ios - 即使设置了委托(delegate)，UICollectionView didSelectItemAtIndexPath 也从未调用过

Question

我只是想在 UIViewController 中做一个普通的 UICollectionView。一切都按预期工作，只是当我触摸 CollectionViewCell 以选择它时没有任何反应。这是我的代码的骨架:

@interface CreateNewFieldViewController () <UITextFieldDelegate, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout>

- (void) viewDidLoad {
...
    UICollectionViewFlowLayout* flowLayout = [[UICollectionViewFlowLayout alloc]init];
    flowLayout.itemSize = CGSizeMake(self.width*.15, self.width*.15);
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];
    flowLayout.minimumInteritemSpacing = 30;
    flowLayout.minimumLineSpacing = 30;   

    self.collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(self.width*.1, self.height*.2, self.width*.8, self.height*.3) collectionViewLayout:flowLayout];

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

    self.collectionView.allowsSelection = YES;
    self.collectionView.allowsMultipleSelection = NO;

    self.collectionView.bounces = YES;
    self.collectionView.alwaysBounceHorizontal = YES;
    self.collectionView.alwaysBounceVertical = YES;
    [self.collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
    [self.view addSubview:self.collectionView];

    self.collectionView.backgroundColor = [UIColor clearColor];
...
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    self.fieldNameInput.text = self.backgroundImageNames[indexPath.row];
    NSLog(@"recording this: %@", self.fieldNameInput.text);
}

数据源和流布局工作得很好，但出于某种原因，当我点击一个单元格时，没有任何反应。我没有看到任何日志语句，所以我知道 didSelect 没有被调用。我错过了什么？

---

看起来这可能是外行人的陷阱，但我仍然找不到它是什么。参见例如这个blog post .

Answer 1

对 UICollectionView 的额外调用解决了这个问题:

[collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];

和

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    cell.selected = YES;
    [collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];
    return cell;
}