Simple custom drawer

main.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import 'counter.dart';

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

class MyModel extends ChangeNotifier {
  bool isDrawerOpened = false;

  void toggleDrawer() {
    isDrawerOpened = !isDrawerOpened;
    notifyListeners();
  }
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<MyModel>(
      create: (_) => MyModel(),
      child: MaterialApp(
        title: 'Flutter Demo',
        home: CounterPage(title: 'Flutter Demo Home Page'),
      ),
    );
  }
}

class CounterPage extends StatefulWidget {
  final String title;
  CounterPage({Key key, this.title}) : super(key: key);

  @override
  _CounterPageState createState() => _CounterPageState();
}

class _CounterPageState extends State<CounterPage> {
  Counter counter = Counter(0);

  Widget _buildDrawer(bool show) {
    return AnimatedContainer(
      duration: Duration(milliseconds: 300),
      curve: Curves.easeOutExpo,
      color: Colors.red,
      height: MediaQuery.of(context).size.height,
      width: show ? MediaQuery.of(context).size.width / 1.3 : 0,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Consumer<MyModel>(
      builder: (context, model, child) => Stack(
        children: <Widget>[
          child,
          _buildDrawer(model.isDrawerOpened),
        ],
      ),
      child: Scaffold(
        appBar: AppBar(title: Text(widget.title)),
        body: Center(child: Text('Widget')),
        floatingActionButton: Row(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            FloatingActionButton(
              child: Icon(Icons.add),
              onPressed: () {
                Provider.of<MyModel>(context, listen: false).toggleDrawer();
              },
            ),
          ],
        ),
      ),
    );
  }
}