iOS 7：insertItemsAtIndexPaths：滾動UICollectionView

Question

我正在開發一個應用程序，其中有無限滾動的圖像UICollectionView。當用戶到達頁面的底部時，我查詢圖像的下一頁，獲取新的indexPaths，並將它們添加到帶有[collectionView insertItemsAtIndexPaths:newIndexPaths]的UICollectionView。

這完全適用於iOS 6.在iOS 7中它可以工作，但它每次都會將用戶滾動回到collectionView的頂部。我試過用reloadData來代替，同樣的事情發生。

任何想法如何我可以防止這種滾動？

UPDATE：包括我的代碼

我有一個顯示在馬賽克圖案圖像的縮略圖（每個圖像的大小不同，所以我用RFQuiltLayout此一UICollectionView我不認爲。這與滾動問題有關，因爲源代碼似乎並不涉及滾動。

我從我們的Parse後端加載每組12個圖像，代碼如下（如果isRefresh爲真，我清除取出圖像陣列並再次加載第一頁）：

- (void)loadImagesStartingAtNum:(int)num withRefresh:(BOOL)isRefresh { 
    NSLog(@"Starting query..."); 

    [PFCloud callFunctionInBackground:@"homeFeed" withParameters:@{@"startNum": [NSNumber numberWithInt:num]} block:^(id objects, NSError *error) { 

     if(!error) { 

      //NSLog(@"Got back home feed objects: %@", objects); 

      NSMutableArray *newIndexPaths = [[NSMutableArray alloc] init]; 

      if (isRefresh) { 
       [imagesArray removeAllObjects]; 
       [imageURLsArray removeAllObjects]; 

       page = 0; 

       for (PFObject *object in objects) { 
        [imagesArray addObject:object]; 
        [imageURLsArray addObject:[XSUtilities urlForImageObject:object]]; 

        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:([imagesArray count] - 1) inSection:0]; 
        NSLog(@"New row: %d", indexPath.row); 
        [newIndexPaths addObject:indexPath]; 
       } 

       if ([newIndexPaths count] > 0) { 
        [feed reloadData]; 
        [refreshControl endRefreshing]; 

        page += 1; 
       } 
      } else { 
       for (PFObject *object in objects) { 
        [imagesArray addObject:object]; 
        [imageURLsArray addObject:[XSUtilities urlForImageObject:object]]; 

        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:([imagesArray count] - 1) inSection:0]; 
        NSLog(@"New row: %d", indexPath.row); 
        [newIndexPaths addObject:indexPath]; 
       } 

       if ([newIndexPaths count] > 0) { 
        [UIView animateWithDuration:0.25 animations:^{loadingLabel.alpha = 0.0;}]; 
        [feed insertItemsAtIndexPaths:newIndexPaths]; 
        //[feed scrollToItemAtIndexPath:newIndexPaths[0] atScrollPosition:UICollectionViewScrollPositionCenteredVertically animated:NO]; 

        NSLog(@"imagesArray count: %d", [imagesArray count]); 

        //[feed reloadData]; 

        page += 1; 
       } else { 
        NSLog(@"Got back no objects"); 
       } 
      } 

     } 
     isLoadingNextPage = NO; 
    }]; 
} 

然後我發現當用戶滾動到頁面的底部，並使用此代碼加載下一組：

- (void)scrollViewDidScroll:(UIScrollView *)aScrollView { 

    CGPoint offset = aScrollView.contentOffset; 
    CGRect bounds = aScrollView.bounds; 
    CGSize size = aScrollView.contentSize; 
    UIEdgeInsets inset = aScrollView.contentInset; 

    float y = offset.y + bounds.size.height - inset.bottom; 
    float h = size.height; 

    float reload_distance = 480; 
    if(y > h - reload_distance) { 
     NSLog(@"Hit the load point"); 

     if (!isLoadingNextPage) { 
      NSLog(@"Loading page %d", page); 
      isLoadingNextPage = YES; 
      [self loadImagesStartingAtNum:(page * 12) withRefresh:NO]; 
     } 

    } 

} 

Answer 1

難，沒有看到你的代碼來回答。

您可以嘗試使用scrollToItemAtIndexPath方法嗎？

- (void)scrollToItemAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UICollectionViewScrollPosition)scrollPosition animated:NO 

您可以滾動到任何你想要的位置。