UITableView 数据源必须从 tableView 返回单元格：cellForRowAtIndexPath

Question

我在ViewController 中添加的搜索栏有问题。

我收到以下错误：

Assertion failure in -[UISearchResultsTableView _configureCellForDisplay:forIndexPath:], /SourceCache/UIKit/UIKit-2935.137/UITableView.m:6509
2014-04-03 18:08:24.355 MyFood[6405:60b] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:'

configureCell:

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {        
    //    ToDos *toDo = [self.fetchedResultsController objectAtIndexPath:indexPath];
    if (viewMode==AlphabeticalOrder) {
        Inventory *toDo=nil;
        if (self.searchDisplayController.isActive) {
            toDo = [searchResults objectAtIndex:indexPath.row];
        } else {
            toDo=[inventoryProducts objectAtIndex:indexPath.row];
        }
        cell.textLabel.text = toDo.inventoryProductName;
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterShortStyle];
        NSDate *dt = toDo.expireDate;
        NSString *dateAsString = [formatter stringFromDate:dt];
        cell.detailTextLabel.text = [NSString stringWithFormat:@"Until: %@", dateAsString];
    } else {
        Inventory *toDo=nil;
        if (self.searchDisplayController.isActive) {
            NSDictionary *sectionDict=[searchResults objectAtIndex:indexPath.section];
            NSArray *sectionData=[sectionDict objectForKey:@"SECTION_DATA"];
            toDo = [sectionData objectAtIndex:indexPath.row];
        } else {
            NSDictionary *sectionDict=[inventoryProducts objectAtIndex:indexPath.section];
            NSArray *sectionData=[sectionDict objectForKey:@"SECTION_DATA"];
            toDo=[sectionData objectAtIndex:indexPath.row];
        }
        cell.textLabel.text = toDo.inventoryProductName;
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterShortStyle];
        NSDate *dt = toDo.expireDate;
        NSString *dateAsString = [formatter stringFromDate:dt];
        cell.detailTextLabel.text = [NSString stringWithFormat:@"Until: %@", dateAsString];
    }
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    // Configure the cell.
    [self configureCell:cell atIndexPath:indexPath];
    return cell;

}

代码搜索栏：

   - (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
    {
        if (searchText.length!=0) {
            if (viewMode==AlphabeticalOrder) {
                NSPredicate *resultPredicate = [NSPredicate predicateWithFormat:@"name contains[c] %@", searchText];
                //            [searchResults removeAllObjects];
                //            [searchResults addObjectsFromArray:[inventoryProducts filteredArrayUsingPredicate:resultPredicate]];
                searchResults=[inventoryProducts filteredArrayUsingPredicate:resultPredicate];
            } else {
                //-section mode
                NSMutableArray *newDataArray=[NSMutableArray array];
                for (NSMutableDictionary *aSectionDict in inventoryProducts) {
                    NSArray *sectionData=(NSArray*)[aSectionDict objectForKey:@"SECTION_DATA"];
                    NSPredicate *resultPredicate = [NSPredicate predicateWithFormat:@"name contains[c] %@", searchText];
                    NSArray *filteredArray=[sectionData filteredArrayUsingPredicate:resultPredicate];
                    NSDictionary *sectionDataModified=[NSDictionary dictionaryWithObjectsAndKeys:filteredArray,@"SECTION_DATA",[aSectionDict objectForKey:@"SECTION_TITLE"],@"SECTION_TITLE", nil];
                    [newDataArray addObject:sectionDataModified];
                }
                searchResults=[NSArray arrayWithArray:newDataArray];
            }
        }
    }

    -(BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
    {
        [self filterContentForSearchText:searchString
                                   scope:[[self.searchDisplayController.searchBar scopeButtonTitles]
                                          objectAtIndex:[self.searchDisplayController.searchBar
                                                         selectedScopeButtonIndex]]];

        return YES;
    }

谁能帮忙？

Answer 1

由于添加了搜索栏，需要检查单元格是否为nil：

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

 // This is added for a Search Bar - otherwise it will crash due to
//'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:'
if (!cell) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}

   // Configure the cell.
    [self configureCell:cell atIndexPath:indexPath];
    return cell;

}

Answer 2

当您使用 UISearchDisplayController 时，结果会显示在一个单独的 UITableView 中，该 UITableView 使用您的原始视图控制器作为委托和数据源。由于该 UITableView 未在您的故事板中设置（它是动态创建和加载的），因此它无法访问您的原型单元格。通过使用，我能够获得一个类似的示例：

UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];

我有点担心，因为您要求一个表格视图创建要在不同表格视图中使用的单元格。

似乎更好的方法是不要将您的单元格创建为原型单元格，而是在一个单独的 nib 文件中创建它们并从中加载它们。

您还应该阅读UISearchDisplayController 的文档，因为数据源和委托协议的其他一些细节需要更新以反映存在多个表视图在运行的事实。

Answer 3

这告诉您您的方法：cellForRowAtIndexPath 正在返回一个为零的单元格。这会产生此错误。

这里的这一行：UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

将是 nill，因为您从不为单元分配任何内容，也不对它做任何事情。