支持滑动即可关闭工作表中显示的UIViewControllerRepresentable

Question

似乎如果你使用UIViewControllerRepresentable在你的SwiftUI应用程序中实现一个视图控制器，当你通过sheet呈现它时，你不能滑动它来关闭它。你需要做些什么来支持swipe解除吗？

struct ContentView: View {
    @State var showingPicker = false
    
    var body: some View {
        Text("Hello, world!")
            .onAppear {
                showingPicker = true
            }
            .sheet(isPresented: $showingPicker, content: {
                PHPicker() //cannot swipe to dismiss
                //Text("Test") //can swipe to dismiss
            })
    }
}

struct PHPicker: UIViewControllerRepresentable {
    func makeUIViewController(context: UIViewControllerRepresentableContext<PHPicker>) -> PHPickerViewController {
        let config = PHPickerConfiguration()
        return PHPickerViewController(configuration: config)
    }
    
    func updateUIViewController(_ uiViewController: PHPickerViewController, context: UIViewControllerRepresentableContext<PHPicker>) { }
}

Answer 1

可能的解决方案是添加类似句柄的东西来拖动(没有样式-简化了演示)，

​

​

.sheet(isPresented: $showingPicker, content: {
        VStack {
            RoundedRectangle(cornerRadius: 8).fill(Color.gray)
                .frame(width: 60, height: 8)
                .padding(.top, 8)
            PHPicker()
        }
})

替代：解决方案是完全由UIKit表示，只需在内部传递激活绑定即可表示。

这是一个可能的方法的演示。使用Xcode12.1/ iOS 14.1进行测试

​

​

struct PHPickerContentView: View {
    @State var showingPicker = false
    
    var body: some View {
        Button("Picker") {
           showingPicker = true
        }
        .background(PHPicker(isPresented: $showingPicker))    // << here !!
    }
}

struct PHPicker: UIViewControllerRepresentable {
    @Binding var isPresented: Bool

    func makeUIViewController(context: Context) -> UIViewController {
        UIViewController()   // << picker presenter
    }
    
    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
        // react on binding & show if not shown
        if isPresented && uiViewController.presentedViewController == nil {
            let config = PHPickerConfiguration()
            let picker = PHPickerViewController(configuration: config)
            picker.delegate = context.coordinator

            uiViewController.present(picker, animated: true)
            picker.presentationController?.delegate = context.coordinator
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    class Coordinator: NSObject, PHPickerViewControllerDelegate, UIAdaptivePresentationControllerDelegate {
        let owner: PHPicker
        init(_ owner: PHPicker) {
            self.owner = owner
        }

        func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {

            // picked image handling code here
        
            picker.presentingViewController?.dismiss(animated: true)
            owner.isPresented = false    // << reset on action !!
        }
        
        func presentationControllerDidDismiss(_ presentationController: UIPresentationController) {
            owner.isPresented = false    // << reset on swipe !!
        }
    }
}