如何使用 UIViewControllerRepresentable 在 SwiftUI 中呈现 UICollectionView

Question

首先，我知道可以选择使用 SwiftUI 列表等来获得类似的效果。但我需要 UICollectionView 的自动滚动功能，所以我真的很想实现一个“老派”版本。我什至不想要理想的构图布局版本。

我当前的代码如下所示：

import SwiftUI

struct CollectionView: UIViewControllerRepresentable {

private var isActive: Binding<Bool>
private let viewController = UIViewController()
private let collectionController: UICollectionView

init(_ isActive: Binding<Bool>) {
    self.isActive = isActive
    self.collectionController = UICollectionView(frame: CGRect(x: 0, y: 0, width: 100, height: 200), collectionViewLayout: UICollectionViewFlowLayout())
}
func makeUIViewController(context: UIViewControllerRepresentableContext<CollectionView>) -> UIViewController {
    return viewController
}

func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<CollectionView>) {
    if self.isActive.wrappedValue && collectionController.delegate == nil { // to not show twice
        collectionController.delegate = context.coordinator
        collectionController.dataSource = context.coordinator
    }
}

func makeCoordinator() -> Coordintor {
    return Coordintor(owner: self)
}

final class Coordintor: NSObject, UICollectionViewDelegate, UICollectionViewDataSource {
    weak var viewController:UIViewController?
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 3
    }
    var cellId = "Cell"
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath)
        return cell
    }
    // works as delegate
    let owner: CollectionView
    init(owner: CollectionView) {
        self.owner = owner

    }
}
}

不幸的是，我得到的只是预览中的空白屏幕。现在，如果我可以显示大量红色方块，我可以滚动它们并在出现时自动滚动到底部，那就太理想了。

谢谢！

Answer 1

这是最小的可运行演示。（注意：如果所有操作都以编程方式完成，则必须注册单元格）

class MyCell: UICollectionViewCell {
}

struct CollectionView: UIViewRepresentable {
    func makeUIView(context: Context) -> UICollectionView {
        let view = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
        view.backgroundColor = UIColor.clear
        view.dataSource = context.coordinator

        view.register(MyCell.self, forCellWithReuseIdentifier: "myCell")
        return view
    }

    func updateUIView(_ uiView: UICollectionView, context: Context) {
    }

    func makeCoordinator() -> Coordinator {
        Coordinator()
    }

    class Coordinator: NSObject, UICollectionViewDataSource {
        func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
            3
        }

        func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "myCell", for: indexPath) as! MyCell
            cell.backgroundColor = UIColor.red
            return cell
        }
    }
}

struct TestUICollectionView_Previews: PreviewProvider {
    static var previews: some View {
        CollectionView()
    }
}