创建一个空的集合视图单元格会引发错误

Question

我正在使用 UICollectionView 和自定义 UICollectionViewCell。

我使用以下方法创建了一个空单元格：

[[MyCell alloc] init];

编译器抛出错误：

Assertion failure in -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:]

我在viewDidLoad:方法中尝试了以下：

[self.collection registerClass:[MyCell class] forCellWithReuseIdentifier:@"MyCell"];

然后在- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath方法中：

MyCell *cell = [[MyCell alloc] init];

Answer 1

如果集合视图尚不存在，则必须告诉集合视图如何创建相应的视图。为此，您必须在集合视图中注册类或 nib 文件。使用这些方法中的任何一种

- (void)registerClass:(Class)cellClass forCellWithReuseIdentifier:(NSString *)identifier;
- (void)registerClass:(Class)viewClass forSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier;
- (void)registerNib:(UINib *)nib forCellWithReuseIdentifier:(NSString *)identifier;
- (void)registerNib:(UINib *)nib forSupplementaryViewOfKind:(NSString *)kind withReuseIdentifier:(NSString *)identifier;

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Answer 2

在实现文件中创建一个常量NSString 标识符。

static NSString * const CustomClassCellIdentifier = @"Cell";

然后在viewDidLoad:

[self.collectionView registerNib:[UINib nibWithNibName:@"CustomClassCell" bundle:nil] forCellWithReuseIdentifier:CustomClassCellIdentifier];

//[self.collectionView registerClass:[CustomClassCell class] forCellWithReuseIdentifier:CustomClassCellIdentifier];

然后在dataSource方法中

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView 
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CustomClassCell *customCell =
        [collectionView dequeueReusableCellWithReuseIdentifier:CustomClassCellIdentifier
                  forIndexPath:indexPath];

    return customCell;
}