显示可滚动项目Objective-C
对于我的应用程序,我有一个UITextView,当有可滚动的内容时,我需要显示一个箭头 当您处于底部或无法滚动文本时,图像必须隐藏显示可滚动项目Objective-C,objective-c,scroll,uitextview,Objective C,Scroll,Uitextview,对于我的应用程序,我有一个UITextView,当有可滚动的内容时,我需要显示一个箭头 当您处于底部或无法滚动文本时,图像必须隐藏 - (void)scrollViewDidScroll:(UIScrollView *)scrollView { self.scrollableItem.hidden = YES; float scrollViewHeight = scrollView.frame.size.height; float scrollContentSizeHeigh
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
self.scrollableItem.hidden = YES;
float scrollViewHeight = scrollView.frame.size.height;
float scrollContentSizeHeight = scrollView.contentSize.height;
float scrollOffset = scrollView.contentOffset.y;
if (scrollOffset > 0 && scrollOffset <= scrollViewHeight / 2) {
self.scrollableItem.hidden = NO;
} else if (scrollOffset <= 0 && scrollContentSizeHeight >= scrollViewHeight) {
self.scrollableItem.hidden = NO;
}
}
-(无效)scrollViewDidScroll:(UIScrollView*)scrollView{
self.scrollableItem.hidden=是;
浮动scrollViewHeight=scrollView.frame.size.height;
float scrollContentSizeHeight=scrollView.contentSize.height;
float scrollOffset=scrollView.contentOffset.y;
如果(scrollOffset>0&&scrollOffset您的思路是正确的。我们只需要一个公式来描述所需的条件:有太多的文本,这些文本延伸到视图底部以下
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView != self.textView) return;
[self updateScrollableItem:(UITextView *)scrollView];
}
- (void)textViewDidChange:(UITextView *)textView {
[self updateScrollableItem:textView];
}
- (void)updateScrollableItem:(UITextView *)textView {
CGSize contentSize = textView.contentSize;
CGSize boundsSize = textView.bounds.size;
CGFloat contentOffsetY = textView.contentOffset.y;
BOOL excess = contentSize.height > boundsSize.height;
// notice the little fudge to make sure some portion of a line is above the bottom
BOOL bottom = contentOffsetY + textView.font.lineHeight * 1.5 > contentSize.height - boundsSize.height;
self.scrollableItem.hidden = !excess || bottom;
}
这是因为,对于给定字体,视图高度可能不是行高度的整数倍。多行一点似乎就可以了。效果很好!谢谢!