code: private boolean handleDownEvent(@NonNull final MotionEvent event) {
          mDownX = event.getRawX();
          mDownY = event.getRawY();
          return true;
      }
docs: Handles the down event.
  <p/>
  Finds the position and {@code View} of the touch point and, if allowed by the {@link com.nhaarman.listviewanimations.itemmanipulation.dragdrop.DraggableManager},
  starts dragging the {@code View}.
  
  @param event the {@link android.view.MotionEvent} that was triggered.
  
  @return {@code true} if we have started dragging, {@code false} otherwise.