需求：給UIbutton設置兩行文字，兩行文字字體顏色各不相同。兩行文字均水平居中。

Glass.png

NSMutableAttributedString *title = [[NSMutableAttributedString alloc] initWithString:[NSString stringWithFormat:@"%@\n",@"第一行文字"] attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:20], NSForegroundColorAttributeName:[UIColor blueColor]}];

    NSAttributedString *time = [[NSAttributedString alloc] initWithString:@"第二行" attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:40],NSForegroundColorAttributeName:[UIColor blackColor]}];

    [title appendAttributedString:time];

    NSMutableParagraphStyle *paraStyle = [[NSMutableParagraphStyle alloc] init];
    [paraStyle setLineSpacing:10];
    paraStyle.alignment = NSTextAlignmentCenter;
    [title addAttributes:@{NSParagraphStyleAttributeName:paraStyle} range:NSMakeRange(0, title.length)];

    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(0, 100, 375, 300)];
    btn.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
    [btn setAttributedTitle:title forState:UIControlStateNormal];

NSString *string = @"之二噶山東干嘛干嘛沒代溝按摩棒\n嘎嘎繳納低昂";
    NSArray *array = [string componentsSeparatedByString:@"\n"];

    NSAttributedString * attString = [[NSAttributedString alloc] initWithString:@"耐煩地\n愛國迪迦奧is機動工愛的"];
    NSRange range = [attString.string rangeOfString:@"\n"];
    NSAttributedString *component = [attString attributedSubstringFromRange:NSMakeRange(0, range.location)];

NSString 可以根據(jù)某個特定的字符將string分割開，但是NSAttributedString沒有這個方法（思維誤區(qū)：NSAttributedString并不是繼承自NSString。NSAttributedString有個string屬性，可以獲取到富文本中的字符串）。

屬性字典的屬性名稱全部在NSAttributedString.h類中。