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Description:

undo

undo #

An undo redo library for Dart/Flutter. Forked from here and updated for Flutter. Demo can be viewed here.
Usage #
Create an ChangeStack to store changes
import 'package:undo/undo.dart';

var changes = new ChangeStack();
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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.
var count = 0;

changes.add(
new Change(count, () => count++, (val) => count = val);
name: "Increase"
);
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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.
var person = new Person()
..firstName = "John"
..lastName = "Doe";

changes.add(
new Change(
person.firstName,
() => person.firstName = "Jane",
(oldValue) = person.firstName = oldValue
)
)
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Undo a change with undo().
print(person.firstName); // Jane
changes.undo();
print(person.firstName); // John
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Redo the change with redo().
changes.redo();
print(person.firstName); // Jane
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Simple Stack Example #

class HomeScreen extends StatefulWidget {
@override
_HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
SimpleStack _controller;

@override
void initState() {
_controller = SimpleStack<int>(
0,
onUpdate: (val) {
if (mounted)
setState(() {
print('New Value -> $val');
});
},
);
super.initState();
}

@override
Widget build(BuildContext context) {
final count = _controller.state;
return Scaffold(
appBar: AppBar(
title: Text('Undo/Redo Example'),
),
body: Center(
child: Text('Count: $count'),
),
bottomNavigationBar: BottomAppBar(
child: Row(
children: <Widget>[
IconButton(
icon: Icon(Icons.arrow_back),
onPressed: !_controller.canUndo
? null
: () {
if (mounted)
setState(() {
_controller.undo();
});
},
),
IconButton(
icon: Icon(Icons.arrow_forward),
onPressed: !_controller.canRedo
? null
: () {
if (mounted)
setState(() {
_controller.redo();
});
},
),
],
),
),
floatingActionButtonLocation: FloatingActionButtonLocation.endDocked,
floatingActionButton: FloatingActionButton(
heroTag: ValueKey('add_button'),
child: Icon(Icons.add),
onPressed: () {
_controller.modify(count + 1);
},
),
);
}
}

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