Add support for iOS UndoManager #98294
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| // Copyright 2014 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
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| // Flutter code sample for UndoHistoryController. | ||
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| import 'package:flutter/material.dart'; | ||
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| void main() { | ||
| runApp(const MyApp()); | ||
| } | ||
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| class MyApp extends StatelessWidget { | ||
| const MyApp({super.key}); | ||
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| static const String _title = 'Flutter Code Sample'; | ||
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| @override | ||
| Widget build(BuildContext context) { | ||
| return const MaterialApp( | ||
| title: _title, | ||
| home: MyHomePage(), | ||
| ); | ||
| } | ||
| } | ||
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| class MyHomePage extends StatefulWidget { | ||
| const MyHomePage({super.key}); | ||
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| @override | ||
| State<MyHomePage> createState() => _MyHomePageState(); | ||
| } | ||
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| class _MyHomePageState extends State<MyHomePage> { | ||
| final TextEditingController _controller = TextEditingController(); | ||
| final FocusNode _focusNode = FocusNode(); | ||
| final UndoHistoryController _undoController = UndoHistoryController(); | ||
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| TextStyle? get enabledStyle => Theme.of(context).textTheme.bodyMedium; | ||
| TextStyle? get disabledStyle => Theme.of(context).textTheme.bodyMedium?.copyWith(color: Colors.grey); | ||
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| @override | ||
| Widget build(BuildContext context) { | ||
| return Scaffold( | ||
| body: Center( | ||
| child: Column( | ||
| mainAxisAlignment: MainAxisAlignment.center, | ||
| children: <Widget>[ | ||
| TextField( | ||
| maxLines: 4, | ||
| controller: _controller, | ||
| focusNode: _focusNode, | ||
| undoController: _undoController, | ||
| ), | ||
| ValueListenableBuilder<UndoHistoryValue>( | ||
| valueListenable: _undoController, | ||
| builder: (BuildContext context, UndoHistoryValue value, Widget? child) { | ||
| return Row( | ||
| children: <Widget>[ | ||
| TextButton( | ||
| child: Text('Undo', style: value.canUndo ? enabledStyle : disabledStyle), | ||
| onPressed: () { | ||
| _undoController.undo(); | ||
| }, | ||
| ), | ||
| TextButton( | ||
| child: Text('Redo', style: value.canRedo ? enabledStyle : disabledStyle), | ||
| onPressed: () { | ||
| _undoController.redo(); | ||
| }, | ||
| ), | ||
| ], | ||
| ); | ||
| }, | ||
| ), | ||
| ], | ||
| ), | ||
| ), | ||
| ); | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,131 @@ | ||
| // Copyright 2014 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
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| import 'package:flutter/foundation.dart'; | ||
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| import '../../services.dart'; | ||
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| /// The direction in which an undo action should be performed, whether undo or redo. | ||
| enum UndoDirection { | ||
| /// Perform an undo action. | ||
| undo, | ||
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| /// Perform a redo action. | ||
| redo | ||
| } | ||
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| /// A low-level interface to the system's undo manager. | ||
| /// | ||
| /// To receive events from the system undo manager, create an | ||
| /// [UndoManagerClient] and set it as the [client] on [UndoManager]. | ||
| /// | ||
| /// The [setUndoState] method can be used to update the system's undo manager | ||
| /// using the [canUndo] and [canRedo] parameters. | ||
| /// | ||
| /// When the system undo or redo button is tapped, the current | ||
| /// [UndoManagerClient] will receive [UndoManagerClient.handlePlatformUndo] | ||
| /// with an [UndoDirection] representing whether the event is "undo" or "redo". | ||
| /// | ||
| /// Currently, only iOS has an UndoManagerPlugin implemented on the engine side. | ||
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Contributor
There was a problem hiding this comment. Nit: Maybe add the following. I'm looking at these docs and noticing that someone that lands on this page might not know what this class can actually be used for at a high level. "On iOS, this can be used to listen to the keyboard undo/redo buttons and the undo/redo gestures."
Contributor
There was a problem hiding this comment. Do we have an issue to also add support for macos?
Contributor
Author
There was a problem hiding this comment. Someone else should double check me on this, but it seems to work on macOS without any further changes, I think because we're handling the UndoTextIntent and RedoTextIntent.
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| /// On iOS, this can be used to listen to the keyboard undo/redo buttons and the | ||
| /// undo/redo gestures. | ||
| /// | ||
| /// See also: | ||
| /// | ||
| /// * [NSUndoManager](https://developer.apple.com/documentation/foundation/nsundomanager) | ||
| class UndoManager { | ||
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| UndoManager._() { | ||
| _channel = SystemChannels.undoManager; | ||
| _channel.setMethodCallHandler(_handleUndoManagerInvocation); | ||
| } | ||
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| /// Set the [MethodChannel] used to communicate with the system's undo manager. | ||
| /// | ||
| /// This is only meant for testing within the Flutter SDK. Changing this | ||
| /// will break the ability to set the undo status or receive undo and redo | ||
| /// events from the system. This has no effect if asserts are disabled. | ||
| @visibleForTesting | ||
| static void setChannel(MethodChannel newChannel) { | ||
| assert(() { | ||
| _instance._channel = newChannel..setMethodCallHandler(_instance._handleUndoManagerInvocation); | ||
| return true; | ||
| }()); | ||
| } | ||
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| static final UndoManager _instance = UndoManager._(); | ||
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| /// Receive undo and redo events from the system's [UndoManager]. | ||
| /// | ||
| /// Setting the [client] will cause [UndoManagerClient.handlePlatformUndo] | ||
| /// to be called when a system undo or redo is triggered, such as by tapping | ||
| /// the undo/redo keyboard buttons or using the 3-finger swipe gestures. | ||
| static set client(UndoManagerClient? client) { | ||
| _instance._currentClient = client; | ||
| } | ||
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| /// Return the current [UndoManagerClient]. | ||
| static UndoManagerClient? get client => _instance._currentClient; | ||
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| /// Set the current state of the system UndoManager. [canUndo] and [canRedo] | ||
| /// control the respective "undo" and "redo" buttons of the system UndoManager. | ||
| static void setUndoState({bool canUndo = false, bool canRedo = false}) { | ||
| _instance._setUndoState(canUndo: canUndo, canRedo: canRedo); | ||
| } | ||
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| late MethodChannel _channel; | ||
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| UndoManagerClient? _currentClient; | ||
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| Future<dynamic> _handleUndoManagerInvocation(MethodCall methodCall) async { | ||
| final String method = methodCall.method; | ||
| final List<dynamic> args = methodCall.arguments as List<dynamic>; | ||
| if (method == 'UndoManagerClient.handleUndo') { | ||
| assert(_currentClient != null, 'There must be a current UndoManagerClient.'); | ||
| _currentClient!.handlePlatformUndo(_toUndoDirection(args[0] as String)); | ||
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| return; | ||
| } | ||
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| throw MissingPluginException(); | ||
| } | ||
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| void _setUndoState({bool canUndo = false, bool canRedo = false}) { | ||
| _channel.invokeMethod<void>( | ||
| 'UndoManager.setUndoState', | ||
| <String, bool>{'canUndo': canUndo, 'canRedo': canRedo} | ||
| ); | ||
| } | ||
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| UndoDirection _toUndoDirection(String direction) { | ||
| switch (direction) { | ||
| case 'undo': | ||
| return UndoDirection.undo; | ||
| case 'redo': | ||
| return UndoDirection.redo; | ||
| } | ||
| throw FlutterError.fromParts(<DiagnosticsNode>[ErrorSummary('Unknown undo direction: $direction')]); | ||
| } | ||
| } | ||
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| /// An interface to receive events from a native UndoManager. | ||
| mixin UndoManagerClient { | ||
| /// Requests that the client perform an undo or redo operation. | ||
| /// | ||
| /// Currently only used on iOS 9+ when the undo or redo methods are invoked | ||
| /// by the platform. For example, when using three-finger swipe gestures, | ||
| /// the iPad keyboard, or voice control. | ||
| void handlePlatformUndo(UndoDirection direction); | ||
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| /// Reverts the value on the stack to the previous value. | ||
| void undo(); | ||
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| /// Updates the value on the stack to the next value. | ||
| void redo(); | ||
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| /// Will be true if there are past values on the stack. | ||
| bool get canUndo; | ||
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| /// Will be true if there are future values on the stack. | ||
| bool get canRedo; | ||
| } | ||
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Thanks for adding a full example! Even just for me as a reviewer it helps me understand this PR.