uilabel自适应高度

  NSString *str=@"// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the gamehhhhhhhhhhh看见了刚刚好hi了;会考虑换回来来了;了;两节课;绿林豪客;哈伦裤;哈伦裤;哈伦裤;好可怜;哈伦裤;哈伦裤;哈伦裤;哈伦裤;哈伦裤;好可怜;哈伦裤;好vfGfgigfigqiFGIwgggoGOGLFGGFKVMBXZVGHSDFGLAHOFHYAWOYFOAWHOGFAWOYEFOWOFOWHFOAEW可怜;.";
   
    //获取文字的rect
    NSDictionary *dact=@{NSFontAttributeName:[UIFont systemFontOfSize:17]};//17代表字体大小,默认17
    
    //
    CGRect textRect=[str boundingRectWithSize:CGSizeMake(320, 1000) options: NSStringDrawingUsesLineFragmentOrigin attributes:dact context:nil];
    
   //NSLog(@"%@",NSStringFromCGRect(textRect));
    
    
    
    UILabel *label=[[UILabel alloc]init];
    label.frame=CGRectMake(0,22, 320, 20);
    //label.frame.size.height=textRect.size.height;//frame中的值不可以单独修改(不可以这样)
    CGRect tempRect=label.frame;
    //单独修改高之后,再用tempRect给frame赋值
    tempRect.size.height=textRect.size.height;//用上面计算好的高付给需要修改的高
    label.frame=tempRect;
    
    
    
    label.text=str;
    //label.backgroundColor=[UIColor redColor];
    label.numberOfLines=0;
    [self.window addSubview:label];