1 - (void)setupLabel {
 2     //准备工作
 3     UILabel *textLabel = [[UILabel alloc] init];
 4     textLabel.font = [UIFont systemFontOfSize:16];
 5     NSString *str = @"222222222222222222222222222222222222222222";
 6     textLabel.text = str;
 7     textLabel.backgroundColor = [UIColor redColor];
 8     textLabel.numberOfLines = 0;//根据最大行数需求来设置   
 9     textLabel.lineBreakMode = NSLineBreakByTruncatingTail;
10     CGSize maximumLabelSize = CGSizeMake(100, 9999);//labelsize的最大值
11     //关键语句
12     CGSize expectSize = [textLabel sizeThatFits:maximumLabelSize];
13     //别忘了把frame给回label，如果用xib加了约束的话可以只改一个约束的值
14     textLabel.frame = CGRectMake(20, 70, expectSize.width, expectSize.height);
15     [self.view addSubview:textLabel];
16 }