UILabel首行缩进问题亟待解决

UILabel* contentLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 100, self.view.frame.size.width, 200)];
    contentLabel.backgroundColor = [UIColor redColor];
    contentLabel.numberOfLines = 0;
    [self.view addSubview:contentLabel];
    NSString *_test  =  @"首行缩进根据字体大小自动调整间个据字" ;
    NSMutableParagraphStyle *paraStyle01 = [[NSMutableParagraphStyle alloc] init];
    paraStyle01.alignment = NSTextAlignmentLeft;  //对齐
    paraStyle01.headIndent = 0.0f;//行首缩进
    //参数：（字体大小17号字乘以2，34f即首行空出两个字符）
    CGFloat emptylen = contentLabel.font.pointSize * 10.0;
    paraStyle01.firstLineHeadIndent = emptylen;//首行缩进
    paraStyle01.tailIndent = 0.0f;//行尾缩进
    paraStyle01.lineSpacing = 2.0f;//行间距
    NSAttributedString *attrText = [[NSAttributedString alloc] initWithString:_test attributes:@{NSParagraphStyleAttributeName:paraStyle01}];
    contentLabel.attributedText = attrText;

触发条件：firstLineHeadIndent一定要足够大，文字刚好展示一行多几个字，就会出现如下图，文字显示不全的问题。哪位路过的大神帮忙解决一下哈，谢谢！！！