iOS 动态计算文本高度

富文本计算方法

// 富文本格式
    NSMutableParagraphStyle *paraStyle = [[NSMutableParagraphStyle alloc] init];
    paraStyle.lineBreakMode = NSLineBreakByCharWrapping;
    paraStyle.lineSpacing = 1.0;

    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithData:[introduceText dataUsingEncoding:NSUnicodeStringEncoding] options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType } documentAttributes:nil error:nil];
    [attributedString setAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:14*KWIDTH_IPHONE6_SCALE], NSParagraphStyleAttributeName:paraStyle}  range:NSMakeRange(0, attributedString.length)];
    [attributedString addAttribute:NSBaselineOffsetAttributeName value:[NSNumber numberWithFloat:5.0] range:NSMakeRange(0, attributedString.length)];

//富文本高度计算方法
    CGSize lblSize = [attributedString boundingRectWithSize:CGSizeMake(labelSize, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin context:nil].size;
    double describeheight = ceil(lblSize.height )  ;//为防止文字显示不全，采用向上取整函数获取最终文本高度

普通文本计算方法

    CGSize lblSize = [model.describestring boundingRectWithSize:CGSizeMake(SCREEN_WIDTH-44, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:14*KWIDTH_IPHONE6_SCALE]} context:nil].size;
    double describeheight = ceil(lblSize.height )  ;

HTML文本若用普通文本计算高度的方法（第二种方法）计算，会导致计算高度偏小，文本显示不全