断言失败 - [UICollectionViewData numberOfItemsBeforeSection:]

Question

使用IOS 6和新的UICollectionView我在UIViewController上有2个UICollectionView并使用Storyboard当我点击UICollectionView时我得到以下错误我不知道为什么会发生这种情况并且Google返回0结果这个错误...

2012-10-13 20:30:06.421 MyApp [768:907]断言失败 - [UICollectionViewData numberOfItemsBeforeSection:],/ SourceCache/UIKit/UIKit-2372/UICollectionViewData.m:415
2012-10-13 20:30:06.427 MyApp [768:907]由于未捕获的异常'NSInternalInconsistencyException'而终止应用程序,原因:'当在集合视图中只有1个部分时,请求部分2147483647之前的项目数'

我根本没有使用Sections,只将它设置为1个部分:

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}

当我点击UICollectionView区域时,它会发生(似乎是随机的)我有一段代码从UICollectionView中删除元素:

[tilesArray removeObjectAtIndex:indexPath.row];
[self.tilesCollectionView reloadData];        
[resultsArray addObject:str];
[self.resultsCollectionView reloadData];

以下是数组如何连接到UICollectionViews

-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {

    if(collectionView.tag == 2)
        return [resultsArray count];
    else
        return [tilesArray count];
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

    if(collectionView.tag == 2)
    {
        static NSString *cellIdentifier = @"ResultCell";
        ResultCell *cell = (ResultCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

        cell.mainImage.image = [UIImage imageNamed:currentArtContainer.tileMainImage];

        NSString *cellData = [resultsArray objectAtIndex:indexPath.row];
        [cell.titleLabel setText:cellData];

        return cell;
    }
    else
    {
        static NSString *cellIdentifier = @"TileCell";
        TileCell *cell = (TileCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

        cell.topImage.image = [UIImage imageNamed:currentArtContainer.tileTopImage];

        cell.mainImage.image = [UIImage imageNamed:currentArtContainer.tileMainImage];

        NSString *cellData = [tilesArray objectAtIndex:indexPath.row];
        [cell.titleLabel setText:cellData];

        return cell;
    }
}

请帮我解决这个问题.甚至不确定如何捕获异常,因为它来自UICollectionView内部代码.也忘了提到我正在使用UICollectionView的自定义布局,但我不知道它是否与此问题有关.

再次感谢您的帮助!

编辑:我在调用所有布局方法后得到异常...这是我的自定义布局...我仍然不确定如何修复它,因为我的所有try catch块都没有捕获错误. ..

- (void)prepareLayout
{
    NSLog(@"In prepareLayout.");

    [super prepareLayout];
    _cellCount = [[self collectionView] numberOfItemsInSection:0];
}

- (CGSize)collectionViewContentSize
{
    NSLog(@"In collectionViewContentSize.");
    @try {

       CGSize csize = [self collectionView].frame.size;
        NSLog(@"In here.");
        return csize;
    }
    @catch(NSException *exception)
    {
        NSLog(@"collectionViewContentSize %@: %@",[exception name],[exception reason]);
    }

}

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    @try {

    NSLog(@"In layoutAttributesForItemAtIndexPath. item %d", indexPath.row);


    UICollectionViewLayoutAttributes* attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];

    attributes.size = CGSizeMake(ITEM_SIZE, ITEM_SIZE);

    NSLog(@"firstRun %d", self.firstRun);
    //NSLog(@"panStatus %@", self.panStatus);

    if (self.firstRun == 0) {
        CGFloat x = 0, y = 0;
        CGFloat boundx = self.collectionView.frame.size.width * 0.70;   // Use the whole canvas
        CGFloat boundy = self.collectionView.frame.size.height * 0.70; // Use the whole canvas
        while (x < 50 || x > boundx) x = arc4random() % (int)boundx + indexPath.item;
        while (y < 50 || y > boundy) y = arc4random() % (int)boundy + indexPath.item;

        NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
        if (self.positions)
            dictionary = [self.positions mutableCopy];
        [dictionary setObject:[NSValue valueWithCGPoint:CGPointMake(x, y)] forKey:@(indexPath.item)];
        if (!self.positions)
            self.positions = [[NSDictionary alloc] init];
        self.positions = dictionary;

        attributes.center = CGPointMake(x, y);
    } else if (self.firstRun > 0) {
        CGPoint point = [[self.positions objectForKey:@(indexPath.item)] CGPointValue];
        attributes.center = CGPointMake(point.x, point.y);
    }

    NSLog(@"END layoutAttributesForItemAtIndexPath. item %d", indexPath.row);
        return attributes;

    }
    @catch(NSException *exception)
    {
        NSLog(@"layoutAttributesForItemAtIndexPath %@: %@",[exception name],[exception reason]);
    }
}

-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    @try {

    NSLog(@"layoutAttributesForElementsInRect ...");

    NSMutableArray* attributes = [NSMutableArray array];
    for (NSInteger i=0 ; i < self.cellCount; i++) {
        NSIndexPath* indexPath = [NSIndexPath indexPathForItem:i inSection:1];
        [attributes addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
    }
    NSLog(@"END layoutAttributesForElementsInRect ...");
        return attributes;

    }
    @catch(NSException *exception)
    {
        NSLog(@"layoutAttributesForElementsInRect %@: %@",[exception name],[exception reason]);
    }
}

Answer 1

我从手势识别器运行reloadData时遇到这种情况,在手势识别器上设置delayedTouchesBegan帮助.

Answer 2

这里的关键是你的错误中的这个数字:

2147483647

这是数值NSNotFound.在代码中的某处,您正在执行类似于indexOfObject:数组的操作,并将其结果作为段或项索引传递到您的集合视图或布局方法之一,这会导致错误.这不会发生在您的问题中发布的代码中,但希望您现在能够找到它.

Answer 3

这对我有用:

dispatch_async(dispatch_get_main_queue(), ^{
    [self.collectionView reloadData];
});