SwiftUI：UIAlertController 的 textField 在 UIAlertAction 中没有响应

Question

我需要使用UIAlertContoller，因为SwiftUI 的Alert 不支持TextField。

由于各种原因（可访问性、DynamicType、暗模式支持等），我不能使用自定义创建的 AlertView。

基本思想是，SwiftUI 的警报必须保持 TextField 并且输入的文本必须反射回来才能使用。

我通过遵循 UIViewControllerRepresentable 创建了一个 SwiftUI view 以下是工作代码。

struct AlertControl: UIViewControllerRepresentable {

    typealias UIViewControllerType = UIAlertController

    @Binding var textString: String
    @Binding var show: Bool

    var title: String
    var message: String

    func makeUIViewController(context: UIViewControllerRepresentableContext<AlertControl>) -> UIAlertController {

        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)

        alert.addTextField { textField in
            textField.placeholder = "Enter some text"
        }

        let cancelAction = UIAlertAction(title: "cancel", style: .destructive) { (action) in
            self.show = false
        }

        let submitAction = UIAlertAction(title: "Submit", style: .default) { (action) in
            self.show = false
        }

        alert.addAction(cancelAction)
        alert.addAction(submitAction)

        return alert
    }

    func updateUIViewController(_ uiViewController: UIAlertController, context: UIViewControllerRepresentableContext<AlertControl>) {

    }

    func makeCoordinator() -> AlertControl.Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject, UITextFieldDelegate {

        var control: AlertControl

        init(_ control: AlertControl) {
            self.control = control
        }

        func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
            if let text = textField.text {
                self.control.textString = text
            }

            return true
        }
    }
}

// SwiftUI View in some content view
 AlertControl(textString: self.$text,
                             show: self.$showAlert,
                             title: "Title goes here",
                             message: "Message goes here")

问题：

点击警报操作时没有任何活动。我设置了断点来检查，但它从来没有打到那里。

即使是UITextFieldDelegate 的函数也没有命中。

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool

编辑：cancelAction 或 submitAction 不会在点击这些字段时触发。

Answer 1

这是适用于解决方案的完整演示模块。使用 Xcode 13.3 / iOS 14.0+ 测试

另见重要的 cmets inline

import SwiftUI

struct CustomAlert: UIViewControllerRepresentable {
    @Binding var text: String
    @Binding var isPresented: Bool
    var title: String
    var message: String
    var onSubmit: (() -> ())?
    var onCancel: (() -> ())?
    
    func makeUIViewController(context: Context) -> UIViewController {
        UIViewController() // holder controller - required to present alert
    }
    
    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
        guard context.coordinator.alert == nil else { return }
        if isPresented {
            let alert = makeAlert(with: context)
            context.coordinator.alert = alert
            Task {
                uiViewController.present(alert, animated: true) {
                    self.isPresented = false  // hide holder after alert dismiss
                    context.coordinator.alert = nil
                }
            }
        }
    }
    
    private func makeAlert(with context: Context) -> UIAlertController {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addTextField { textField in
            textField.placeholder = "Enter some text"
            textField.text = text                       // << initial value if any
            textField.delegate = context.coordinator    // << use coordinator as delegate
        }
        alert.addAction(cancelAction)
        alert.addAction(submitAction)
        return alert
    }
    
    private var cancelAction: UIAlertAction {
        UIAlertAction(title: "cancel", style: .destructive) { _ in
            onCancel?()
        }
    }
    
    private var submitAction: UIAlertAction {
        UIAlertAction(title: "Submit", style: .default) { _ in
            onSubmit?()
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    class Coordinator: NSObject, UITextFieldDelegate {
        var parent: CustomAlert
        var alert: UIAlertController?
        
        init(_ parent: CustomAlert) {
            self.parent = parent
        }
        
        func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
            if let text = textField.text as NSString? {
                parent.text = text.replacingCharacters(in: range, with: string)
            } else {
                parent.text = ""
            }
            return true
        }
    }
}

struct DemoCustomAlert: View {
    @State private var text = ""
    @State private var alertIsDisplayed = false
    
    var body: some View {
        VStack {
            Button {
                alertIsDisplayed.toggle()
            } label: {
                Text("Alert")
            }
            .background(
                CustomAlert(
                    text: $text,
                    isPresented: $alertIsDisplayed,
                    title: "Title goes here",
                    message: "Message goes here",
                    onSubmit: { print("didSubmit") },
                    onCancel: { print("didCancel") }
                )
            )
            Text(text)
        }
    }
}