在动态表中重新加载 TableViewCell 的 UILabels [英] Reload TableViewCell's UILabels in dynamic table

问题描述

我得到了带有 UITableView 的应用程序.

I got app with UITableView.

每个 UITableViewCell 中都有 UILabel.我以这种方式添加标签:

There is UILabel in each UITableViewCell. I add labels in this way:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
  //look at the upd
}

但是当我尝试使用其他一些信息重新加载此表中的数据时，旧信息(旧标签)不会消失，但仍在单元格上.

But when i try to reload data in this table with some other information, old infromation (old labels) dont disappear, but still on cells.

看起来像这样:...

我应该如何组织添加 UILabels?

How should i organized adding UILabels?

更新

我以这种方式更正代码:

I correct code in this way:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Recent Dream";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];

        UILabel *textLabel = [[UILabel alloc] init];
        textLabel.frame = CGRectMake(10, 0, self.view.frame.size.width -110, 48);
        textLabel.backgroundColor = [UIColor clearColor];
        textLabel.font = [UIFont boldSystemFontOfSize:16];
        [textLabel setTag:(int)indexPath];
        [cell.contentView addSubview:textLabel];


    }
    // Configure the cell...

    Dream *tempDream = [self.dreams objectAtIndex:indexPath.row];

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"MM/dd/yyyy"];

    //Optionally for time zone converstions
    [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"..."]];

    NSString *stringFromDate = [formatter stringFromDate:tempDream.dateAdd];

    UIColor *background = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:@"bodyWrapper.png"]];

    cell.contentView.backgroundColor = background;

    UILabel *textLabel = (UILabel *)[cell viewWithTag:(int)indexPath];
    textLabel.text = tempDream.title;

    NSLog(@"%@",tempDream.title);
    NSLog(@"%@",textLabel.text);

    cell.textLabel.text = @"";
    cell.detailTextLabel.text = stringFromDate;

    return cell;
}

输出如下所示:

2012-02-20 15:58:10.512 DreamerIOS[3037:10403] lllooooonggg dreeeeeeeaaaaammmm yeeeeeeah
2012-02-20 15:58:10.513 DreamerIOS[3037:10403] (null)
2012-02-20 15:58:10.516 DreamerIOS[3037:10403] dream to end
2012-02-20 15:58:10.516 DreamerIOS[3037:10403] (null)
2012-02-20 15:58:10.519 DreamerIOS[3037:10403] adsfhadskgh dfagfadkuy gadyv dsfdfad fsdf a ghfncdhg hjfg f dfj ghf 
2012-02-20 15:58:10.519 DreamerIOS[3037:10403] (null)

所以，NSLog(@"%@",tempDream.title);没问题，但是 NSLog(@"%@",textLabel.text);一片空白.为什么?

So, NSLog(@"%@",tempDream.title); is OK, but NSLog(@"%@",textLabel.text); is null. Why?

推荐答案

这是因为每次给单元格添加一个新标签.

It is because each time you add a new label to the cell.

当您初始化一个新单元格时，您添加标签并为其设置标签

When you init a new cell, you add the label and set a tag to it

if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];

    //  add label here
    ...
    [label setTag:999];
}

然后在配置cell的时候，使用[UIView viewWithTag:]来获取label的引用

Then when you configure the cell, use [UIView viewWithTag:] to get the reference of the label

UILabel *label = (UILabel *)[cell.contentView viewWithTag:999];

更新:

您应该为标签使用常量值.如果使用 indexPath 作为标签，则可能找不到视图.由于您正在重复使用单元格，系统只会创建一定数量的单元格.当单元格不在视图中(不可见)时，dequeueReusableCellWithIdentifier 将为您获取单元格而不是创建新单元格.

You should use a constant value for the tag. If you use the indexPath as the tag, the view may not found. Since you are reusing the cell, the system only create a certain number of cells. When the cell is out of view (not visible), dequeueReusableCellWithIdentifier will get the cell for you rather than create a new cell.

reusableCell 是您之前创建的视图.您为标签使用动态值的情况将如下所示:您在单元格 10(indexPath) 处，系统找到在 3(indexPath) 处创建的 reusableCell.因为它是在3创建的，所以label标签是3.但是你找到一个带有标签10的视图，因此结果为空.

The reusableCell is a view that you create before. The case you use a dynamic value for the tag will like this: You are at cell 10(indexPath), the system find a reusableCell which is created at 3(indexPath). Since it was created at 3, the label tag is 3. But you find a view with tag 10, therefore the result is null.

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