在 UITextField 与 UIViewRepresentable 和 SwifUI 之间绑定文本时出现问题

Question

我正在尝试在 SwiftUI 中创建一个 'emoji picker'，它会弹出表情符号键盘，允许用户 select 表情符号，然后关闭键盘。我正在使用 UITextField 包装在带有字符串绑定的 UIViewRepresntable 中，但是由于某种原因，字符串的值永远不会更新。

这是我目前的代码：

/// Allows a user to pick an emoji character using the Emoji keyboard.
/// - Note: This does not prevent the user from manually switching to other keyboards and inputting a non-Emoji character
struct EmojiPicker: UIViewRepresentable {
    @Binding var emoji: String
    
    func makeUIView(context: UIViewRepresentableContext<EmojiPicker>) -> EmojiUITextField {
        let textField = EmojiUITextField(frame: .zero)
        textField.text = emoji
        textField.delegate = context.coordinator
        textField.autocorrectionType = .no
        textField.returnKeyType = .done
        textField.textAlignment = .center
        textField.tintColor = .clear
        
        return textField
    }
    
    func updateUIView(_ uiView: EmojiUITextField, context: Context) {
        self.emoji = uiView.text!
    }
    
    func makeCoordinator() -> EmojiTextFieldCoordinator {
        return EmojiTextFieldCoordinator(self)
    }
}

internal class EmojiTextFieldCoordinator: NSObject, UITextFieldDelegate {
    var emojiTextField: EmojiPicker
    
    init(_ textField: EmojiPicker) {
        self.emojiTextField = textField
    }
    
    func textFieldDidEndEditing(_ textField: UITextField) {
        self.emojiTextField.emoji = textField.text!
    }
    
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        textField.text = string
        
        if let text = textField.text, text.count == 1 {
            self.emojiTextField.emoji = textField.text!
            UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)
        }
        
        return true
    }
}

internal class EmojiUITextField: UITextField {
    override var textInputContextIdentifier: String? {
        return ""
    }

    override var textInputMode: UITextInputMode? {
        return UITextInputMode.activeInputModes.first {
            [=10=].primaryLanguage == "emoji"
        }
    }
    
    override func selectionRects(for range: UITextRange) -> [UITextSelectionRect] {
        return []
    }
}

到目前为止我找到的所有资源都没有用，包括 this, this, and this

Answer 1

这是修复，唯一修改的部分，（用Xcode 12 / iOS 14测试）

func updateUIView(_ uiView: EmojiUITextField, context: Context) {
    if self.emoji != uiView.text! {     // << update only on change, otherwise
        self.emoji = uiView.text!       // it result in cycle and dropped
    }
}

这是一个用于测试的视图

struct ContentView: View {
    @State private var text = "<none>"
    var body: some View {
        VStack {
            Text("Get: \(text)")
            EmojiPicker(emoji: $text)
        }
    }
}

在 UITextField 与 UIViewRepresentable 和 SwifUI 之间绑定文本时出现问题

Issue when binding text between UITextField with UIViewRepresentable and SwifUI

uitextfield

uikit

swiftui

uiviewrepresentable