IOS UICollectionView 在使用两个 Collection View 时抛出断言

Question

我在一个 UIViewController 中有两个 UICollectionView。我通过标记号将它们分开，以便我可以对两者使用数据源和委托(delegate)方法。但是，当我运行代码时，它会因异常而崩溃:

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UICollectionView received layout attributes for a cell with an index path that does not exist: <NSIndexPath: 0xc000000000200016> {length = 2, path = 0 - 1}' .

我在论坛上查过这个，大多数人说你需要使 UIControllerView 失效然后重新加载，但在我的例子中这是行不通的。

有人知道如何解决这个问题吗？

这是我的代码:

-(void)viewDidLoad {

    self.socialMediaGrayIcons = [[NSMutableArray alloc] initWithObjects:[UIImage imageNamed:@"fb-gray.png"],
                            [UIImage imageNamed:@"twitter-gray.png"],
                            [UIImage imageNamed:@"insta-gray.png"],
                            [UIImage imageNamed:@"sms-gray.png"],
                            [UIImage imageNamed:@"email-gray.png"], nil];

    // setup collection view
    self.avatarCollectionView.tag = 200;
    self.socialMediaCollectionView.tag = 201;

    UINib *cellNib = [UINib nibWithNibName:@"NibCell" bundle:nil];
    [self.avatarCollectionView  registerNib:cellNib forCellWithReuseIdentifier:@"cvCell"];
    [self.socialMediaCollectionView  registerNib:cellNib forCellWithReuseIdentifier:@"smCell"];

    // setup collection view layout
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    [flowLayout setItemSize:CGSizeMake(40, 40)];
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];

    [self.avatarCollectionView setCollectionViewLayout:flowLayout];
    [self.socialMediaCollectionView setCollectionViewLayout:flowLayout];

    [self.avatarCollectionView reloadData];
    [self.avatarCollectionView.collectionViewLayout invalidateLayout];

    [self.socialMediaCollectionView reloadData];
    [self.socialMediaCollectionView.collectionViewLayout invalidateLayout];
}

....

#pragma mark UICollectionView DataSource and Delegate mathods
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    if (collectionView.tag == 200)
    {
        return self.children.count;
    } else if (collectionView.tag == 201){
        return self.socialMediaGrayIcons.count;
    }

    return 1;
}


- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell;

    if (collectionView.tag == 200)
    {
        static NSString *cellIdentifier = @"cvCell";
        cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

        Child *currentChild = [self.children objectAtIndex:indexPath.row];


        UIImage *curImage = [UIImage imageWithData:currentChild.thumbnail];
        UIImageView *thumbView = (UIImageView *)[cell viewWithTag:100];

        if (curImage != nil)
        {
            [thumbView setImage:curImage];

        }
    } else if (collectionView.tag == 201){

        static NSString *cellIdentifier = @"smCell";
        cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

        UIImage *curImage = (UIImage*) [self.socialMediaGrayIcons objectAtIndex:indexPath.row];
        UIImageView *thumbView = (UIImageView *)[cell viewWithTag:101];

        if (curImage != nil)
        {
            [thumbView setImage:curImage];

        }
    }

    return cell;
}

Answer 1

采纳@Paulw 的好建议是这样的:

@property(weak,nonatomic) IBOutlet UICollectionView *collectionViewA;
@property(weak,nonatomic) IBOutlet UICollectionView *collectionViewB;

您的数据源方法必须始终根据传递的 Collection View 划分为条件的两个分支，并且始终在一个中使用一个数据源数组，在另一个中使用另一个。

您可以始终通过一种方便的方法获取您的数据源，例如这样...

- (NSArray *)datasourceForCollectionView:(UICollectionView *)collectionView {
    if (collectionView == self.collectionViewA) {
        return self.children;
    } else { // NOTICE - no else-if, there's no other valid condition
        return self.socialMediaGrayIcons;
    }
}

在任何地方都可以使用它，例如...

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return [self datasourceForCollectionView:collectionView].count;
}