項目中有這樣的需求，要顯示一本書的概述，默認顯示2行，點擊展開按鈕，顯示全部，點擊收回，有顯示2行。

 

開始的時候按鈕事件中，可能寫的是這樣一段代碼：

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];

    }

可以通過setNumberOfLines:0,來讓概述的所以內容顯示出來，但如果，不計算所要顯示全部內容的總高度，label的寬高是不會自動增大的。

 

 

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

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

 

    }