141 lines
3.6 KiB
Markdown
141 lines
3.6 KiB
Markdown
# undo
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[](https://www.buymeacoffee.com/rodydavis)
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[](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=WSH3GVC49GNNJ)
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[](https://github.com/rodydavis/undo)
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[](https://pub.dev/packages/undo)
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An undo redo library for Dart/Flutter. Forked from [here](https://github.com/Mixbook/undo.dart) and updated for Flutter. Demo can be viewed [here](https://rodydavis.github.io/undo/).
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## Usage
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Create an ChangeStack to store changes
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```dart
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import 'package:undo/undo.dart';
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var changes = ChangeStack();
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```
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Add new undo, redo commands using `ChangeStack.add()`. When a change is added, it calls the change's `execute()` method. Use `Change()` for simple inline changes.
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```dart
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var count = 0;
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changes.add(
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Change(count, () => count++, (val) => count = val);
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name: "Increase"
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);
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```
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Use `Change()` when changing a field on an object. This will store the field's old value so it can be reverted.
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```dart
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var person = new Person()
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..firstName = "John"
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..lastName = "Doe";
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changes.add(
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Change(
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person.firstName,
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() => person.firstName = "Jane",
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(oldValue) = person.firstName = oldValue
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)
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)
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```
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Undo a change with `undo()`.
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```dart
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print(person.firstName); // Jane
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changes.undo();
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print(person.firstName); // John
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```
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Redo the change with `redo()`.
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```dart
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changes.redo();
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print(person.firstName); // Jane
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```
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### Simple Stack Example
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```dart
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class HomeScreen extends StatefulWidget {
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@override
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_HomeScreenState createState() => _HomeScreenState();
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}
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class _HomeScreenState extends State<HomeScreen> {
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SimpleStack _controller;
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@override
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void initState() {
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_controller = SimpleStack<int>(
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0,
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onUpdate: (val) {
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if (mounted)
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setState(() {
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print('New Value -> $val');
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});
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},
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);
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super.initState();
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}
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@override
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Widget build(BuildContext context) {
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final count = _controller.state;
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return Scaffold(
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appBar: AppBar(
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title: Text('Undo/Redo Example'),
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),
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body: Center(
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child: Text('Count: $count'),
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),
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bottomNavigationBar: BottomAppBar(
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child: Row(
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children: <Widget>[
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IconButton(
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icon: Icon(Icons.arrow_back),
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onPressed: !_controller.canUndo
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? null
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: () {
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if (mounted)
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setState(() {
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_controller.undo();
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});
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},
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),
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IconButton(
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icon: Icon(Icons.arrow_forward),
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onPressed: !_controller.canRedo
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? null
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: () {
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if (mounted)
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setState(() {
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_controller.redo();
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});
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},
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),
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],
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),
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),
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floatingActionButtonLocation: FloatingActionButtonLocation.endDocked,
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floatingActionButton: FloatingActionButton(
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heroTag: ValueKey('add_button'),
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child: Icon(Icons.add),
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onPressed: () {
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_controller.modify(count + 1);
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},
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),
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);
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}
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}
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```
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