如何使用自定义NSTextStorage清除UITextView？ [仅限iOS7]

Question

I'm currently trying to create an SMS-like screen, where the user can write some text and send it to other users. Everything goes as expected until I try to clear my text view and encounters a crash. I've been trying to find a way around this issue, but I just cannot find enough documentation online. So here it is, and hopefully one of you will know a fix for this.

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The implementation

My UITextView is a subclass of Peter Steinberger's implementation for iOS7 , and I use it with a custom NSTextStorage subclassed as showed in objc.io's 'Getting to Know TextKit' and especially that source code in order to highlight usernames in the message.

In my ViewController, I configure my text storage like this:

self.textStorage = [[[MyCustomTextStorage alloc] init] autorelease]; [self.textStorage addLayoutManager:self.textView.layoutManager];

And then in my TextView's delegate method:

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text

I store the input in my custom TextStorage:

[self.textStorage.string stringByReplacingCharactersInRange:range withString:text];

The crash

I can retrieve my text via self.textStorage.string , and then I clear my text view by replacing characters in the range of the input string. This works quite well, but when I try to set my TextView as the first responder again, the application crashes.

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSCFString _getBlockStart:end:contentsEnd:forRange:stopAtLineSeparators:]: Range {5, 0} out of bounds; string length 0'

The range mentioned is the range of my previously cleared string so it looks like I can clear the display, but my TextStorage / TextView is keeping a reference to the first edited range / string.

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Any idea on what could be causing this crash and how to resolve it? Thanks for your attention; at this point any help is appreciated, so please feel free to post if you have some piece of advice. :)

Answer 1

The reason it's crashing is because you are using a range that it outside the bounds of the string in the textStorage. If you want to clear the textView why not just use self.textStorage.string=@""

Answer 2

Same situation with you.

It costed me half a day to solve it.

1. The example you provide is right.

2. Your app will crash not only when you are clearing it, but also when using -setText: every time.

3. They don't crash beacause they would never call -setText: !!!

Solution:

add all TextKit staffs you need to your code,

like this:

_textStorage = [[NSTextStorage alloc] init];
_layoutManager = [[NSLayoutManager alloc] init];
[_textStorage addLayoutManager:_layoutManager];
_textContainer = [[NSTextContainer alloc] init];
[_layoutManager addTextContainer:_textContainer];
_myTextView = [[UITextView alloc] initWithFrame:frame textContainer:_textContainer];

Actually, you missed the NSTextContainer , so there's no right container for string to put in, then the app crashed.

Maybe you can send pull requests to these two demo project, for not miss leading other people.

Answer 3

替换文字后，请尝试：

[self setSelectedRange:NSMakeRange(0, 0)];