UITextView contentSize changes and NSLayoutManager in iOS7

Question

The problem: UITextView silently changes it\'s contentSize in some situations.

The simplest case textView with large text and keyboard. Just ad

Answer 1

Looks like the problem is in default layoutManager of UITextView. I've decided to subclass it and see, where and why re-layout being initiated. But simple creation of NSLayoutManager with default settings solved the problem.

Here is code (not perfect) from my demo project (see in question). The _textView there was an outlet, so I remove it from superview. This code is placed in - viewDidLoad:

NSTextStorage* textStorage = [[NSTextStorage alloc] initWithString:_textView.text];
NSLayoutManager* layoutManager = [NSLayoutManager new];
[textStorage addLayoutManager:layoutManager];
_textContainer = [[NSTextContainer alloc] initWithSize:self.view.bounds.size];
[layoutManager addTextContainer:_textContainer];
[_textView removeFromSuperview];    // remove original textView
_textView = [[MyTextView alloc] initWithFrame:self.view.bounds 
                                textContainer:_textContainer];
[self.view addSubview:_textView];

MyTextView here is a subclass of UITextView, see question for details.

For more info see:

• About Text Handling in iOS
• Using Text Kit to Draw and Manage Text
• NSLayoutManager Class Reference for iOS

Answer 2

I met a similar situation as urs. Mine shows with a different bug but due to the same reason: the contentSize property is silently changed by iOS7 incorrectly. Here is how I work around it. Its kinda a ugly fix. Whenever I need to use textView.contentSize, I calculate it by myself.

-(CGSize)sizeOfText:(NSString *)textToMesure widthOfTextView:(CGFloat)width withFont:(UIFont*)font
{
    CGSize size = [textToMesure sizeWithFont:font constrainedToSize:CGSizeMake(width-20.0, FLT_MAX) lineBreakMode:NSLineBreakByWordWrapping];
    return size;
}

then you can just call this function to get the size:

CGSize cont_size =   [self sizeOfText:self.text widthOfTextView:self.frame.size.width withFont:[UIFont systemFontOfSize:15]];

then, don't do the following:

self.contentSize = cont_size;// it causes iOS halt occasionally.

so, just use cont_size directly. I believe it's bug in iOS7 for now. Hopefully apple will fix it soon. Hope this is helpful.

Answer 3

Seems the bug in iOS7. At the time of input text content area behavior is wired in iOS7, It works fine with lower iOS7 version.

I have added below delegate method of UITextView to resolved this issue :

- (void)textViewDidChange:(UITextView *)textView {
CGRect line = [textView caretRectForPosition:
    textView.selectedTextRange.start];
CGFloat overflow = line.origin.y + line.size.height
    - ( textView.contentOffset.y + textView.bounds.size.height
    - textView.contentInset.bottom - textView.contentInset.top );
if ( overflow > 0 ) {
// We are at the bottom of the visible text and introduced a line feed, scroll down (iOS 7 does not do it)
// Scroll caret to visible area
    CGPoint offset = textView.contentOffset;
    offset.y += overflow + 7; // leave 7 pixels margin
// Cannot animate with setContentOffset:animated: or caret will not appear
    [UIView animateWithDuration:.2 animations:^{
        [textView setContentOffset:offset];
    }];
}