我的自定义 UITableViewCell(用故事板创建)中的对象为零 [英] Objects inside my custom UITableViewCell (created with storyboard) are nil

问题描述

我通过以下步骤在我的 iPhone 应用程序中创建了一个自定义表格视图单元格.

I've created a custom table view cell in my iPhone app through the following steps.

1. 在我的故事板中，我创建了一个示例单元格，拖入一个 UILabel 和一个 UIImageView.
2. 添加了新文件，我将其创建为 UITableViewCell 的子类.
3. 在 Interface Builder 中，我选择了我的单元格，并将它的类指定为我刚刚在步骤 2 中创建的类.
4. 在我的自定义表格视图单元格的代码中，我创建了两个 IBOutlet 属性并将它们连接到故事板中的 UILabel 和 UIImageView.

5. 我的自定义表格视图单元格还包括一个方法，它接收另一个对象，从中设置自己的属性:

1. In my storyboard, I created a sample cell, dragged in a UILabel and a UIImageView.
2. Added new files, which I made a subclass of UITableViewCell.
3. In Interface Builder, I selected my cell and I assigned its class as the class I just created in step 2.
4. In the code for my custom table view cell, I created two IBOutlet properties and connected them to my UILabel and UIImageView in the storyboard.

5. My custom table view cell also includes a method, where it receives another object from which it sets its own attributes:

-(void)populateWithItem:(PLEItem *)item
{
    if (item.state == PLEPendingItem) {
        status.text = @"Pending upload..."; //status is a UILabel IBOutlet property
    }
    else if(item.state == PLEUploadingItem)
    {
        status.text = @"Uploading...";
    }

    imageView.image = [UIImage imageWithContentsOfFile:item.path]; //imageView is the UIImageView IBOutlet property
}

这个方法是从我的 tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 调用的，如下:

    PLEPendingItemCell* cell = (PLEPendingItemCell*)[tableView dequeueReusableCellWithIdentifier:item_id];
    if (cell == nil) {
        cell = [[PLEPendingItemCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:pending_id];
    }

    [cell populateWithItem:((PLEItem*)[itemList objectAtIndex:indexPath.row])];

    return cell;

问题是单元格总是显示为空.我在 populateWithItem 中设置了一个断点，并意识到该方法中的状态 UILabel 和图像 UIImageView 都为零.

The problem is that the cells always show up empty. I set a breakpoint in populateWithItem and realized that both the status UILabel and the image UIImageView were nil inside that method.

IB 不应该初始化这些吗?如果没有，我应该在哪里做?

Shouldn't IB be initializing these? If not, where should I be doing that?

推荐答案

如果您要在故事板中设置单元格，则始终需要使用 tableView:dequeueReusableCellWithIdentifier:forIndexPath: 创建单元格因为那是故事板创建您的单元格并连接视图的地方.

If you're setting up your cell in the storyboard, you always need to create your cell using tableView:dequeueReusableCellWithIdentifier:forIndexPath: because that's where the storyboard creates your cell and hooks up the views.

直接使用其构造函数创建单元格，就像在您的示例代码中一样，不会从故事板、笔尖等加载任何子视图.您创建的类对故事板原型单元格一无所知.

Creating a cell with its constructor directly, as in your sample code, won't load any subviews from a storyboard, nib, etc. The class you've made doesn't know anything about the storyboard prototype cells.

这篇关于我的自定义 UITableViewCell(用故事板创建)中的对象为零的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！