UICollectionView didDeselectItemAtIndexPath不獲取單元格

Question

我有一個簡單的collectionView，並使用didSelectItemAtIndexPath和didDeselectItemAtIndexPath更改單元格的背景色。

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
    cell.contentView.backgroundColor = [UIColor lightGrayColor];
}

- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath{
    UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
    cell.contentView.backgroundColor = [UIColor clearColor];
}

一切正常，但是如果我選擇一個單元格，則滾動列表（我選擇的單元格不在屏幕上），然后選擇另一個，在didDeselectItemAtIndexPath我的“單元格”變量為nil。 為什么？

注意：僅當所選單元格不在屏幕上時

Answer 1

以適當的方式簡單地選擇和取消選擇單元格后面的邏輯：

ViewController.h

 int selectedIndex;

ViewController.m

- (void)viewDidLoad 
{
      [super viewDidLoad];
      selectedIndex = -1;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
  {
        static NSString *identifier = @"CollectionCell";
        WalletCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];

        if(indexPath.row == selectedIndex)
        {
               cell.selected = YES;
               cell.backgroundColor = [UIColor redColor];
        }
        else
        {
               cell.selected = NO;
               cell.backgroundColor = [UIColor clearColor];
        }
          return cell;
  }


- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
     UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
      selectedIndex = (int)indexPath.row;
       cell.backgroundColor = [UIColor redColor];
}

 - (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
 {
       UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
       cell.backgroundColor = [UIColor clearColor];
 }