Actions

sample.packages.flutter.lib.src.widgets.actions.391.

This example shows how ActionListener handles adding and removing of the [listener] in the widget lifecycle.

  
import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: const Center(
          child: MyStatefulWidget(),
        ),
      ),
    );
  }
}

class ActionListenerExample extends StatefulWidget {
  const ActionListenerExample({Key? key}) : super(key: key);

  @override
  State createState() => _ActionListenerExampleState();
}

class _ActionListenerExampleState extends State {
  bool _on = false;
  late final MyAction _myAction;

  @override
  void initState() {
    super.initState();
    _myAction = MyAction();
  }

  void _toggleState() {
    setState(() {
      _on = !_on;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Padding(
          padding: const EdgeInsets.all(8.0),
          child: OutlinedButton(
            onPressed: _toggleState,
            child: Text(_on ? 'Disable' : 'Enable'),
          ),
        ),
        if (_on)
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: ActionListener(
              listener: (Action action) {
                if (action.intentType == MyIntent) {
                  ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
                    content: Text('Action Listener Called'),
                  ));
                }
              },
              action: _myAction,
              child: ElevatedButton(
                onPressed: () => const ActionDispatcher()
                    .invokeAction(_myAction, const MyIntent()),
                child: const Text('Call Action Listener'),
              ),
            ),
          ),
        if (!_on) Container(),
      ],
    );
  }
}

class MyAction extends Action {
  @override
  void addActionListener(ActionListenerCallback listener) {
    super.addActionListener(listener);
    debugPrint('Action Listener was added');
  }

  @override
  void removeActionListener(ActionListenerCallback listener) {
    super.removeActionListener(listener);
    debugPrint('Action Listener was removed');
  }

  @override
  void invoke(covariant MyIntent intent) {
    notifyActionListeners();
  }
}

class MyIntent extends Intent {
  const MyIntent();
}

class MyStatefulWidget extends StatefulWidget {
  const MyStatefulWidget({Key? key}) : super(key: key);

  @override
  State createState() => _MyStatefulWidgetState();
}

class _MyStatefulWidgetState extends State {
  @override
  Widget build(BuildContext context) {
    return const ActionListenerExample();
  }
}