iphone - uitableview 的最后一行中的值发生变化

Question

我有一个 UITableView，其中每一行都有一个带有浮点值的标签。最后一行的标签应显示总金额。

它显示总金额很好，但如果 tableView 滚动到屏幕外并返回，金额会增加。

 if(tableView == self.allTab)
{
if(indexPath.section == 0)
    {
        self.firstLabel.text = @"Category";
        self.firstLabel.textColor = [UIColor redColor];
        self.secondLabel.text = @"Date";
        self.secondLabel.textColor = [UIColor redColor];
        self.thirdLabel.text = @"Amount";
        self.thirdLabel.textColor = [UIColor redColor];
    }  

else if(indexPath.section == 1)
    {
        NSManagedObject *records = nil;
        records = [self.listOfExpenses objectAtIndex:indexPath.row];
        self.firstLabel.text = [records valueForKey:@"category"];
        NSString *dateString = [NSString stringWithFormat:@"%@",[records valueForKey:@"date"]];
        NSString *dateWithInitialFormat = dateString;
        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
        [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss Z"];
        NSDate *date = [dateFormatter dateFromString:dateWithInitialFormat];
        [dateFormatter setDateStyle:NSDateFormatterMediumStyle];
        NSString *dateWithNewFormat = [dateFormatter stringFromDate:date];
        self.secondLabel.text = dateWithNewFormat;
        NSString *amountString = [NSString stringWithFormat:@"%@",[records valueForKey:@"amount"]];
        self.thirdLabel.text = amountString;
        totalAmount = totalAmount + [amountString doubleValue];
    }

else if(indexPath.section == 2)
{
        self.firstLabel.text = @"Total";
        self.firstLabel.textColor = [UIColor redColor];
        self.thirdLabel.text = [NSString stringWithFormat:@"%.2f",totalAmount];
        self.thirdLabel.textColor = [UIColor redColor];
        self.thirdLabel.adjustsFontSizeToFitWidth = YES;
}
}

Answer 1

您不应该在 cellForRowAtIndexPath 中计算总计，因为当它再次滚动时它会再次计算总计，因此请使用其他方法计算总计，如下所示:

-(float)calculateTotal
{
    totalAmount = 0;
   for(int i =0;i<[self.listOfExpenses length];i++)
   {
      NSManagedObject *records = nil;
        records = [self.listOfExpenses objectAtIndex:i];
      NSString *amountString = [NSString stringWithFormat:@"%@",[records valueForKey:@"amount"]];
      totalAmount = totalAmount + [amountString doubleValue];
   }

 return totalAmount;
} 

并按如下方式赋值:

 self.thirdLabel.text = [NSString stringWithFormat:@"%.2f",[self calculateTotal]];