ios - UITextView text becomes invisible after height reaches 8192.0

Question

I have a non-scrollable UITextView embedded in a UIScrollView and add text to the UITextView dynamically. The UIScrollView adjust it's contentSize accordingly based on the TextView's frame. However, once the UITextView exceeds a height of 8192, the text will become invisible (but still there, because you can use the magnifying glass to highlight text and even see parts of the text through the magnifying glass).

  CGRect textviewFrame = self.TextView.frame;
  textviewFrame.size.height = [self textViewHeightForAttributedText:self.TextView.attributedText andWidth:320.0];
  self.TextView.frame = textviewFrame;
  self.ScrollView.contentSize = self.TextView.frame.size;

Helper function to size UITextView accordingly:

- (CGFloat)textViewHeightForAttributedText:(NSAttributedString *)text andWidth:(CGFloat)width
{
  UITextView *textView = [[UITextView alloc] init];
  [textView setAttributedText:text];
  CGSize size = [textView sizeThatFits:CGSizeMake(width, FLT_MAX)];
  return size.height;
}

Didn't realize it was the same exact problem that was unsolved here until I tested it out explicitly by forcing the max size to 8193 and the problem occurred (while a max size of 8192 still had the text showing correctly). Anyone run into this problem before and know of a work around? Thanks

Answer 1

I was recently hit by this problem and have worked out an effective way around it. Although it seems like an iOS bug IMHO it's really not... there are practical limits to CALayer sizes, plus drawing an 8K high piece of text takes a long time. Much better to do as Apple intended and to only render the bit of text that's visible... that's why UITextView extends UIScrollView after all.

The problem is that UITextView isn't terribly easy to integrate with other bits of UI. In my case I am working on a news app where a single UITextView is used to render the article, plus there's some separate UI (titles and buttons etc) above and below it, all hosted in a single scrollable container.

The solution I've found is to split the UITextView into two views... a dedicated UITextView container whose frame is the full text size (i.e. the same size your UITextView's contentSize) and which is the superview of your UITextView. Your child UITextView's frame should be set to the bounds of the outer scrollable container.

Then all you have to do is use key-value observation to monitor the contentOffset property of your outer scrollable container view (in my case this is a UICollectionView). When its contentOffset changes you update (1) the contentOffset of your UITextView, and (2) the transform property of the UITextView's layer. By updating that transform property the UITextView is fixed to fill the currently-visible part of it's superview. But because you're also updating the UITextView's contentOffset, this trickery is totally invisible to the user... it looks and behaves as if the UITextView is simply very large.