Shortcuts class Null safety

A widget to that creates key bindings to specific actions for its descendants.

This widget establishes a ShortcutManager to be used by its descendants when invoking an Action via a keyboard key combination that maps to an Intent.

Here, we will use the Shortcuts and Actions widgets to add and subtract from a counter. When the child widget has keyboard focus, and a user presses the keys that have been defined in Shortcuts, the action that is bound to the appropriate Intent for the key is invoked.

It also shows the use of a CallbackAction to avoid creating a new Action subclass.

To create a local project with this code sample, run:
flutter create --sample=widgets.Shortcuts.1 mysample

It also shows the use of a CallbackAction to avoid creating a new Action subclass.

import 'package:flutter/services.dart';

// ...

class IncrementIntent extends Intent {
  const IncrementIntent();
}

class DecrementIntent extends Intent {
  const DecrementIntent();
}

// ...

int count = 0;

@override
Widget build(BuildContext context) {
  return Shortcuts(
    shortcuts: <LogicalKeySet, Intent>{
      LogicalKeySet(LogicalKeyboardKey.arrowUp): const IncrementIntent(),
      LogicalKeySet(LogicalKeyboardKey.arrowDown): const DecrementIntent(),
    },
    child: Actions(
      actions: <Type, Action<Intent>>{
        IncrementIntent: CallbackAction<IncrementIntent>(
          onInvoke: (IncrementIntent intent) => setState(() {
            count = count + 1;
          }),
        ),
        DecrementIntent: CallbackAction<DecrementIntent>(
          onInvoke: (DecrementIntent intent) => setState(() {
            count = count - 1;
          }),
        ),
      },
      child: Focus(
        autofocus: true,
        child: Column(
          children: <Widget>[
            const Text('Add to the counter by pressing the up arrow key'),
            const Text(
                'Subtract from the counter by pressing the down arrow key'),
            Text('count: $count'),
          ],
        ),
      ),
    ),
  );
}

This slightly more complicated, but more flexible, example creates a custom Action subclass to increment and decrement within a widget (a Column) that has keyboard focus. When the user presses the up and down arrow keys, the counter will increment and decrement a data model using the custom actions.

One thing that this demonstrates is passing arguments to the Intent to be carried to the Action. This shows how actions can get data either from their own construction (like the model in this example), or from the intent passed to them when invoked (like the increment amount in this example).

To create a local project with this code sample, run:
flutter create --sample=widgets.Shortcuts.2 mysample

import 'package:flutter/services.dart';

// ...

class Model with ChangeNotifier {
  int count = 0;
  void incrementBy(int amount) {
    count += amount;
    notifyListeners();
  }

  void decrementBy(int amount) {
    count -= amount;
    notifyListeners();
  }
}

class IncrementIntent extends Intent {
  const IncrementIntent(this.amount);

  final int amount;
}

class DecrementIntent extends Intent {
  const DecrementIntent(this.amount);

  final int amount;
}

class IncrementAction extends Action<IncrementIntent> {
  IncrementAction(this.model);

  final Model model;

  @override
  void invoke(covariant IncrementIntent intent) {
    model.incrementBy(intent.amount);
  }
}

class DecrementAction extends Action<DecrementIntent> {
  DecrementAction(this.model);

  final Model model;

  @override
  void invoke(covariant DecrementIntent intent) {
    model.decrementBy(intent.amount);
  }
}

// ...

Model model = Model();

@override
Widget build(BuildContext context) {
  return Shortcuts(
    shortcuts: <LogicalKeySet, Intent>{
      LogicalKeySet(LogicalKeyboardKey.arrowUp): const IncrementIntent(2),
      LogicalKeySet(LogicalKeyboardKey.arrowDown): const DecrementIntent(2),
    },
    child: Actions(
      actions: <Type, Action<Intent>>{
        IncrementIntent: IncrementAction(model),
        DecrementIntent: DecrementAction(model),
      },
      child: Focus(
        autofocus: true,
        child: Column(
          children: <Widget>[
            const Text('Add to the counter by pressing the up arrow key'),
            const Text(
                'Subtract from the counter by pressing the down arrow key'),
            AnimatedBuilder(
              animation: model,
              builder: (BuildContext context, Widget? child) {
                return Text('count: ${model.count}');
              },
            ),
          ],
        ),
      ),
    ),
  );
}

Constructors

Shortcuts({Key? key, ShortcutManager? manager, required Map<LogicalKeySet, Intent> shortcuts, required Widget child, String? debugLabel}): Creates a const Shortcuts widget. [...]
const

Properties

child → Widget: The child widget for this Shortcuts widget. [...]
final
debugLabel → String?: The debug label that is printed for this node when logged. [...]
final
hashCode → int: The hash code for this object. [...]
@nonVirtual, read-only, inherited
key → Key?: Controls how one widget replaces another widget in the tree. [...]
final, inherited
manager → ShortcutManager?: The ShortcutManager that will manage the mapping between key combinations and Actions. [...]
final
runtimeType → Type: A representation of the runtime type of the object.
read-only, inherited
shortcuts → Map<LogicalKeySet, Intent>: The map of shortcuts that the ShortcutManager will be given to manage. [...]
final

Methods

createElement() → StatefulElement: Creates a StatefulElement to manage this widget's location in the tree. [...]
inherited
createState() → _ShortcutsState: Creates the mutable state for this widget at a given location in the tree. [...]
override
debugDescribeChildren() → List<DiagnosticsNode>: Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void: Add additional properties associated with the node. [...]
override
noSuchMethod(Invocation invocation) → dynamic: Invoked when a non-existent method or property is accessed. [...]
inherited
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode: Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel: DiagnosticLevel.info}) → String: A string representation of this object. [...]
inherited
toStringDeep({String prefixLineOne: '', String? prefixOtherLines, DiagnosticLevel minLevel: DiagnosticLevel.debug}) → String: Returns a string representation of this node and its descendants. [...]
inherited
toStringShallow({String joiner: ', ', DiagnosticLevel minLevel: DiagnosticLevel.debug}) → String: Returns a one-line detailed description of the object. [...]
inherited
toStringShort() → String: A short, textual description of this widget.
inherited

Operators

operator ==(Object other) → bool: The equality operator. [...]
@nonVirtual, inherited

Static Methods

maybeOf(BuildContext context) → ShortcutManager?: Returns the ShortcutManager that most tightly encloses the given BuildContext. [...]
of(BuildContext context) → ShortcutManager: Returns the ShortcutManager that most tightly encloses the given BuildContext. [...]