iOS:何时调用 cellForRowAtIndexPath？还是标签会更新？

Question

我开始迷糊了。我正在为我的 TableView 数据使用 FetchedResultsController。在每个单元格中，我都有一个按钮和一个在 cellForRowAtIndexPath 方法中用 indexPath.Row 标记的文本字段:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //Data model and cell setup
    static NSString *CellIdentifier = @"MainCategoryCell";
    MainCategoryTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
    MainCategory *mainCategory = [self.fetchedResultsController objectAtIndexPath:indexPath];

    /* ... */

    cell.title.tag = indexPath.row;
    cell.iconButton.tag = indexPath.row;

    return cell;
}

现在，对于 Fetched Results Controller ，我的行移动方法有点复杂。但是我很确定标签在移动后不会更新。这是正常的吗？ cellForRow 方法是否仅在创建新单元格后调用？我必须在移动方法中自己更新标签吗？我怎样才能在那里访问单元格中对象的标签属性？

- (void)tableView:(UITableView *)tableView
moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath
      toIndexPath:(NSIndexPath *)destinationIndexPath;
{
    // Process the row move. This means updating the data model to correct the item indices.

    //reordering has been defined in the CoreDataViewController so the
    //FetchedResultsController doesn't mess up the reordering since he would update
    //the fetched results permanently while reordering
    self.reordering = YES;

    //Makes only a mutable copy of the array, but NOT the objects (references) within
    NSMutableArray *fetchedResults = [[self.fetchedResultsController fetchedObjects] mutableCopy];

    // Grab the item we're moving
    NSManagedObject *resultToMove = [self.fetchedResultsController objectAtIndexPath:sourceIndexPath];

    // Remove the object we're moving from the array.
    [fetchedResults removeObject:resultToMove];
    // Now re-insert it at the destination.
    [fetchedResults insertObject:resultToMove atIndex:[destinationIndexPath row]];

    // All of the objects are now in their correct order. Update each
    // object's displayOrder field by iterating through the array.
    int i = 1;
    for (MainCategory *fetchedResult in fetchedResults)
    {
        fetchedResult.position = [NSNumber numberWithInt:i++];
    }

    // Save
    NSError *error = nil;
    [self.budgetDatabase.managedObjectContext save:&error];

    // re-do the fetch so that the underlying cache of objects will be sorted
    // correctly
    [self.fetchedResultsController performFetch:&error];

    self.reordering = NO;
}

Answer 1

是的，移动单元格时标签不会更新是正常的。由于所有单元格都有可能被移动，只需重新加载表格 View 即可让它为您的按钮和文本框重新生成标签。

[tableView reloadData];