计算 Label高度

NSString * content = @"测试高度";

CGSize _textLabelSize  = [content boundingRectWithSize:CGSizeMake(ScreenWidth-20, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:[UIFont boldSystemFontOfSize:14]} context:nil].size;

枚举要设置两个 NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading 可以解决有时高度不准的问题。