我的 UICollectionView 没有调用它的数据源方法？

Question

我刚刚有了一个标准的UIViewController 子类和一个UICollectionView。 UICollection 视图没有调用它的数据源（或委托）方法，但我看不到哪一块丢失了。

这是呈现 UICollectionView 的 UIViewController 类的界面：

@interface PastViewController ()  <UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout>
...
@property (nonatomic, weak) UICollectionView *collectionView;
@end

这是我的 viewDidLoad（几乎）的全部内容：

- (void)viewDidLoad {

    [super viewDidLoad];    


    UICollectionViewFlowLayout* flowLayout = [[UICollectionViewFlowLayout alloc]init];
    flowLayout.itemSize = CGSizeMake(100, 100);
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];

    //self.complaints is used to generate the collection view cells
    //the log always prints out 30 complaints
    self.complaints = [self.complaintDatabase getComplaints ];
    NSLog(@"got a total OF %d complaints", self.complaints.count);

    self.collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, self.width, self.height) collectionViewLayout:flowLayout];
    self.collectionView.delegate = self;
    self.collectionView.dataSource = self;
    [self.collectionView registerClass:[VideoCollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
    [self.view addSubview:self.collectionView];


    [self.collectionView reloadData];
    [self.collectionView reloadInputViews];
}

我还将在最后发布数据源、委托和委托流布局协议。视图控制器中没有添加其他子视图，并且我已经设置了委托并声明了委托协议，因此以下 SO 帖子不适用：

• UICollectionView doesn't call delegate methods
• UIcollection view not getting call datasources

我错过了什么？为什么永远不会调用数据源方法（和委托方法）？

以下是为各种协议实现的方法：

#pragma mark - UICollectionViewDataSource

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

    NSLog(@"should be seeing %d collection view cells", self.complaints.count);
    return self.complaints.count;
}


- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
    NSLog(@"QUERYING NUMBER OF SECTIONS IN COLLECTION VIEW");
    return 1;
}


- (UICollectionViewCell  *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    VideoCollectionViewCell *cell = [[VideoCollectionViewCell alloc] initWithCoder:@"cell"];
    cell.complaint = self.complaints[indexPath.row];
    return cell;
}


#pragma mark - UICollectionViewDelegate

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    NSLog(@"calling didselctitem at path");
}

- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath{
    NSLog(@"diddeselectitem");
}


#pragma mar - UICollectionViewFlowDelegateLayout

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
    return CGSizeMake(100, 100);
}


- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
    return UIEdgeInsetsMake(50, 20, 50, 20);
}

Answer 1

@property (nonatomic, strong) UICollectionView *collectionView;

将weak更改为strong，否则collectionView将在赋值后被释放，这意味着collectionView将变为nil，这样就永远不会调用数据源方法。

另一种方法：

将collectionView 保留为weak。

- (void)viewDidLoad {

    [super viewDidLoad];    


    UICollectionViewFlowLayout* flowLayout = [[UICollectionViewFlowLayout alloc]init];
    flowLayout.itemSize = CGSizeMake(100, 100);
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];

    //self.complaints is used to generate the collection view cells
    //the log always prints out 30 complaints
    self.complaints = [self.complaintDatabase getComplaints ];
    NSLog(@"got a total OF %d complaints", self.complaints.count);

    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, self.width, self.height) collectionViewLayout:flowLayout];
    collectionView.delegate = self;
    collectionView.dataSource = self;
    [collectionView registerClass:[VideoCollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
    [self.view addSubview:collectionView];
    self.collectionView = collectionView;

    [self.collectionView reloadData];
    [self.collectionView reloadInputViews];
}

见：Creating views programmatically Strong Vs Weak subviews in controller