关于UITextView字符串的问题

根据设置的字符串字体大小，计算字符串的高度，目前计算出来的高度是一行的高度，但是显示的却是2行的高度，这是什么原因？

 textview = [[UITextView alloc] init];
    [textview setFrame:CGRectMake(5, 20, 310, 450)];
    textview.font = [UIFont systemFontOfSize:20];
    textview.editable = NO;
    textview.scrollEnabled = YES;


    NSString *text = @"        在现代酒已经融入了人们日常";
    CGSize labelSize1;
    labelSize1 = [text sizeWithFont:[UIFont systemFontOfSize:20]
                 constrainedToSize:CGSizeMake(310, CGFLOAT_MAX)
                     lineBreakMode:NSLineBreakByCharWrapping];

    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:text];
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
    paragraphStyle.lineSpacing = 5;    //行间距
    [attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, text.length)];
    [attributedString addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:20] range:NSMakeRange(0, text.length)];
    textview.attributedText = attributedString;
    [self.view addSubview:textview];

因为你计算高度的时候没有用NSMutableAttributedString