iOS使用NSMutableAttributedString 实现富文本（不同颜色字体、下划线等）

- (id)initWithString:(NSString *)str;
//例：
NSMutableAttributedString *AttributedStr = [[NSMutableAttributedStringalloc]initWithString:@"今天天气不错呀"];

- (id)initWithString:(NSString *)str attributes:(NSDictionary *)attrs;

//字典中存放一些属性名和属性值，如：
NSDictionary *attributeDict = [NSDictionarydictionaryWithObjectsAndKeys:
[UIFontsystemFontOfSize:15.0],NSFontAttributeName,
[UIColorredColor],NSForegroundColorAttributeName,
NSUnderlineStyleAttributeName,NSUnderlineStyleSingle,nil];
NSMutableAttributedString *AttributedStr = [[NSMutableAttributedStringalloc]initWithString:@"今天天气不错呀" attributes:attributeDict];
- (id)initWithAttributedString:(NSAttributedString *)attester;
//使用NSAttributedString初始化，跟NSMutableString，NSString类似

//使用方法：
//为某一范围内文字设置多个属性
- (void)setAttributes:(NSDictionary *)attrs range:(NSRange)range;
//为某一范围内文字添加某个属性
- (void)addAttribute:(NSString *)name value:(id)value range:(NSRange)range;
//为某一范围内文字添加多个属性
- (void)addAttributes:(NSDictionary *)attrs range:(NSRange)range;
//移除某范围内的某个属性
- (void)removeAttribute:(NSString *)name range:(NSRange)range;

NSFontAttributeName
//字体
NSParagraphStyleAttributeName
//段落格式
NSForegroundColorAttributeName
//字体颜色
NSBackgroundColorAttributeName
//背景颜色
NSStrikethroughStyleAttributeName
//删除线格式
NSUnderlineStyleAttributeName
//下划线格式
NSStrokeColorAttributeName
//删除线颜色
NSStrokeWidthAttributeName
//删除线宽度
NSShadowAttributeName
//阴影

UILabel *testLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 100, 320, 30)];

testLabel.backgroundColor = [UIColor lightGrayColor];

testLabel.textAlignment = NSTextAlignmentCenter;

NSMutableAttributedString *AttributedStr = [[NSMutableAttributedString alloc]initWithString:@"今天天气不错呀"];

[AttributedStr addAttribute:NSFontAttributeName

value:[UIFont systemFontOfSize:16.0]

range:NSMakeRange(2, 2)];

[AttributedStr addAttribute:NSForegroundColorAttributeName

value:[UIColor redColor]

range:NSMakeRange(2, 2)];

testLabel.attributedText = AttributedStr;

[self.view addSubview:testLabel];