等待UITextView完成更新文本（iOS 7.1） [英] Waiting for UITextView to Finish Updating Text (iOS 7.1)

问题描述

我正在编程更新 UITextView 的 attributedText 。更新后，我想调用 setContentOffset ，以便滚动到新文本的位置。

使用以下代码，调试日志输出相同的值：

   - （void）appendToTextView：（NSString *）text 
 {
 CGFloat bottomOfCurrentContent = _pastedText.contentSize.height; 
 NSLog（@Bottom of content，before =％f，bottomOfCurrentContent）; 
 
 NSString * textViewText = text; 
 
 BOOL以前的HadText = _pastedText.text.length> 0; 
 if（previouslyHadText）{
 textViewText = [NSString stringWithFormat：@％@ \\\
％@，_pastedText.text，textViewText]; 
} 
 
 NSMutableParagraphStyle * paragraphStyle = [[NSMutableParagraphStyle alloc] init]; 
 paragraphStyle.lineSpacing = _lineSpacing; 
 NSDictionary * attribute = @ {NSParagraphStyleAttributeName：paragraphStyle，
 NSFontAttributeName：[UIFont systemFontOfSize：18.0]}; 
 
 _pastedText.attributedText = [[NSAttributedString alloc] initWithString：textViewText attributes：attribute]; 
 
 if（previouslyHadText）{
 CGFloat bottomOfNewContent = _pastedText.contentSize.height; 
 NSLog（@Bottom of content，after =％f，bottomOfNewContent）; 
 //设置内容偏移... 
} 
} 
  

例如，输出：

  2014-05-03 21：52：57.181 thisApp [7011： 60b]内容底部，之前= 244.000000 
 2014-05-03 21：52：57.182 thisApp [7011：60b]内容底部，之后= 244.000000 
  

如果我人为地等待文本视图完成更新，则内容将按预期报告...

  dispatch_after（dispatch_time（DISPATCH_TIME_NOW，（int64_t）（5.0 * NSEC_PER_SEC）），dispatch_get_main_queue（），^ {
 CGFloat bottomOfNewContent = _pastedText.contentSize.height; 
 NSLog （@Bottom of content，after =％f，bottomOfNewContent）; 
 //设置内容偏移... 
}）; 
  

输出：

  2014-05-03 23：12：39.694 thisApp [7050：60b]底部的内容，before = 244.000000 
 2014-05-03 23：12：44.698 thisApp [7050：60b]内容的底部，之后= 451.000000 
  

UITextView 的更新已完成？

更新： b

根据 indyfromoz 的建议，我可以通过代理方法 textViewDidChangeSelection 获得回调到文本视图。

如果我把日志语句放在那里：

   - （void）textViewDidChangeSelection：（UITextView *）textView 
 {
 CGFloat newContentHeight = textView.contentSize 。高度; 
 NSLog（@新内容的底部：％f，newContentHeight）; 
} 
  

内容高度报告与更新前相同...

我把这个问题放在 UITextView 的错误。

解决方案

插入新文本后，在 UITextView 中，您可以使用 scrollRangeToVisible （通常通过 textViewDidChangeSelection delegate方法）滚动文本视图的内容。 UITextView 在iOS 7中有一些错误，并有一个彼得讨论此文章的好文章和 Brent Simmons有一个近乎完美的解决方案用于在UITextView中滚动内容。

I'm programatically updating the attributedText of a UITextView. Following the update I want to call setContentOffset so that I can scroll to position the new text.

The problem I'm having is that there's a delay in the text view updating its text.

With the following code the debug log outputs the same value:

- (void)appendToTextView:(NSString*)text
{
    CGFloat bottomOfCurrentContent = _pastedText.contentSize.height;
    NSLog(@"Bottom of content, before = %f", bottomOfCurrentContent);

    NSString* textViewText = text;

    BOOL previouslyHadText = _pastedText.text.length > 0;
    if (previouslyHadText) {
        textViewText = [NSString stringWithFormat:@"%@\n%@", _pastedText.text, textViewText];
    }

    NSMutableParagraphStyle* paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineSpacing = _lineSpacing;
    NSDictionary *attribute = @{ NSParagraphStyleAttributeName : paragraphStyle,
                                 NSFontAttributeName : [UIFont systemFontOfSize:18.0] };

    _pastedText.attributedText = [[ NSAttributedString alloc] initWithString:textViewText attributes:attribute];

    if (previouslyHadText) {
        CGFloat bottomOfNewContent = _pastedText.contentSize.height;
        NSLog(@"Bottom of content, after = %f", bottomOfNewContent);
        // Set content offset...
    }
}

E.g., output:

2014-05-03 21:52:57.181 thisApp[7011:60b] Bottom of content, before = 244.000000
2014-05-03 21:52:57.182 thisApp[7011:60b] Bottom of content, after = 244.000000

If I artificially wait for the text view to complete its update the content is reported as expected...

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        CGFloat bottomOfNewContent = _pastedText.contentSize.height;
        NSLog(@"Bottom of content, after = %f", bottomOfNewContent);
        // Set content offset...
    });

Output:

2014-05-03 23:12:39.694 thisApp[7050:60b] Bottom of content, before = 244.000000
2014-05-03 23:12:44.698 thisApp[7050:60b] Bottom of content, after = 451.000000

So, how do I get updated when the UITextViews update has finished?

Update:

Based on the suggestion from indyfromoz, I can get a callback from the delegate method textViewDidChangeSelection, following a programatic update to the text view. However, when that delegate method is called, the text view still hasn't finished updating.

If I drop the log statement in there:

- (void)textViewDidChangeSelection:(UITextView *)textView
{    
    CGFloat newContentHeight = textView.contentSize.height;
    NSLog(@"bottom of new content: %f", newContentHeight);
}

The content height is reported the same as it was before the update...

I'm putting this down to a bug with UITextView. I'll work around it for now and look at the code again in the future.

解决方案

After the insertion of the new text in your UITextView, you can use scrollRangeToVisible (Typically through the textViewDidChangeSelection delegate method) to scroll the text view's content. UITextView in iOS 7 has some bugs and there is a good article by Peter discussing this and Brent Simmons has a near perfect solution for scrolling content in UITextView.

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