在SwiftUI中向UITextView添加占位符(UIViewRepresentable)

import SwiftUI

struct TextView: UIViewRepresentable {
    @Binding var text: String
    var placeholder: String

    func makeUIView(context: Context) -> UITextView {
        let textView = UITextView()
        textView.delegate = context.coordinator
        textView.font = UIFont.preferredFont(forTextStyle: .body)
        textView.isScrollEnabled = true
        textView.isEditable = true
        textView.isUserInteractionEnabled = true
        textView.backgroundColor = UIColor.clear
        textView.text = placeholder
        textView.textColor = UIColor.lightGray
        return textView
    }

    func updateUIView(_ uiView: UITextView, context: Context) {
        if uiView.text != text {
            uiView.text = text
        }
    }

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

    class Coordinator: NSObject, UITextViewDelegate {
        var parent: TextView

        init(_ textView: TextView) {
            self.parent = textView
        }

        func textViewDidChange(_ textView: UITextView) {
            self.parent.text = textView.text
        }

        func textViewDidBeginEditing(_ textView: UITextView) {
            if textView.textColor == UIColor.lightGray {
                textView.text = nil
                textView.textColor = UIColor.black
            }
        }

        func textViewDidEndEditing(_ textView: UITextView) {
            if textView.text.isEmpty {
                textView.text = parent.placeholder
                textView.textColor = UIColor.lightGray
            }
        }
    }
}

struct ContentView: View {
    @State private var text = ""

    var body: some View {
        VStack {
            TextView(text: $text, placeholder: "请输入文本")
                .frame(height: 200)
                .padding()
        }
    }
}