IOS6上label文字空白

//实时清理累计天数

    if (!_totalDaysLabel) {

        _totalDaysLabel = [[UILabelalloc] init];

    }

    [selfgetTotalCleanDays];

    NSInteger totalDays = [[NSUserDefaultsstandardUserDefaults] integerForKey:KEYTOTALCLEANDAYS];

    NSString *totalDaysStr = [NSStringstringWithFormat:@"%d天",totalDays];

    labelsize = [totalDaysStr sizeWithFont:fontconstrainedToSize:size lineBreakMode:GNLineBreakModeWordWrap];

    _totalDaysLabel.frame =CGRectMake(320.0f - (labelsize.width +SHOWINFORMATION_RIGHT), 44, labelsize.width,44);

    _totalDaysLabel.textColor = [UIColorwhiteColor];

    _totalDaysLabel.textAlignment =GNTextAlignmentRight;

    _totalDaysLabel.text = totalDaysStr;

   _totalDaysLabel.backgroundColor = [UIColorclearColor];  //奇怪了 在IOS6的系统上必须加上这句话才行，不然显示的是空白，在IOS7不加也正常

    [_showInformationView addSubview:_totalDaysLabel];