private void updatePointersOnMove(MotionEvent event) {
    for (int i = 0; i < MAX_POINTERS; i++) {
      int index = event.findPointerIndex(mId[i]);
      if (index != -1) {
        mCurrentX[i] = event.getX(index);
        mCurrentY[i] = event.getY(index);
      }
    }
  }
Gets the number of pressed pointers (fingers down).
samples/gestures/src/main/java/com/facebook/samples/gestures/MultiPointerGestureDetector.java