(转)iphone 字符串的多样化显示(NSAttributedString)

NSAttributedString可以让我们使一个字符串显示的多样化,但是目前到iOS 5为止,好像对它支持的不是很好,因为显示起来不太方便(至少没有在OS X上方便)。

首先导入CoreText.framework,并在需要使用的文件中导入:

#import<CoreText/CoreText.h>

创建一个NSMutableAttributedString:

NSMutableAttributedString *attriString = [[[NSMutableAttributedString alloc] initWithString:@"this is test!"]   
                                              autorelease];  

非常常规的创建方式,接下来我们给它配置属性:

//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, 2)];  
//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)];  

这样就算是配置好了,但是我们可以发现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。写一个UIView的子类(假设命名为TView),在initWithFrame中把背景色设为透明(self.backgroundColor = [UIColor clearColor]),然后在重写drawRect方法:

-(void)drawRect:(CGRect)rect{  
    [super drawRect:rect];  
      
    CGContextRef ctx = UIGraphicsGetCurrentContext();  
    CGContextConcatCTM(ctx, CGAffineTransformScale(CGAffineTransformMakeTranslation(0, rect.size.height), 1.f, -1.f));  
      
    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);  
}  

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.

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

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

 

//段落  
    //line break  
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  
[attributedString addAttribute:(NSString *)kCTParagraphStyleAttributeName  
                         value:(id)paragraphStyle  
                         range:NSMakeRange(0, attributedString.length)];  

 

-----------------------------------------猥琐的分界线-----------------------------------------

这并不是唯一的方法,还有另一种替代方案:

CATextLayer *textLayer = [CATextLayer layer];  
textLayer.string = getAttributedString();  
textLayer.frame = CGRectMake(0, CGRectGetMaxY(view.frame), 200, 200);  
[self.view.layer addSublayer:textLayer];  

CATextLayer可以直接支持NSAttributedString!

 

<a href="http://download.csdn.net/detail/zhangao0086/4340376">源码地址</a>

 

原文:http://blog.csdn.net/zhangao0086/article/details/7616385

by yytong

 

 

 

 

 

 

 

posted @ 2012-11-15 21:26  iPhone Dev  阅读(3355)  评论(0编辑  收藏  举报