UICollectionView 没有出现

Question

我正在尝试在扩展UIViewController 的视图控制器中设置UICollectionView 以编程方式。出于某种原因，我的收藏视图根本没有出现。以下是我所拥有的。

为什么没有出现？我将它连接到委托和数据源，并将其作为子视图添加到self.view。我的代码中缺少什么？

在我的.h 文件中：

@interface MainViewController : UIViewController
{
    @private
    UICollectionView *_collectionView;
    NSMutableArray *_results; // data source array
}
@end

在我的.m 文件中：

@interface MainViewController () <UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>
@property (nonatomic, retain) UICollectionView *collectionView;
@property (nonatomic, retain) NSMutableArray *results;
@end

@implementation MainViewController

@synthesize collectionView = _collectionView;
@synthesize results = _results;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // some init stuff - nothing to do with collection view.
    }

    return self;
}

- (void)loadView
{
    self.results = [NSMutableArray array];
    UIImage *image1 = [UIImage imageNamed:@"img1.jpg"];
    UIImage *image2 = [UIImage imageNamed:@"img2.jpg"];
    [self.results addObject:image1];
    [self.results addObject:image2];

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

    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];

    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) collectionViewLayout:flowLayout];
    self.collectionView = collectionView;

    [self.view addSubview:self.collectionView];

    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];
    [self.collectionView reloadData];

}

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section
{
    return [self.results count];
}

- (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView
{
    return 1;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    cell.backgroundColor = [UIColor colorWithPatternImage:[self.results objectAtIndex:indexPath.row]];
    return cell;
}


- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    UIImage *image = [self.results objectAtIndex:indexPath.row];    
    return CGSizeMake(image.size.width, image.size.height);
}

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

Answer 1

除非我将 loadView 方法更改为 viewDidLoad，否则我在尝试运行您的代码时遇到错误——根据您不应该直接调用 loadView 的文档。为了让数据源和委托方法运行，我将设置委托和数据源的行移到了 self 下面设置 self.collectionView = collectionView

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

Answer 2

您的numberOfSectionsInCollectionView: 返回0。对于包含一个部分的集合视图，您应该返回 1 或不实现此方法。

我也看不到你在哪里分配/初始化self.collectionView。

Answer 3

我最终继承了 UICollectionViewController 而不是 UIViewController 并将 init 方法更改为：

- (id)initWithCollectionViewLayout:(UICollectionViewLayout *)layout

它成功了。

Answer 4

您只需将 CollectionView 委托和数据源绑定到 StoryBoard 中的 ViewController。enter image description here