ios - collectionViewLayout sizeForItemAtIndexPath -> CGSize 奇怪的行为

Question

所以很有趣，我正在尝试使用 collectionViewLayout sizeForItemAtIndexPath 在 collectionView 中一次只显示一个项目并水平滚动，我试过这个:

- (void)viewDidLoad {
    [super viewDidLoad];

    flowLayout = [[UICollectionViewFlowLayout alloc]init];
    
    flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    flowLayout.minimumInteritemSpacing = 0.0;
    
    flowLayout.minimumLineSpacing = 0.0;
    
    _obj_CollectionView.pagingEnabled = YES;
    _obj_CollectionView.collectionViewLayout = flowLayout;
    
    self.obj_CollectionView.delegate = self;
    self.obj_CollectionView.dataSource = self;
    _obj_CollectionView.backgroundColor = [UIColor redColor];
}


-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    return CGSizeMake(collectionView.frame.size.width, collectionView.frame.size.height);
}

这是 collectionView 截图:

这里紫色是我的单元格，红色是我的 collectionView 但我想要整个紫色。

所以请指导我。我很迷惑。 :)

Answer 1

首先，您不需要以编程方式创建UICollectionViewFlowLayout 的对象。也不需要 viewDidLoad() 中编写的代码。您可以使用 storyboard 和 delegate 方法完成所有这些操作。

下面是你的问题的代码:

import UIKit

class ViewController: UIViewController
{
    @IBOutlet weak var collectionView: UICollectionView!

    override func viewDidLoad()
    {
        super.viewDidLoad()
    }
}

extension ViewController : UICollectionViewDataSource
{
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
    {
        return 10
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
    {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = (indexPath.item % 2 == 0) ? UIColor.purple : UIColor.blue
        return cell
    }
}

extension ViewController : UICollectionViewDelegateFlowLayout
{
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
    {
        return CGSize(width: collectionView.bounds.width, height: collectionView.bounds.height)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat
    {
        return 0
    }

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets
    {
        return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    }
}

Storyboard截图:

输出屏幕: