iOS 7:insertItemsAtIndexPaths:滚动UICollectionView

Question

我正在开发一个应用程序,我有一个无限滚动的UICollectionView图像.当用户到达页面底部时,我查询下一页图像,获取新的indexPaths,并将它们添加到UICollectionView中[collectionView insertItemsAtIndexPaths:newIndexPaths].

这一切都在iOS 6中完美运行.在iOS 7中它可以工作,但每次都会将用户滚动回到collectionView的顶部.我尝试过使用reloadData而且会发生同样的事情.

知道如何阻止这种滚动吗？

更新:包括我的代码

我有一个UICollectionView,以马赛克图案显示图像的缩略图(每个图像的大小不同,所以我正在使用RFQuiltLayout.我不认为这与滚动问题有任何关系,因为源代码没有似乎涉及滚动.

我使用以下代码从Parse后端加载每组12个图像.(如果isRefresh是,我清除了图像数组并再次加载第一页):

- (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;
    }];
}

然后我检测用户何时滚动到页面底部并使用以下代码加载下一组:

- (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

如果没有看到您的代码，很难回答。

你可以尝试使用scrollToItemAtIndexPath方法吗？

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

您可以滚动到任何您想要的位置。