how to open drawer in flutter in custom code example

Example 1: flutter drawer

Scaffold(
   drawer: Drawer(
      child: ListView(
        padding: EdgeInsets.zero,
        children: [
              DrawerHeader(
                   child: Text("Header")),
              ListTile(
                  title: Text("Home"))
        ]),
  ), 
);

Example 2: app drawer in flutter

Widget createDrawerHeader() {
 return DrawerHeader(
     margin: EdgeInsets.zero,
     padding: EdgeInsets.zero,
     decoration: BoxDecoration(
         image: DecorationImage(
             fit: BoxFit.fill,
             image:  AssetImage('images/bg_header.jpeg'))),
     child: Stack(children: [
       Positioned(
           bottom: 12.0,
           left: 16.0,
           child: Text("Welcome to Flutter",
               style: TextStyle(
                   color: Colors.white,
                   fontSize: 20.0,
                   fontWeight: FontWeight.w500))),
     ]));
}