ios - scrollToItemAtIndexPath 导致应用程序崩溃

Question

我正在尝试通过代码将我的 UICollectionView 滚动到顶部。我正在调用这个方法:

        [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UICollectionViewScrollPositionTop animated:NO];

崩溃:

** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'the collection view's data source did not return a valid cell from -collectionView:cellForItemAtIndexPath: for index path {length = 2, path = 0 - 0}'

不太确定如何解决这个问题？

谢谢!

编辑

这是我的 Collection View 方法 - 如果满足条件，我将加载三种不同类型的单元格:

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath

{   static NSString *tableCellIdentifier = @"TableItemCell";
    static NSString *gridCellIdentifier = @"GridItemCell";
    UIActivityIndicatorView * activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

    if (indexPath.item < [self.tradeSearchArray count]){

        if (self.gridLayoutActive == NO){

            self.switchToTableLayout = NO;
            BBItemTableViewCell *tableItemCell = [collectionView dequeueReusableCellWithReuseIdentifier:tableCellIdentifier forIndexPath:indexPath];

            if ([self.tradeSearchArray count] > 0){

                self.toolBarButtomItem.title = [NSString stringWithFormat:@"%d Results", self.searchResult.searchResults];

                self.switchToTableLayout = NO;

                tableItemCell.gridView = NO;
                tableItemCell.backgroundColor = [UIColor whiteColor];
                tableItemCell.item = self.tradeSearchArray[indexPath.row];

            }
            return tableItemCell;
        }else

        {

            BBItemTableViewCell *gridItemCell= [collectionView dequeueReusableCellWithReuseIdentifier:gridCellIdentifier forIndexPath:indexPath];

            if ([self.tradeSearchArray count] > 0){

                self.toolBarButtomItem.title = [NSString stringWithFormat:@"%d Results", self.searchResult.searchResults];
                self.switchToTableLayout = YES;

                gridItemCell.gridView = YES;
                gridItemCell.backgroundColor = [UIColor whiteColor];
                gridItemCell.item = self.tradeSearchArray[indexPath.row];

            }

            return gridItemCell;
        }
    }else
    {

        BBLoaderCell *loaderCell = [collectionView dequeueReusableCellWithReuseIdentifier:@"LoaderCell" forIndexPath:indexPath];
        loaderCell.backgroundColor = [UIColor clearColor];


    if (self.maximumOffset - self.currentOffset <= 1000.0) {
        [self loadMoreSearchResults];

        if (self.loadingMore){
            dispatch_async(dispatch_get_main_queue(), ^{
                activityIndicator.hidden = NO;
                [loaderCell.spinner startAnimating];
            });
        }
        else{
            dispatch_async(dispatch_get_main_queue(), ^{
                activityIndicator.hidden = YES;
                [loaderCell.spinner stopAnimating];
            });
        }

        return loaderCell;
    }
}

    return nil;

}

Answer 1

问题是线路

return loaderCell;

在if语句中

if (self.maximumOffset - self.currentOffset <= 1000.0)

因此，有时该方法本应返回 loaderCell，但会返回 nil。