void onShow(boolean startDragging){
  mLastTouchX=Float.NaN;
  mLastTouchY=Float.NaN;
  mDragScrollOffset=0.0f;
  mDragScrollOffsetRounded=0;
  mDragScrollingVelocity=0.0f;
  mIsSingleTapCanceled=false;
  if (startDragging)   mDragScrolling.start();
}

void onShow ( boolean startDragging ) { mLastTouchX = Float . NaN ; mLastTouchY = Float . NaN ; mDragScrollOffset = 0.0f ; mDragScrollOffsetRounded = 0 ; mDragScrollingVelocity = 0.0f ; mIsSingleTapCanceled = false ; if ( startDragging ) mDragScrolling . start ( ) ; }
sets up all the internal state to prepare for menu dragging .
