UILabel的自适应 高度

NSString* text=@"dwqqqqqqqqqqqqqqqqq";

//初始化label
UILabel *comments = [[UILabel alloc] init];
comments.text = text;

//设置自动行数与字符换行

[comments setNumberOfLines:0];
UIFont *font =[UIFont fontWithName:@"Helvetica" size:13];
comments.font = font;

//设置一个行高上限

CGSize constraint = CGSizeMake(280, 20000.0f);
CGSize size = [text sizeWithFont:font constrainedToSize:constraint lineBreakMode:NSLineBreakByCharWrapping];

//计算实际frame大小，并将label的frame变成实际大小

[comments setFrame:CGRectMake(5,indexPath.row==2?5:1, size.width, size.height+12)];
[image addSubview:comments];
[cell.contentView addSubview:comments];

这样就可以实现自动行数和换行了。