndex);

    Key k = keyForCoords(x,y);

    if (k != null) {
      k.down = isDownAction;
    }
  }

  ArrayList<Key> tmp = new ArrayList<>(whites);
  tmp.addAll(blacks);

  for (Key k : tmp) {
    if (k.down) {
      if (!soundPlayer.isNotePlaying(k.sound)) {
        soundPlayer.playNote(k.sound);
        invalidate();
      } else {
        releaseKey(k);
      }
    } else {
      soundPlayer.stopNote(k.sound);
      releaseKey(k);
    }
  }

  return true;
}