时间 2014-03-31 21:18:28  CSDN博客原文  http://blog.csdn.net/u011439689/article/details/22693679

首先导入CoreText.framework，并在需要使用的文件中导入：  
#import<CoreText/CoreText.h>  
新建一个类，继承UILabel，以下为文件内容：

MyLabel.h

//MyLabel.h
#import <Foundation/Foundation.h>
#import <CoreText/CoreText.h>@interface MyLabel : UILabel@end

MyLabel.m

//MyLabel.m
#import "MyLabel.h"@implementation MyLabel//NSAttributedString继承于NSObject，并且不支持任何draw的方法，那我们就只能自己draw了。
-(void)drawRect:(CGRect)rect{[super drawRect:rect];NSAttributedString *attriString = [self getAttributedString];//在代码中我们调整了CTM(current transformation matrix)，这是因为Quartz 2D的坐标系统不同CGContextRef ctx = UIGraphicsGetCurrentContext();CGContextConcatCTM(ctx, CGAffineTransformScale(CGAffineTransformMakeTranslation(0, rect.size.height), 1.f, -1.f));//CTFramesetter是CTFrame的创建工厂，NSAttributedString需要通过CTFrame绘制到界面上，得到CTFramesetter后，创建path（绘制路径），然后得到CTFrame，最后通过CTFrameDraw方法绘制到界面上。CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attriString);CGMutablePathRef path = CGPathCreateMutable();CGPathAddRect(path, NULL, rect);CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);CFRelease(path);CFRelease(framesetter);CTFrameDraw(frame, ctx);CFRelease(frame);/*
  //------------------------------------------------------------------------
  //----------------取消注释，同样可以实现UILabel上展示不同样式的文字--------------
  //------------------------------------------------------------------------
  CATextLayer *textLayer = [CATextLayer layer];
  textLayer.string = [self getAttributedString];
  textLayer.frame = CGRectMake(0, 50, 200, 200);//可调整位置
  textLayer.backgroundColor = [UIColor purpleColor].CGColor;
  [self.layer addSublayer:textLayer];
  */
}-(NSMutableAttributedString *)getAttributedString{//创建一个NSMutableAttributedStringNSMutableAttributedString *attriString = [[[NSMutableAttributedString alloc] initWithString:@"Come on,baby!Come on,baby!Come on,baby!"]autorelease];//把this的字体颜色变为红色[attriString addAttribute:(NSString *)kCTForegroundColorAttributeName
            value:(id)[UIColor redColor].CGColor
            range:NSMakeRange(0, 4)];//把is变为黄色[attriString addAttribute:(NSString *)kCTForegroundColorAttributeName
            value:(id)[UIColor yellowColor].CGColor
            range:NSMakeRange(5, 16)];//改变this的字体，value必须是一个CTFontRef[attriString addAttribute:(NSString *)kCTFontAttributeName
            value:(id)CTFontCreateWithName((CFStringRef)[UIFont boldSystemFontOfSize:14].fontName,14,NULL)
            range:NSMakeRange(0, 4)];//给this加上下划线，value可以在指定的枚举中选择[attriString addAttribute:(NSString *)kCTUnderlineStyleAttributeName
            value:(id)[NSNumber numberWithInt:kCTUnderlineStyleDouble]
            range:NSMakeRange(0, 4)];/*
  换行的实现

  如果想要计算NSAttributedString所要的size，就需要用到这个API：
  CTFramesetterSuggestFrameSizeWithConstraints，用NSString的sizeWithFont算多行时会算不准的，因为在CoreText里，行间距也是你来控制的。
  设置行间距和换行模式都是设置一个属性：kCTParagraphStyleAttributeName，这个属性里面又分为很多子
  属性，其中就包括
  kCTLineBreakByCharWrapping
  kCTParagraphStyleSpecifierLineSpacingAdjustment
  设置如下：*//*
  //-------------取消注释，实现换行-------------

  CTParagraphStyleSetting lineBreakMode;
  CTLineBreakMode lineBreak = kCTLineBreakByCharWrapping; //换行模式
  lineBreakMode.spec = kCTParagraphStyleSpecifierLineBreakMode;
  lineBreakMode.value = &lineBreak;
  lineBreakMode.valueSize = sizeof(CTLineBreakMode);
  //行间距
  CTParagraphStyleSetting LineSpacing;
  CGFloat spacing = 4.0;  //指定间距
  LineSpacing.spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;
  LineSpacing.value = &spacing;
  LineSpacing.valueSize = sizeof(CGFloat);

  CTParagraphStyleSetting settings[] = {lineBreakMode,LineSpacing};
  CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(settings, 2);   //第二个参数为settings的长度
  [attriString addAttribute:(NSString *)kCTParagraphStyleAttributeName
  value:(id)paragraphStyle
  range:NSMakeRange(0, attriString.length)];
  */return attriString;
}@end

测试代码

先要 #import "MyView.h"，在适当位置创建MyLabel的对象，并添加到View中

MyLabel *myLabel = [[MyLabel alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
[self.view addSubview:myLabel];
[myLabel release];

效果图如下：