How to update the drawer content only

Question

We are using a Drawer to display the "settings" state. I would like the user to be able to change a setting and see the result reflected in the drawer.

But when I call setState, it updates the parent window, not the Drawer state.

I want the user to be able to change notification from 'none' to 'phone' and see the reflected in the drawer state. But instead it always shows original value.

  @override
  Widget build(BuildContext context) {
    var key = GlobalKey<ScaffoldState>();
    return Scaffold(
      key: key,
      body: Text("Test Data"),
      bottomNavigationBar: NavBar(),
      drawer: Drawer( child: components( context ) ),
    );
  }

Widget components( context )
  {
    return ListView(
      children: <Widget>[
        ListTile( dense: true, leading: Icon(Icons.notifications), title: Text("Notifications"),
            trailing: DropdownButtonHideUnderline ( child: DropdownButton<String>(
              value: Settings.notifications.toString().split('.')[1],
              icon: Icon(Icons.expand_more),
              onChanged: (String newValue) {
                if ( 'none' == newValue )
                  Settings.notifications = Notifications.none;
                else if ( 'email' == newValue )
                  Settings.notifications = Notifications.email;
                else if ( 'phone' == newValue )
                  Settings.notifications = Notifications.phone;
                else
                  Settings.notifications = Notifications.both;
                setState(() {
                });
              },
              items: <String>['none','email','phone','both']
                  .map<DropdownMenuItem<String>>((String value) {
                return DropdownMenuItem<String>( value: value, child: Text(value), );
              }).toList(),
            ) ),),
          ],
        );
    }

Answer 1

Drawer is a Stateless widget in itself

Placing your widget code in a function won't provide it a seperate state. It's essentially a part of the Main Widget, so the setState() calls are under Main Widget.

Make a seperate StatefulWidget (say MyStatefulDrawer), and place your Drawer Widget Code over there, with Drawer class as the root widget.

Now, use MyStatefulDrawer in your main widget as such:

@override
  Widget build(BuildContext context) {
    var key = GlobalKey<ScaffoldState>();
    return Scaffold(
      key: key,
      body: Text("Test Data"),
      bottomNavigationBar: NavBar(),
      drawer: MyStatefulDrawer(context),
    );
  }

Now that your drawer is Stateful, you can setState() within it and it'd be rebuilt with the updated value.