Is it possible to pass AppBar from body in Scaffold widget?

Question

I have a Scaffold widget with drawer . The screens I need to show in body have different AppBars (some of them have indicators for PageView , some of them are single paged, some have logo in it). So I do not pass any AppBar to my Scaffold but include it in widget I use in body . But there is no hamburger icon for drawer and it.

Is it possible to pass this AppBar from my body widget to the Scaffold containing it?

Or if there is a better way of widgets composition to solve this scenario I'd like to give it a try.

UPD

There is a nice way to show BottomSheet os SnackBar with

Scaffold.of(context)
    .showSnackBar(SnackBar(content: Text('Processing Data')));

Unfortunately it is not the case for AppBar .

Answer 1

It seems like you want a global Scaffold that stays the same when you switch pages. In that case you have to write your own logic to make the menu button appear:

import 'package:flutter/material.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      builder: (context, child) {
        // wrap a scaffold around the Navigator so that it is the same for all pages
        return Scaffold(
          body: AppScaffold(child: child),
          drawer: Drawer(),
        );
      },
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        leading: buildLeadingAction(context),
        title: Text('Home'),
      ),
    );
  }
}

/// Makes it easier to access the outer scaffold with the drawer from any context
class AppScaffold extends InheritedWidget {
  const AppScaffold({Key key, @required Widget child})
      : assert(child != null),
        super(key: key, child: child);

  /// nullable
  static ScaffoldState of(BuildContext context) {
    return context
        .ancestorInheritedElementForWidgetOfExactType(AppScaffold)
        ?.ancestorStateOfType(const TypeMatcher<ScaffoldState>());
  }

  @override
  bool updateShouldNotify(AppScaffold old) => false;
}

/// This is a simple method and not a widget
/// so that null can be returned if no AppScaffold with a drawer was found
Widget buildLeadingAction(BuildContext context) {
  final ScaffoldState appScaffold = AppScaffold.of(context);
  if (appScaffold != null && appScaffold.hasDrawer) {
    return IconButton(
      icon: const Icon(Icons.menu),
      onPressed: () => appScaffold.openDrawer(),
      tooltip: MaterialLocalizations.of(context).openAppDrawerTooltip,
    );
  } else {
    return null;
  }
}

Alternatively you can also place the Scaffold for the drawer inside of the page, and use a GlobalKey to access its ScaffoldState .