1.CATextLayer
为什么要存在CATextLayer呢？它的意义是什么？我们可以用UILabel来写文字，但两者不是一码事，CATextLayer的渲染速度比UILabel快的多，而UILabel的精髓就是用图层代理把字符串用Core Graphics写入如层，CATextLayer则不用，它以涂层的形式几乎包含了UILabel所有的特性，并有额外的新特性。
//create a text layer CATextLayer *textLayer = [CATextLayer layer]; textLayer.frame = self.labelView.bounds; [self.labelView.layer addSublayer:textLayer]; //set text attributes textLayer.foregroundColor = [UIColor blackColor].CGColor; textLayer.alignmentMode = kCAAlignmentJustified; textLayer.wrapped = YES; //choose a font UIFont *font = [UIFont systemFontOfSize:15]; //set layer font CFStringRef fontName = (__bridge CFStringRef)font.fontName; CGFontRef fontRef = CGFontCreateWithFontName(fontName); textLayer.font = fontRef; textLayer.fontSize = font.pointSize; CGFontRelease(fontRef); //choose some text NSString *text = @"Lorem ipsum dolor sit amet, consectetur adipiscing \ elit.Lorem ipsum dolor sit amet, consectetur adipiscing \ elit.Lorem ipsum dolor sit amet, consectetur adipiscing \ elit.Lorem ipsum dolor sit amet, consectetur adipiscing \ elit.Lorem ipsum dolor sit amet, consectetur adipiscing \ elit."; textLayer.string = text; //单写上面的会发现文字显示像素不高，那是因为没有支持retain显示屏，前面说过，要支持retain，需要设置contentsScale textLayer.contentsScale = [UIScreen mainScreen].scale;
2.富文本
这是一个在编程中经常用到的东西,使用富文本需要添加库 #import
//create a text layer CATextLayer *textLayer = [CATextLayer layer]; textLayer.frame = self.labelView.bounds; textLayer.contentsScale = [UIScreen mainScreen].scale; [self.labelView.layer addSublayer:textLayer]; //set text attributes textLayer.alignmentMode = kCAAlignmentJustified; textLayer.wrapped = YES; //choose a font UIFont *font = [UIFont systemFontOfSize:15]; //choose some text NSString *text = @"Lorem ipsum dolor sit amet, consectetur adipiscing \ elit. Quisque massa arcu, eLorem ipsum dolor sit amet, consectetur adipiscing \ elit. Quisque massa arcu, eLorem ipsum dolor sit amet, consectetur adipiscing \ elit. Quisque massa arcu, eLorem ipsum dolor sit amet, consectetur adipiscing \ elit. Quisque massa arcu, e"; //create attributed string NSMutableAttributedString *string = nil; string = [[NSMutableAttributedString alloc] initWithString:text]; //convert UIFont to a CTFont CFStringRef fontName = (__bridge CFStringRef)font.fontName; CGFloat fontSize = font.pointSize; CTFontRef fontRef = CTFontCreateWithName(fontName, fontSize, NULL); //set text attributes NSDictionary *attribs = @{ (__bridge id)kCTForegroundColorAttributeName:(__bridge id)[UIColor blackColor].CGColor, (__bridge id)kCTFontAttributeName: (__bridge id)fontRef }; [string setAttributes:attribs range:NSMakeRange(0, [text length])]; attribs = @{ (__bridge id)kCTForegroundColorAttributeName: (__bridge id)[UIColor redColor].CGColor, (__bridge id)kCTUnderlineStyleAttributeName: @(kCTUnderlineStyleSingle), (__bridge id)kCTFontAttributeName: (__bridge id)fontRef }; [string setAttributes:attribs range:NSMakeRange(6, 5)]; //release the CTFont we created earlier CFRelease(fontRef); //set layer text textLayer.string = string;
