设置IOS的UILabe l动态高度方法

 　　开始的时候按钮事件中，可能写的是这样一段代码：

　　if (isExpand) {

　　[lblBrief setNumberOfLines:2];

　　lblBrief.text = [StringUtil subString:strBrief AndSubLength:90];

　　[btnBrief setImage:[UIImage imageNamed:@"detailBriefDown"] forState:UIControlStateNormal];

　　[btnBrief setImage:[UIImage imageNamed:@"detailBriefDown"] forState:UIControlStateHighlighted];

　　}else{

　　[lblBrief setNumberOfLines:0];

　　lblBrief.text = strBrief;

　　[btnBrief setImage:[UIImage imageNamed:@"detailBriefUp"] forState:UIControlStateNormal];

　　[btnBrief setImage:[UIImage imageNamed:@"detailBriefUp"] forState:UIControlStateHighlighted];

　　}

　　可以通过setNumberOfLines:0,来让概述的所以内容显示出来，但如果，不计算所要显示全部内容的总高度，label的宽高是不会自动增大的。

　　else{

　　[lblBrief setNumberOfLines:0];

　　lblBrief.text = strBrief;

　　CGSize constraint = CGSizeMake(self.view.frame.size.width - (15 * 2), 20000.0f);

　　CGSize size = [strBrief sizeWithFont:[UIFont systemFontOfSize:10]constrainedToSize:constraint lineBreakMode:UILineBreakModeWordWrap];

　　[brief setFrame:CGRectMake(15,160,size.width,size.height)];

　　[btnBrief setI

　　[btnBrief setImage:[UIImage imageNamed:@"detailBriefUp"]forState:UIControlStateHighlighted];

　　}