SwiftUI: UIAlertController's textField does not responding in UIAlertAction

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春和景丽
春和景丽 2021-01-23 12:57

I need to use UIAlertContoller, as SwiftUI\'s Alert does not support TextField.

I must not use Custom created AlertView, due to v

1条回答
  •  醉梦人生
    2021-01-23 14:01

    Here is full demo module for solution that works. Tested with Xcode 11.4 / iOS 13.4

    See also important comments inline

    struct AlertControl: UIViewControllerRepresentable {
    
        @Binding var textString: String
        @Binding var show: Bool
    
        var title: String
        var message: String
    
        func makeUIViewController(context: UIViewControllerRepresentableContext) -> UIViewController {
            return UIViewController() // holder controller - required to present alert
        }
    
        func updateUIViewController(_ viewController: UIViewController, context: UIViewControllerRepresentableContext) {
            guard context.coordinator.alert == nil else { return }
            if self.show {
                let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
                context.coordinator.alert = alert
    
                alert.addTextField { textField in
                    textField.placeholder = "Enter some text"
                    textField.text = self.textString            // << initial value if any
                    textField.delegate = context.coordinator    // << use coordinator as delegate
                }
                alert.addAction(UIAlertAction(title: "cancel", style: .destructive) { _ in
                    // your action here
                })
                alert.addAction(UIAlertAction(title: "Submit", style: .default) { _ in
                    // your action here
                })
    
                DispatchQueue.main.async { // must be async !!
                    viewController.present(alert, animated: true, completion: {
                        self.show = false  // hide holder after alert dismiss
                        context.coordinator.alert = nil
                    })
                }
            }
        }
    
        func makeCoordinator() -> AlertControl.Coordinator {
            Coordinator(self)
        }
    
        class Coordinator: NSObject, UITextFieldDelegate {
            var alert: UIAlertController?
            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 as NSString? {
                    self.control.textString = text.replacingCharacters(in: range, with: string)
                } else {
                    self.control.textString = ""
                }
                return true
            }
        }
    }
    
    // Demo view for Alert Controll
    struct DemoAlertControl: View {
        @State private var text = ""
        @State private var showAlert = false
    
        var body: some View {
            VStack {
                Button("Alert") { self.showAlert = true }
                    .background(AlertControl(textString: self.$text, show: self.$showAlert,
                             title: "Title goes here", message: "Message goes here"))
                Text(self.text)
            }
        }
    }
    

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