Open drawer on clicking AppBar

Question

If you create an Scafold there is an option for drawer. If you now create this drawer you get automaticly the menu icon on the leading position of the appbar. But i want an

Answer 1

you need initialize scaffoldKey after that,

Open drawer and close drawer

 GestureDetector(
          onTap: () {
            if(scaffoldKey.currentState.isDrawerOpen){
              scaffoldKey.currentState.openEndDrawer();
            }else{
              scaffoldKey.currentState.openDrawer();
            }
          },
          child:  LeadingIcon(icon: Icons.menu),//your button
        ),

Answer 2

Use a Key in your Scaffold and show the drawer by calling myKey.currentState.openDrawer(), here is a working code:

import "package:flutter/material.dart";

class Test extends StatefulWidget {
  @override
  _TestState createState() => new _TestState();
}

class _TestState extends State<Test> {
  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: _scaffoldKey,
      drawer: new Drawer(),
      appBar: new AppBar(
        leading: new IconButton(
          icon: new Icon(Icons.settings),
          onPressed: () => _scaffoldKey.currentState.openDrawer(),
        ),
      ),
    );
  }
}

Answer 3

Alternative to the accepted answer which does not require a GlobalKey:

class _TestState extends State<Test> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      drawer: new Drawer(),
      appBar: new AppBar(
        leading: Builder(
        builder: (context) => IconButton(
            icon: new Icon(Icons.settings),
            onPressed: () => Scaffold.of(context).openDrawer(),
          ),
        ),
      ),
    );
  }
}