Displaying NSMutableAttributedString on iOS 8

问题:

Seems on iOS 8.0 (12A365) NSMutableAttributedString sometimes will not be displayed correctly. The problem obviously occurs when the range of the attribute does not start at the beginning of the text (and if there is no other attribute starting at the beginning of the text).

So with 1.) the second word "green" in will not show the green background (bug!) ("cell" is a UITableViewCell with UILabel "label" as a subview):

1.)

text = [[NSMutableAttributedString alloc] initWithString:@"Green is green. (-> Bug)"];
[text addAttribute:NSBackgroundColorAttributeName value:[UIColor greenColor] range:(NSRange){9,5}];
cell.label.attributedText=text

With 2.) and 3.) the backgrounds are displayed correctly:

2.)

text = [[NSMutableAttributedString alloc] initWithString:@"Green is green. (-> Ok)"];
[text addAttribute:NSBackgroundColorAttributeName value:[UIColor greenColor] range:(NSRange){0,5}];
[text addAttribute:NSBackgroundColorAttributeName value:[UIColor greenColor] range:(NSRange){9,5}];
cell.label.attributedText=text

3.)

text = [[NSMutableAttributedString alloc] initWithString:@"Green is green. (-> Ok)"];
[text addAttribute:NSBackgroundColorAttributeName value:[UIColor greenColor] range:(NSRange){0,5}];
cell.label.attributedText=text

Find screenshot and XCode 6 Project here: Screenshot and XCode 6 Project

Seems for me as a bug in iOS 8 - so a report goes to Apple.

回答1:

Try this, first apply an extra NSBackgroundColorAttributeName in whole of the label with a transparent color

text = [[NSMutableAttributedString alloc] initWithString:@"Green is green. (-> Bug)"];
[text addAttribute:NSBackgroundColorAttributeName value:[UIColor clearColor] range:(NSRange){0,text.length}]; //Fix
[text addAttribute:NSBackgroundColorAttributeName value:[UIColor greenColor] range:(NSRange){9,5}];
cell.label.attributedText=text

回答2:

I'm running into similar issues with NSAttributedString and the NSLinkAttributeName attribute in iOS 8. Specifically, a that starts at the beginning of the string (e.g. "www.cnn.com") displays as expected (using drawWithRect:options:context:). However, if we add the link beyond the first character (e.g "text www.cnn.com") the link does not show as blue or underlined, despite the attributes being correct. These strings usually do have attributes which encompass the entire string and that doesn't seem to matter, perhaps because the "whole string" attributes are added after the NSLink attributes. I've tried swapping the order so the links are added after other attributes, but that doesn't fix the issue.

The only workaround that I have figured out so far is to re-attribute the links with an underline, after adding the attributes that apply to the entire string, like this:

        [_attributedDisplayValue enumerateAttribute:NSLinkAttributeName
                                            inRange:displayValueRange
                                            options:0
                                         usingBlock:^(id value, NSRange range, BOOL *stop) {
                                             [_attributedDisplayValue addAttribute:NSUnderlineColorAttributeName
                                                                             value:[UIColor blueColor]
                                                                             range:range];
                                         }];

回答3:

It's no longer an issue (iOS 9.0) - screenshot