Question

我使用collectionView在从Coredatabase抓取后显示图片。但是，除了numberOfItemsInSection＆amp; numberOfSectionsInCollectionView。代理和数据源设置正确。

单元格的标识符是photoCell，类是JLTPhotoCell。

- (void)viewDidLoad
        {
            [super viewDidLoad];
            _thumbNails = [[NSArray alloc]init]; // its declared ,don't worry about this
            _thumbNails = [[LADataModelController getSingleton] getAllSignatures];

            UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
            [layout setItemSize:( CGSizeMake(50,50))];
            [_collectionView setCollectionViewLayout:layout];
            self.collectionView.delegate = self;
            self.collectionView.dataSource = self;
            [_collectionView registerClass:[JLTPhotoCell class] forCellWithReuseIdentifier:@"photoCell"];
            [self.view addSubview:self.collectionView];
            self.collectionView.allowsSelection = true;
    }

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section
{
    NSLog(@"count %i" , _thumbNails.count);
    return _thumbNails.count;
}

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

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    if (_thumbNails.count > 0)
    {
        JLTPhotoCell *cell = [cv dequeueReusableCellWithReuseIdentifier:@"photoCell" forIndexPath:indexPath];

        NSData *thumbnailData = ((LASignature*)[_thumbNails objectAtIndex:indexPath.row]).signatureImage;
        UIImage* thumbnailImage = [UIImage imageWithData:thumbnailData];
        [cell setThumbnail:thumbnailImage];
        NSLog(@"image:%@",thumbnailImage);

        if (!_buttonSelect.hidden)
        {
            [cell performSelected:FALSE];
        }

        return cell;
    }

    return nil;
}

#pragma mark UICollectionViewDelegate Methods

-(void) collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    _lastSelectedSign = [_thumbNails objectAtIndex:indexPath.row];

    if (!self.buttonSelect.hidden)
    {
        JLTPhotoCell *cell = (JLTPhotoCell *)[_collectionView cellForItemAtIndexPath:indexPath];
        cell.selected = FALSE;

    }
    else
    {
        [_selectedImages addObject:[_thumbNails objectAtIndex:indexPath.row]];
        JLTPhotoCell *cell = (JLTPhotoCell *)[_collectionView cellForItemAtIndexPath:indexPath];
        [cell performSelected:TRUE];
      //  _buttonDelete.enabled = _selectedImages.count > 0;
    }

}

-(void) collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
{
    [_selectedImages removeObject:[_thumbNails objectAtIndex:indexPath.row]];

    JLTPhotoCell *cell = (JLTPhotoCell *)[_collectionView cellForItemAtIndexPath:indexPath];
    [cell performSelected:FALSE];
    _buttonDelete.enabled = _selectedImages.count > 0;

}

#pragma mark - UICollectionViewDelegateFlowLayout
-(CGSize) collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
   return  CGSizeMake(50,50) ;
}

-(UIEdgeInsets) collectionView:(UICollectionView *)collectionView layout:(UICollectionViewFlowLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    collectionViewLayout.minimumInteritemSpacing=1;
    collectionViewLayout.minimumLineSpacing =2;
    return UIEdgeInsetsMake(1, 1, 1, 1);
}

jltPhotoCell Class
-(void) setThumbnail:(UIImage *) thumbnail
{
    [self setThumbnail:thumbnail andWithSize:(CGSizeMake(50,50))];
}

-(void) setThumbnail:(UIImage *) thumbnail andWithSize:(CGSize) size
{
    UIImageView *thumbImageView = [[UIImageView alloc] initWithImage:thumbnail];
    thumbImageView.frame = CGRectMake(0,0,size.width,size.height);
    thumbImageView.userInteractionEnabled = YES;
    [self.contentView addSubview:thumbImageView];
}

-(void) performSelected:(bool)selected
{
    if (selected)
    {
        UIImageView *deleteImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"delete"]];
        deleteImageView.frame = CGRectMake(self.contentView.frame.size.width - 35, 3, 32, 32);
        deleteImageView.tag = 123;
        [self.contentView addSubview:deleteImageView];
    }
    else
    {
        UIView *v = [self.contentView viewWithTag:123];
        v.hidden = YES;
        [self.contentView bringSubviewToFront:v];
        [v removeFromSuperview];
    }
}

任何建议都将不胜感激。感谢。

Answer 1

@highlycaffeinated我遇到了这个问题。但是，调用invalidateLayout并不适合我。

但是，在数据源工作之后分配代理。

我改变了：

self.collectionView.delegate = self;
self.collectionView.dataSource = self;

使用：

self.collectionView.dataSource = self;
self.collectionView.delegate = self;

Answer 2

我遇到了同样的问题。在分配数据源后，我可以通过调用布局invalidateLayout来解决它。

Answer 3

仅适用于会遇到类似UICollectionViews问题的人，尤其是在以编程方式执行此操作时。所以我有同样的问题，终于发现我在数组中有零元素，应该在collectionView中填充。因此，在阅读文档之后，它说集合视图将不会显示，除非从阵列中显示至少一个元素，否则它将一直给你黑屏。在这种情况下可能发生的另一个问题是sizeForItemAtIndexPath将在cellForItemAtIndexPath之前被调用，因为像标签和图像的单元格内容不会占用自己的高度，而是单元格本身的高度。希望这个答案会帮助周围的人。

cellForItemAtIndexPath，sizeForItemAtIndexPath，insetForSectionAtIndex未被调用iOS

3 个答案: