判斷view 是否顯示在scrollview 上

/*

• 判斷view 是否顯示在scrollview 上

• targetView 要判斷是否在scrollview 上顯示的targetView

• horizontalScroll scrollview 是橫向還是垂直滑動 ，yes 橫向 no 垂直

*/

• (BOOL)displayedInScreen:(UIView*)targetView horizontalScroll:(BOOL)horizontalScroll{

  BOOL show = YES;
  CGRect f = self.frame;
  if（horizontalScroll == YES）{
  f.origin.x = self.contentOffset.x;
  }else{
  f.origin.y = self.contentOffset.y;
  }
  CGRect r = [self.superview convertRect:targetView.frame toView:self.superview];
  if(CGRectIntersectsRect(f, r)) {
  // view is visible
  show = YES;
  }else
  show = NO;

  return show;

}