UITableView由于某种原因正在加载相同的单元格 [英] UITableView is loading the same cells of some reason

问题描述

我有一个TableView加载自定义单元并从服务器上的JSON字符串加载数据.JSON字符串被解析为包含14个ID(id_array)的数组.

I have a TableView loading a custom cell and loading the data from a JSON string on a server. The JSON string is parsed to an array of 14 IDs (id_array).

如果 cell == nil ，那么我正在使用 [id_array objectAtIndex:indexPath.row] 获取ID并从中获取有关该行的更多信息服务器，并设置单元格的标签和图像.

If cell==nil, then I'm using [id_array objectAtIndex:indexPath.row] to get an ID and fetch some more info about for that row from a server, and set up the cell's labels and image.

运行应用程序时，UITableView会加载可见行[0,1,2,3,4](单元格高度为70像素).向下滚动TableView时，将加载行[5]并从服务器获取数据，但是问题在于，超出这一点-TableView将重复这6行，而不是从服务器为新行请求新数据...

When running the app, the UITableView is loading the visible rows [0,1,2,3,4] (cell height is 70px). When scrolling down the TableView, row [5] is loaded and fetching data from the server, but the problem is that beyond that point - the TableView is repeating those 6 rows instead of requesting new data from the server for the new rows...

但是它确实请求第[5]行的新数据，该数据在应用程序首次运行时不可见(且未加载).

But it does request new data for row [5], which is not visible (and not loaded) when the app first runs.

任何人都知道为什么会这样吗?谢谢！

Anyone have any idea why is this happening? Thanks!

这是我的cellForRowAtIndexPath方法

Here is my cellForRowAtIndexPath method

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{       
    static NSString *CellIdentifier = @"CustomCell";
    CustomCell *cell = (CustomCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil) {
        NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"CustomCell" owner:self options:nil];

        for (id currentObject in topLevelObjects) {
            if ([currentObject isKindOfClass:[UITableViewCell class]]) {
                cell = (CustomCell *)currentObject;

                NSString *appsURL = [NSString stringWithFormat:@"http://myAPI.com?id=%@",[app_ids objectAtIndex:indexPath.row]];
                NSLog(@"row -> %d | id -> %@",indexPath.row,[app_ids objectAtIndex:indexPath.row]);
                NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:appsURL]];
                [cell updateAppInfoForCellWithRequest:request];

                break;
            }
        }
    }

    // Configure the cell...

    return cell;
}

推荐答案

如果仅当 cell == nil 时才设置数据，那么这就是您的问题.UITable构建了一个表格视图单元格的缓存，如果单元格为nil，则仅创建一个新的缓存.因此，每次必须设置数据，即在 cell == nil 块之外.

If you are setting data only if cell==nil, then that is your issue. UITable builds a cache of table view cells, only creating a new one if cell is nil. Therefore, you must set your data each time, i.e. outside of the cell==nil block.

以下示例显示了该过程.首先，从池中获取一个单元，如果没有可用单元，则创建一个新单元.为相应的行设置单元格的值.

The example below shows that process. First, grab a cell from the pool, if there isn't a free cell, create a new one. Set the cell's values for the appropriate row.

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

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }

    id someData = [id_array objectAtIndex:indexPath.row]

    cell.textLabel.text = [someData someString];

    return cell;
}

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