UILabel * testlable = [[UILabel alloc]initWithFrame:CGRectMake(10,20,200,20)];
NSString * tstring =@"UILabel
ios7
与ios7之前实现自适应撑高的方法,文本的内容长度不一，我们需要根据内容的多少来自动换行处理。在IOS7下要求font，与breakmode与之
前设置的完全一致sizeWithFont:font constrainedToSize:size
lineBreakMode:NSLineBreakByCharWrapping";
testlable.numberOfLines =2;
UIFont * tfont = [UIFont systemFontOfSize:14];
testlable.font = tfont;
testlable.lineBreakMode =NSLineBreakByTruncatingTail ;
testlable.text = tstring ;
[testlable setBackgroundColor:[UIColor redColor]];
[self.view addSubview:testlable];
CGSize size =CGSizeMake(300,60);
NSDictionary * tdic = [NSDictionary dictionaryWithObjectsAndKeys:tfont,NSFontAttributeName,nil];
CGSize
actualsize =[tstring boundingRectWithSize:size
options:NSStringDrawingUsesLineFragmentOrigin attributes:tdic
context:nil].size;
testlable.frame =CGRectMake(10,20, actualsize.width, actualsize.height);