NSMutableAttributedString's attribute NSStrikethroughStyleAttributeName doesn't work correctly in iOS8

问题

I have a mutable attributed string without NSStrikethroughStyleAttributeName attribute like this:

NSMutableAttributedString *str1 = [[NSMutableAttributedString alloc] initWithString:@"aaaa" attributes:@{NSStrikethroughStyleAttributeName:[NSNumber numberWithInteger:NSUnderlineStyleSingle]}];

and another mutable attributed string with NSStrikethroughStyleAttributeName attribute like this:

NSMutableAttributedString *str2 = [[NSMutableAttributedString alloc] initWithString:@"bbbb"];

and a whole string containing two strings above:

NSMutableAttributedString *labelString = [[NSMutableAttributedString alloc] init];
[labelString appendAttributedString:str1];
[labelString appendAttributedString:str2];

when I attach the whole string to a UILabel:

_label.attributedText = labelString;

It both display well in iOS7 and iOS8, like this:

aaaabbbb

But when I exchange their positions:

[labelString appendAttributedString:str2];
[labelString appendAttributedString:str1];

It display correctly in iOS7 but not correctly in iOS8

ios7: bbbbaaaa ios8: bbbbaaaa

It seems that in iOS8, UILabel doesn't render the strikethrough correctly if the first character in the attributed string is not strikethroughed. I think this is a bug in iOS8, is there anyone who encounter the same problem with me?

回答1:

NSMutableAttributedString *str2 = [[NSMutableAttributedString alloc] initWithString:@"bbbb" attributes:@{NSStrikethroughStyleAttributeName:[NSNumber numberWithInteger:NSUnderlineStyleNone]}];

it should help

回答2:

On iOS8.1.1 we have more problems with setting NSMutableAttributedString, like with NSStrikethroughStyleAttributeName.

If your attributes are not changing try this and it will be.

I started reasoning by the UILabel that is spirit to chaneger attributes, so if we assume that the NSStrikethroughStyleAttributeName not initialized the label text so we will need the initialize it .

What I do is initializing mutableAttributedString by a none NSStrikethroughStyleAttributeName and change this attribute to highlight: result is:

 

NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString: myString attributes: @ {NSStrikethroughStyleAttributeName: @ (NSUnderlineStyleNone)}];
             [string addAttributes: @ {NSStrikethroughStyleAttributeName: @ (NSUnderlineStyleSingle)} range: [myString rangeOfString: mySubString]];
[MyLabel setAttributedText: string];

effective result <= iOS8.1.1

回答3:

Fix for the bug in iOS8: Strike Through first letter of the string with clear color and then Strike through the text in which ever range you want.

回答4:

When you are not starting the index from 0, try this:

NSMutableAttributedString *attributedStr = [[NSMutableAttributedString alloc] initWithString:@"Hello"];
[attributedStr addAttributes:@{NSStrikethroughStyleAttributeName : @(NSUnderlineStyleSingle)} range:NSMakeRange(1, str.length)];
[attributedStr addAttributes:@{NSStrikethroughStyleAttributeName : @(NSUnderlineStyleNone)} range:NSMakeRange(0, 1)];

回答5:

When you add NSStrikethroughStyleAttributeName, you should also add NSBaselineOffsetAttributeName, which is set to 0. And in swift, you should use the rawValue of NSUnderlineStyle.

回答6:

I see the same issue and changing NSStrikethroughStyleAttributeName's value to NSUnderlineStyleNone doesn't fix it. Sure seems like iOS 8 bug.

来源：https://stackoverflow.com/questions/25956183/nsmutableattributedstrings-attribute-nsstrikethroughstyleattributename-doesnt