lifecycle.dart

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/widgets.dart';

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

  @override
  _LifecycleWatcherState createState() => new _LifecycleWatcherState();
}

class _LifecycleWatcherState extends State<LifecycleWatcher>
                             with WidgetsBindingObserver {
  AppLifecycleState _lastLifecycleState;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    setState(() {
      _lastLifecycleState = state;
    });
  }

  @override
  Widget build(BuildContext context) {
    if (_lastLifecycleState == null)
      return const Text('This widget has not observed any lifecycle changes.');
    return new Text('The most recent lifecycle state this widget observed was: $_lastLifecycleState.');
  }
}


void main() {
  runApp(
    const Directionality(
      textDirection: TextDirection.ltr,
      child: Center(
        child: LifecycleWatcher(),
      ),
    ),
  );
}