在 SwiftUI (UIViewRepresentable) 中向 UITextView 添加占位符

Question

我正在嘗試在使用 SwiftUI 制作的 textViews 中添加一個占位符，但是在執行textView.text = placeholder或textView.text = ""時，什么也沒有發生

使用textView.insertText(placeholder)有效，但是我不確定如何在輸入 textView 時刪除占位符（ textView.deleteBackward()中的每個字母可能）

這是我的 TextView.swift 代碼：

import Foundation
import SwiftUI
 
struct TextView: UIViewRepresentable {
    
    @Binding var text: String
    var placeholder: String
    let textStyle: UIFont.TextStyle
    @Binding var isFirstResponder: Bool
    
    let keyboard: String
 
    func makeUIView(context: Context) -> UITextView {
        let textView = UITextView()
        
        textView.delegate = context.coordinator
        textView.isSelectable = true
        textView.isUserInteractionEnabled = true
        textView.font = UIFont.preferredFont(forTextStyle: textStyle)
        textView.textAlignment = .center
        textView.autocapitalizationType = .none
        textView.autocorrectionType = .no
        textView.inputAssistantItem.leadingBarButtonGroups = []
        textView.inputAssistantItem.trailingBarButtonGroups = []
        if keyboard == "dummy" {
            let dummyBoard = NumKeyboard(frame: CGRect(x: 500, y: 500, width: 0, height: 0), textView: textView)
            textView.inputView = dummyBoard
        } else if keyboard == "num" {
            let keyboardView = NumKeyboard(frame: CGRect(x: 0, y: 0, width: 0, height: 300), textView: textView)
            textView.inputView = keyboardView
            keyboardView.delegate = context.coordinator
        } else if keyboard == "alphaNum" {
            let keyboardView = AlphaNumKeyboard(frame: CGRect(x: 0, y: 0, width: 0, height: 300),type: "UNIX", textView: textView)
            textView.inputView = keyboardView
            keyboardView.delegate = context.coordinator
        }


        textView.text = placeholder
        textView.textColor = UIColor.lightGray
        
        return textView
    }
 
    func updateUIView(_ uiView: UITextView, context: Context) {
        if uiView.text != text {
            uiView.text = text
        }
       
        DispatchQueue.main.async {
            if self.isFirstResponder && !uiView.isFirstResponder {
                uiView.becomeFirstResponder()
            }
            if !self.isFirstResponder && uiView.isFirstResponder {
                uiView.resignFirstResponder()
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator($text, $isFirstResponder, placeholder)
    }
     
    class Coordinator: NSObject, UITextViewDelegate, KeyboardDelegate {
        @Binding var text: String
        @Binding var isFirstResponder: Bool
        var placeholder: String
     
        init(_ text: Binding<String>, _ isFirstResponder: Binding<Bool>, _ placeholder: String) {
            _text = text
            _isFirstResponder = isFirstResponder
            self.placeholder = placeholder
        }
     
        func textViewDidChange(_ textView: UITextView) {
            self.text = textView.text
        }
        
        
        func textViewDidBeginEditing(_ textView: UITextView) {

            if textView.textColor == UIColor.lightGray {
                print(placeholder)
                textView.text = nil
                textView.textColor = UIColor.black
            }
        }

        func textViewDidEndEditing(_ textView: UITextView) {

            if textView.text.isEmpty {
                textView.text = placeholder
                textView.textColor = UIColor.lightGray
            } else {
                self.text = textView.text
            }
        }
    }
}

Answer 1

UITextView本身沒有占位符屬性，因此您必須使用自己的方法以編程方式創建和操作一個。 我建議使用以下任一解決方案，這取決於所需的行為。

解決方案：所以一種方法是，我將文本設置為gray ，並將其設置為默認值。 然后我創建了一個變量didStartEditing來檢查，如果用戶點擊textView ，占位符將被刪除。

所以這是我剛剛做的一個例子，你可以把它改成適合你的需要：

首先這是TextView結構。

struct TextView: UIViewRepresentable {

@Binding var text: String
@Binding var didStartEditing: Bool


func makeUIView(context: Context) -> UITextView {
    let textView = UITextView()
    
    textView.font = UIFont.preferredFont(forTextStyle: .body)
    textView.autocapitalizationType = .sentences
    textView.isSelectable = true
    textView.isUserInteractionEnabled = true
    
    return textView
}


func updateUIView(_ uiView: UITextView, context: Context) {
    
    if didStartEditing {
        
        uiView.textColor = UIColor.black
        uiView.text = text
        
    }
    else {
        uiView.text = "This is a place holder"
        uiView.textColor = UIColor.lightGray
    }
    
    uiView.font = UIFont.preferredFont(forTextStyle: .body)
    
}
} 

然后這是 SwiftUI 代碼：

@State var text = ""
@State var didStartEditing = false

var body: some View {
    TextView(text: $text, didStartEditing: $didStartEditing)
        .onTapGesture {
            didStartEditing = true
        }
}

您要求的結果：