Objective c ios7 CATextLayer的字体颜色不会更改

我正在为我的文本使用属性字符串，它在iOS 6和iOS 8中运行良好，但在iOS 7中，我看不到字体颜色的变化。下面是我的几段代码

  CATextLayer *titleLayer = [CATextLayer layer];
            titleLayer.frame = rect;
            titleLayer.alignmentMode = kCAAlignmentCenter;
            titleLayer.truncationMode = kCATruncationEnd;
            titleLayer.string = [self attributedTitleAtIndex:idx];

- (NSAttributedString *)attributedTitleAtIndex:(NSUInteger)index 
{
           UIColor *titleColor=[UIColor redColor];
            UIColor *titleColor1 = titleAttrs[NSForegroundColorAttributeName];

            UIFont *font;
            if (selected) {
                font = CFBridgingRelease(CFBridgingRetain([UIFont fontWithName:@"HelveticaNeue-Bold" size:16.0]));
            }else {
                font = CFBridgingRelease(CFBridgingRetain([UIFont fontWithName:@"HelveticaNeue" size:16.0]));
            }
            NSArray *arrSep = [title componentsSeparatedByString:@"("];
            NSString *strSecondText = [NSString stringWithFormat:@"(%@",[arrSep objectAtIndex:1]];
            NSString *strFrontText = [arrSep objectAtIndex:0];


            NSMutableAttributedString *attString=[[NSMutableAttributedString alloc] initWithString:title];

            [attString addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, [title length])];
            [attString addAttribute:(id)kCTForegroundColorAttributeName value:titleColor1 range:NSMakeRange(0, [title length])];
//            [attString addAttribute:NSForegroundColorAttributeName value:titleColor range:NSMakeRange(strFrontText.length, [strSecondText length])];

            NSRange range1 = [title rangeOfString:strSecondText];


            [attString addAttribute:(id)kCTForegroundColorAttributeName value:[UIColor redColor] range:range1];

//            return [[NSAttributedString alloc] initWithString:(NSString *)title attributes:attString];

            return attString;
}

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检查iOS 7或8是否成功工作

CTFontRef fontFace = CTFontCreateWithName((__bridge CFStringRef)(@"HelfaSemiBold"), 24.0, NULL);
NSString *title=@"Chirag Kalsariya";

NSMutableAttributedString *attString=[[NSMutableAttributedString alloc] initWithString:title ];

[attString addAttribute:(NSString*)kCTFontAttributeName value:(__bridge id)fontFace range:NSMakeRange(0, [title length])];
[attString addAttribute:(NSString*)kCTForegroundColorAttributeName value:(__bridge id)[UIColor blueColor].CGColor range:NSMakeRange(0, 6)];

[attString addAttribute:(NSString*)kCTForegroundColorAttributeName value:(__bridge id)[UIColor blackColor].CGColor range:NSMakeRange(6, 10)];
CATextLayer *titleLayer = [CATextLayer layer];
titleLayer.frame = CGRectMake(0, 0, 300, 100);
titleLayer.alignmentMode = kCAAlignmentCenter;
titleLayer.truncationMode = kCATruncationEnd;
titleLayer.string = attString;

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你好如果除了代码之外，还提供一些简短的解释，这通常会很有帮助。请看@Chirag Kalsariya，我不想贴标签。我想这样设置字符串：titleLayer.string=[self-attributedTitleAtIndex:idx]；