NSAttributedString change color at end of string

问题

This must be an easy thing to do, but I cannot figure it out.

I have a NSMutableAttributedString that has, for example, "This is a test" in it. I want to color the word "test" blue, which I do with this:

NSMutableAttributedString *coloredText = [[NSMutableAttributedString alloc] initWithString:@"This is a test"];

[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(10,4)];

That works just fine. But now I want to set the text color back to black for anything typed after "test".

If I do:

[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(coloredText.string.length, 1)];

I get an objectAtIndex:effectiveRange: out of bounds error. Assumedly because the range extends beyond the length of the string.

If I do:

[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(coloredText.string.length, 0)];

The error goes away but typing after the word "test" remains blue.

How do I set the current color at the insertion point when it is at the end of the string??

Cheers for any input.

回答1:

You need to recalculate the attributes if the text changes, because their effective range doesn't automatically change with the length of text.

回答2:

In case someone else stumbles upon this, I wanted to post the code I used to solve the problem. I ended up using Kamil's suggestion and adding:

NSAttributedString *selectedString = [textView.attributedText attributedSubstringFromRange:NSMakeRange(textView.attributedText.string.length - 1, 1)];
    __block BOOL isBlue = NO;

    [selectedString enumerateAttributesInRange:NSMakeRange(0, [selectedString length]) options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:^(NSDictionary *attributes, NSRange range, BOOL *stop) {
        isBlue = [[attributes objectForKey:NSForegroundColorAttributeName] isEqual:[UIColor blueColor]];
    }];

    if (isBlue) {
        NSMutableAttributedString *coloredText = [[NSMutableAttributedString alloc] initWithAttributedString:textView.attributedText];
        [coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(textView.attributedText.string.length - 1, 1)];
        textView.attributedText = coloredText;
    }

to the text changed handler.

来源：https://stackoverflow.com/questions/19123503/nsattributedstring-change-color-at-end-of-string

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ios

colors

nsattributedstring