iOS动态调整UILabel高度的几种方法

/**
 * 获取特定格式的属性字符串
 *
 * @param string 原字符串
 * @param font 字体
 * @param spacing 行间距
 *
 * @return 特定格式的属性字符串
 */
- (NSAttributedString *)attributedStringWithString: (NSString *)string andFont: (UIFont *)font andLineSpacing:(CGFloat)spacing
{
 NSMutableAttributedString *contentString = [[NSMutableAttributedString alloc] initWithString:string];
 [contentString addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, contentString.length)];
 NSMutableParagraphStyle * paragraphStyle = [[NSMutableParagraphStyle alloc] init];
 [paragraphStyle setAlignment:NSTextAlignmentLeft];
 [paragraphStyle setLineSpacing:spacing];
 [contentString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [contentString length])]; 
 return [contentString copy];
}

/**
 * 获取根据特定格式的属性字符串计算的新高度
 *
 * @param string  特定格式的属性字符串
 * @param maxWidth UILable的最宽宽度（换行点）
 *
 * @return 根据特定格式的属性字符串计算的新高度
 */
- (CGSize)sizeOfAttributedString: (NSAttributedString *)string withMaxWidth: (CGFloat)maxWidth
{
  CGRect rect = [string boundingRectWithSize:CGSizeMake(maxWidth, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil];
  return rect.size;
}

NSAttributedString *string = [self attributedStringWithString:self.contentString andFont:[UIFont systemFontOfSize:15.0] andLineSpacing:2.0];
CGSize size = [self sizeOfAttributedString:string withMaxWidth:maxWidth];
self.resizeLabel.frame = CGRectMake((self.view.bounds.size.width - maxWidth)/2, 400, maxWidth, size.height);
self.resizeLabel.attributedText = string;

self.orignalLabel.attributedText = [self attributedStringWithString:self.contentString andFont:[UIFont systemFontOfSize:15.0] andLineSpacing:2.0 ];