Change the text of an attributed UILabel without losing the formatting?

问题

In the storyboard I layout a set of labels with various formatting options.

Then I do:

label.text = @"Set programmatically";

And all formatting is lost! This works fine in iOS5.

There must be a way of just updating the text string without recoding all the formatting?!

label.attributedText.string 

is read only.

Thanks in advance.

回答1:

An attributedString contains all of its formatting data. The label doesn't know anything about the formats at all.

You could possibly store the attributes as a separate dictionary and then when you change the attributedString you can use:

[[NSAttributedString alloc] initWithString:@"" attributes:attributes range:range];

The only other option is to build the attributes back up again.

回答2:

You can extract the attributes as a dictionary with:

NSDictionary *attributes = [(NSAttributedString *)label.attributedText attributesAtIndex:0 effectiveRange:NULL];

Then add them back with the new text:

label.attributedText = [[NSAttributedString alloc] initWithString:@"Some text" attributes:attributes];

This assumes the label has text in it, otherwise you'll crash so you should probably perform a check on that first with:

if ([self.label.attributedText length]) {...}

回答3:

Although new to iOS programming, I encountered the same problem very quickly. In iOS, my experience is that

1. Lewis42's problem occurs consistently
2. josef's suggestion of extracting and reapplying the attributes does not work: a null attributes dictionary is returned.

Having looked around s/o, I came across This Post and followed that recommendation, I ended up using this:

- (NSMutableAttributedString *)SetLabelAttributes:(NSString *)input col:(UIColor *)col size:(Size)size {

NSMutableAttributedString *labelAttributes = [[NSMutableAttributedString alloc] initWithString:input];

UIFont *font=[UIFont fontWithName:@"Helvetica Neue" size:size];

NSMutableParagraphStyle* style = [NSMutableParagraphStyle new];
style.alignment = NSTextAlignmentCenter;

[labelAttributes addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, labelAttributes.length)];
[labelAttributes addAttribute:NSParagraphStyleAttributeName value:style range:NSMakeRange(0, labelAttributes.length)];
[labelAttributes addAttribute:NSForegroundColorAttributeName value:col range:NSMakeRange(0, labelAttributes.length)];

return labelAttributes;

来源：https://stackoverflow.com/questions/12706188/change-the-text-of-an-attributed-uilabel-without-losing-the-formatting