UILabel实现文本自适应方法

- ( void )initUserInterface
{
    UILabel *label = [[UILabel alloc]init];
    label.numberOfLines = 0 ; // 需要把显示行数设置成无限制
    label.font = [UIFont systemFontOfSize: 15 ];
    label.textAlignment = NSTextAlignmentCenter;
    label.text = @ "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" ;
    CGSize size =  [self sizeWithString:label.text font:label.font];
    label.bounds = CGRectMake( 0 , 0 , size.width, size.height);
    label.center = self.view.center;
    [self.view addSubview:label];

}
// 定义成方法方便多个label调用 增加代码的复用性
- (CGSize)sizeWithString:(NSString *)string font:(UIFont *)font
{
    CGRect rect = [string boundingRectWithSize:CGSizeMake( 320 , 8000 ) //限制最大的宽度和高度
                                       options:NSStringDrawingTruncatesLastVisibleLine | NSStringDrawingUsesFontLeading  |NSStringDrawingUsesLineFragmentOrigin //采用换行模式
                                    attributes:@{NSFontAttributeName: font} //传人的字体字典
                                       context:nil];

    return rect.size;
}