我正在使用UITextView，可以通过点击“更多”按钮进行扩展。问题如下：
在 iOS6 上我使用这个，
self.DescriptionTextView.text = @"loong string";
if(self.DescriptionTextView.contentSize.height>self.DescriptionTextView.frame.size.height) {
//set up the more button
}
问题在于，在 iOS7 上，contentSize.height 返回的值与它在 iOS6 上返回的值不同（远小于）。
为什么是这样？如何解决？
【问题讨论】：
标签： ios objective-c cocoa-touch ios7 uitextview
内容大小属性不再像在 iOS 6 上那样工作。使用其他人建议的 sizeToFit 可能会或可能不会工作，具体取决于多种因素。
它对我不起作用，所以我改用它：
- (CGFloat)measureHeightOfUITextView:(UITextView *)textView
{
if (floor(NSFoundationVersionNumber) > NSFoundationVersionNumber_iOS_6_1)
{
// This is the code for iOS 7. contentSize no longer returns the correct value, so
// we have to calculate it.
//
// This is partly borrowed from HPGrowingTextView, but I've replaced the
// magic fudge factors with the calculated values (having worked out where
// they came from)
CGRect frame = textView.bounds;
// Take account of the padding added around the text.
UIEdgeInsets textContainerInsets = textView.textContainerInset;
UIEdgeInsets contentInsets = textView.contentInset;
CGFloat leftRightPadding = textContainerInsets.left + textContainerInsets.right + textView.textContainer.lineFragmentPadding * 2 + contentInsets.left + contentInsets.right;
CGFloat topBottomPadding = textContainerInsets.top + textContainerInsets.bottom + contentInsets.top + contentInsets.bottom;
frame.size.width -= leftRightPadding;
frame.size.height -= topBottomPadding;
NSString *textToMeasure = textView.text;
if ([textToMeasure hasSuffix:@"\n"])
{
textToMeasure = [NSString stringWithFormat:@"%@-", textView.text];
}
// NSString class method: boundingRectWithSize:options:attributes:context is
// available only on ios7.0 sdk.
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineBreakMode:NSLineBreakByWordWrapping];
NSDictionary *attributes = @{ NSFontAttributeName: textView.font, NSParagraphStyleAttributeName : paragraphStyle };
CGRect size = [textToMeasure boundingRectWithSize:CGSizeMake(CGRectGetWidth(frame), MAXFLOAT)
options:NSStringDrawingUsesLineFragmentOrigin
attributes:attributes
context:nil];
CGFloat measuredHeight = ceilf(CGRectGetHeight(size) + topBottomPadding);
return measuredHeight;
}
else
{
return textView.contentSize.height;
}
}
【讨论】：
试试下面链接的答案，layoutIfNeeded应该在contentSize之前调用。
iOS7 UITextView contentsize.height alternative
答案：
在 iOS7 中，UITextView 使用 NSLayoutManager 来布局文本：
// If YES, then the layout manager may perform glyph generation and layout for a given portion of the text, without having glyphs or layout for preceding portions. The default is NO. Turning this setting on will significantly alter which portions of the text will have glyph generation or layout performed when a given generation-causing method is invoked. It also gives significant performance benefits, especially for large documents.
@property(NS_NONATOMIC_IOSONLY) BOOL allowsNonContiguousLayout;
禁用allowsNonContiguousLayout 以修复contentSize：
textView.layoutManager.allowsNonContiguousLayout = NO;
【讨论】：
这个link 似乎有答案。
您必须先使用sizeToFit，然后才能使用contentSize。
【讨论】：
试试下面的代码，iOS6和7都可以，请试试看。
CGSize myTextViewSize = [self.myTextView sizeThatFits:CGSizeMake(self.myTextView.frame.size.width, FLT_MAX)];
self.myTextView.height = myTextViewSize.height;
NSLog(@"%f", self.myTextView.height);
【讨论】：