我的UICollectionView不調用它的數據源方法？

Question

我剛剛有一個標準UIViewController子類UICollectionView。那UICollection視圖不調用它的數據源（或委託）方法，但我看不到哪一塊丟失。

下面是呈現UICollectionView爲我UIViewController類接口：

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

這裏是我的viewDidLoad（幾乎）的全部：

- (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]; 
} 

我還會發布的數據源，委託，並在最後委託流佈局協議。有添加到視圖控制器沒有其他的子視圖，我已經設置委託，宣佈委託協議，因此SO下列職位不適用：

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

我錯過了什麼？爲什麼數據源方法（和委託方法）永遠不會被調用？

下面是各種協議實現的方法：

#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;

變化weak到strong，或collectionView將分配之後被釋放，這意味着collectionView將nil使得數據源方法永遠不會被調用。

另一種方法：

保持collectionView是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]; 
} 

參見：Creating views programmatically Strong Vs Weak subviews in controller