dlgchg · June 6, 2020 08:11 · Jun 6, 2020
diff --git a/MultilineTextField.swift b/MultilineTextField.swift
@@ -0,0 +1,140 @@
+//
+//  MultilineTextField.swift
+//  GipsyToDo
+//
+//  Created by liwei on 2020/6/4.
+//  Copyright © 2020 liwei. All rights reserved.
+//
+
+import Foundation
+import SwiftUI
+import UIKit
+
+struct MultilineTextField: View {
+
+    private var placeholder: String
+    private var onCommit: (() -> Void)?
+    @State private var viewHeight: CGFloat = 40 //start with one line
+    @State private var shouldShowPlaceholder = false
+    @Binding private var text: String
+    @Binding private var showKeyBoard: Bool
+
+    private var internalText: Binding<String> {
+        Binding<String>(get: { self.text } ) {
+            self.text = $0
+            self.shouldShowPlaceholder = $0.isEmpty
+        }
+    }
+
+    var body: some View {
+        UITextViewWrapper(text: self.internalText, showKeyBoard: $showKeyBoard, calculatedHeight: $viewHeight, onDone: onCommit)
+            .frame(minHeight: viewHeight, maxHeight: viewHeight)
+            .background(placeholderView, alignment: .topLeading)
+    }
+
+    var placeholderView: some View {
+        Group {
+            if shouldShowPlaceholder {
+                Text(placeholder).foregroundColor(.gray)
+                    .padding(.leading, 4)
+                    .padding(.top, 8)
+            }
+        }
+    }
+
+    init (_ placeholder: String = "", text: Binding<String>, showKeyBoard: Binding<Bool>, onCommit: (() -> Void)? = nil) {
+        self.placeholder = placeholder
+        self.onCommit = onCommit
+        self._text = text
+        self._showKeyBoard = showKeyBoard
+        self._shouldShowPlaceholder = State<Bool>(initialValue: self.text.isEmpty)
+    }
+
+}
+
+
+private struct UITextViewWrapper: UIViewRepresentable {
+    typealias UIViewType = UITextView
+
+    @Binding var text: String
+    @Binding var showKeyBoard: Bool
+    @Binding var calculatedHeight: CGFloat
+    var onDone: (() -> Void)?
+
+    func makeUIView(context: UIViewRepresentableContext<UITextViewWrapper>) -> UITextView {
+        let textField = UITextView()
+        textField.delegate = context.coordinator
+
+        textField.isEditable = true
+        textField.font = UIFont.preferredFont(forTextStyle: .body)
+        textField.isSelectable = true
+        textField.isUserInteractionEnabled = true
+        textField.isScrollEnabled = false
+        textField.backgroundColor = UIColor.clear
+
+
+        if nil != onDone {
+            textField.returnKeyType = .done
+        }
+
+        textField.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
+        return textField
+    }
+
+    func updateUIView(_ uiView: UITextView, context: UIViewRepresentableContext<UITextViewWrapper>) {
+        if uiView.text != self.text {
+            uiView.text = self.text
+        }
+        if self.showKeyBoard {
+            uiView.becomeFirstResponder()
+        } else {
+            uiView.resignFirstResponder()
+        }
+//        if uiView.window != nil, !uiView.isFirstResponder {
+//            uiView.becomeFirstResponder()
+//        }
+        UITextViewWrapper.recalculateHeight(view: uiView, result: $calculatedHeight)
+    }
+
+    private static func recalculateHeight(view: UIView, result: Binding<CGFloat>) {
+        let newSize = view.sizeThatFits(CGSize(width: view.frame.size.width, height: CGFloat.greatestFiniteMagnitude))
+        if result.wrappedValue != newSize.height {
+            DispatchQueue.main.async {
+                result.wrappedValue = newSize.height // call in next render cycle.
+            }
+        }
+    }
+
+    func makeCoordinator() -> Coordinator {
+        return Coordinator(text: $text, showKeyBoard: $showKeyBoard, height: $calculatedHeight, onDone: onDone)
+    }
+
+    final class Coordinator: NSObject, UITextViewDelegate {
+        var text: Binding<String>
+        var showKeyBoard: Binding<Bool>
+        var calculatedHeight: Binding<CGFloat>
+        var onDone: (() -> Void)?
+
+        init(text: Binding<String>,showKeyBoard: Binding<Bool>, height: Binding<CGFloat>, onDone: (() -> Void)? = nil) {
+            self.text = text
+            self.showKeyBoard = showKeyBoard
+            self.calculatedHeight = height
+            self.onDone = onDone
+        }
+
+        func textViewDidChange(_ uiView: UITextView) {
+            text.wrappedValue = uiView.text
+            UITextViewWrapper.recalculateHeight(view: uiView, result: calculatedHeight)
+        }
+
+        func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
+            if let onDone = self.onDone, text == "\n" {
+                textView.resignFirstResponder()
+                onDone()
+                return false
+            }
+            return true
+        }
+    }
+
+}