在SwiftUI中处理UITextView的UIResponder

Question

我正在尝试为SwiftUI中现有的UITextView子类处理UIResponder。我已经能够使用协调器模式来处理UITextViewDelegate，但是我在使用UIResponder时遇到了问题。

在过去(使用UIKit)，我要做的是使用NotificationCenter在UIViewController的子类中添加UIResponder.keyboardWillShowNotification的观察者。

在SwiftUI中，我不知道该把它放在哪里。我做了一件简单的事情，那就是重用makeUIView中的协调器类，如下所示：

    let nc = NotificationCenter.default
    nc.addObserver(context.coordinator, selector: #selector(Coordinator.keyboardWillShow(notification:)), name: UIResponder.keyboardWillShowNotification, object: editorTextView)

但是keyboardWillShow方法永远不会被调用。我做错了吗？

Answer 1

我建议您使用组合发布程序，这样您就不需要使用选择器了，但这两种方式都应该可以工作。在本例中，观察者/选择器模式被注释掉了，但是如果您取消注释它，当键盘出现时，观察者和发布者都应该响应。

    import Combine
    import SwiftUI
    import UIKit

    struct MyTextView: UIViewRepresentable {
    // Pass in the binding to the string from the SwiftUI view
    var text: Binding<String>

    init(text: Binding<String>) {
        self.text = text
    }

    func makeUIView(context: Context) -> UITextField {
        let tf = UITextField()
        tf.delegate = context.coordinator
        tf.text = context.coordinator.text.wrappedValue // Access the wrapped value in the binding
        return tf
    }

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

    func makeCoordinator() -> MyTextViewDelegate {
        let delegate = MyTextViewDelegate(text: text)
        return delegate
    }

    class MyTextViewDelegate: NSObject, UITextFieldDelegate {
//      let nc = NotificationCenter.default
        var text: Binding<String>

        // You can use a Combine Publisher rather than dealing with selectors
        var subscriber: AnyCancellable?

        init(text: Binding<String>) {
            self.text = text
            super.init()
            subscriber = NotificationCenter.default.publisher(for: UIResponder.keyboardWillShowNotification)
                .sink() { [weak self] note in
                    print(self?.text.wrappedValue ?? "nil")
                    print("Publisher called -> " + note.description)
            }
//            nc.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: UIResponder.keyboardWillShowNotification, object: nil)
        }


//        @objc func keyboardWillShow(notification: Notification) {
//            print("Selector called -> " + notification.description)
//        }

        // Value should update in SwiftUI when return key is pressed to show that the data flows
        func textFieldShouldReturn(_ textField: UITextField) -> Bool {
            self.text.wrappedValue = textField.text ?? ""
            print(textField.text!)
            return true
        }
    }
}