UILabel首行缩进 & 顶部和底部对齐

首行缩进

- (NSAttributedString *)resetContentText:(NSString *)text
{
    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:text];
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.alignment = NSTextAlignmentLeft;
    paragraphStyle.maximumLineHeight = 60;  //最大的行高
    paragraphStyle.lineSpacing = 5;  //行间距
    [paragraphStyle setFirstLineHeadIndent: 24];//首行缩进 根据用户昵称宽度在加5个像素
    [attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0,text.length)];
    return attributedString;
}

//底部和顶部对齐

@interface UILabel (VerticalAlign)
- (void)alignTop;
- (void)alignBottom;
@end

@implementation UILabel (VerticalAlign)

- (void)alignTop {
    CGSize fontSize = [self.text sizeWithFont:self.font];
    double finalHeight = fontSize.height * self.numberOfLines;
    double finalWidth = self.frame.size.width;    //expected width of label
    CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
    int newLinesToPad = (finalHeight  - theStringSize.height) / fontSize.height;
    for(int i=0; i<newLinesToPad; i++)
        self.text = [self.text stringByAppendingString:@"\n "];
}

- (void)alignBottom {
    CGSize fontSize = [self.text sizeWithFont:self.font];
    double finalHeight = fontSize.height * self.numberOfLines;
    double finalWidth = self.frame.size.width;    //expected width of label
    CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
    int newLinesToPad = (finalHeight  - theStringSize.height) / fontSize.height;
    for(int i=0; i<newLinesToPad; i++)
        self.text = [NSString stringWithFormat:@" \n%@",self.text];
}

@end