Navigator operation requested with a context that does not include a Navigator

103
votes

I'm trying to start a new screen within an onTap but I get the following error:

Navigator operation requested with a context that does not include a Navigator.

The code I am using to navigate is:

onTap: () { Navigator.of(context).pushNamed('/settings'); },

I have set up a route in my app as follows:

routes: <String, WidgetBuilder>{
    '/settings': (BuildContext context) => new SettingsPage(),
},

I've tried to copy the code using the stocks sample application. I've looked at the Navigator and Route documentation and can't figure out how the context can be made to include a Navigator. The context being used in the onTap is referenced from the parameter passed into the build method:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {

SettingsPage is a class as follows:

class SettingsPage extends Navigator {

Widget buildAppBar(BuildContext context) {
  return new AppBar(
    title: const Text('Settings')
  );
}

@override
Widget build(BuildContext context) {
  return new Scaffold(
    appBar: buildAppBar(context),
  );
 }
}
13
flutter

13 Answers

253
votes

TLDR: Wrap the widget which needs to access to Navigator into a Builder or extract that sub-tree into a class. And use the new BuildContext to access Navigator.

This error is unrelated to the destination. It happens because you used a context that doesn't contain a Navigator instance as parent.

How do I create a Navigator instance then ?

This is usually done by inserting in your widget tree a MaterialApp or WidgetApp. Although you can do it manually by using Navigator directly but less recommended. Then, all children of such widget can access NavigatorState using Navigator.of(context).

Wait, I already have a MaterialApp/WidgetApp !

That's most likely the case. But this error can still happens when you use a context that is a parent of MaterialApp/WidgetApp.

This happens because when you do Navigator.of(context), it will start from the widget associated to the context used. And then go upward in the widget tree until it either find a Navigator or there's no more widget.

In the first case, everything is fine. In the second, it throws a

Navigator operation requested with a context that does not include a Navigator.

So, how do I fix it ?

First, let's reproduce this error :

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Center(
        child: RaisedButton(
          child: Text("Foo"),
          onPressed: () => Navigator.pushNamed(context, "/"),
        ),
      ),
    );
  }
}

This example creates a button that attempts to go to '/' on click but will instead throw an exception.

Notice here that in the 

  onPressed: () => Navigator.pushNamed(context, "/"),

we used context passed by to build of MyApp.

The problem is, MyApp is actually a parent of MaterialApp. As it's the widget who instantiate MaterialApp! Therefore MyApp's BuildContext doesn't have a MaterialApp as parent!

To solve this problem, we need to use a different context.

In this situation, the easiest solution is to introduce a new widget as child of MaterialApp. And then use that widget's context to do the Navigator call.

There are a few ways to achieve this. You can extract home into a custom class :

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHome()
    );
  }
}

class MyHome extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
        child: RaisedButton(
          child: Text("Foo"),
          onPressed: () => Navigator.pushNamed(context, "/"),
        ),
      );
  }
}

Or you can use Builder :

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Builder(
        builder: (context) => Center(
              child: RaisedButton(
                child: Text("Foo"),
                onPressed: () => Navigator.pushNamed(context, "/"),
              ),
            ),
      ),
    );
  }
}
23
votes

Hy guys, i have the same problem. This is occur for me. The solution what i found is very simple. Only what i did is in a simple code:

void main() {
  runApp(MaterialApp(
    home: YOURAPP() ,
    ),
  );
}

I hope was useful.

17
votes

Make sure your current parent widget not with same level with MaterialApp

Wrong Way 

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          centerTitle: true,
          title: Text('Title'),
        ),
        body: Center(
            child: Padding(
          padding: EdgeInsets.symmetric(vertical: 8.0, horizontal: 16.0),
          child: RaisedButton(
              onPressed: () {
                //wrong way: use context in same level tree with MaterialApp
                Navigator.push(context,
                    MaterialPageRoute(builder: (context) => ScanScreen()));
              },
              child: const Text('SCAN')),
        )),
      ),
    );
  }
}

Right way

void main() => runApp(MaterialApp(
      title: "App",
      home: HomeScreen(),
    ));

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: Text('Title'),
      ),
      body: Center(
          child: Padding(
        padding: EdgeInsets.symmetric(vertical: 8.0, horizontal: 16.0),
        child: RaisedButton(
            onPressed: () {
            //right way: use context in below level tree with MaterialApp
              Navigator.push(context,
                  MaterialPageRoute(builder: (context) => ScanScreen()));
            },
            child: const Text('SCAN')),
      )),
    );
  }
}
13
votes

I set up this simple example for routing in a flutter app:

import 'package:flutter/material.dart';

void main() {
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      home: new MyHomePage(),
      routes: <String, WidgetBuilder>{
        '/settings': (BuildContext context) => new SettingsPage(),
      },
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('TestProject'),
      ),
      body: new Center(
        child: new FlatButton(
          child: const Text('Go to Settings'),
          onPressed: () => Navigator.of(context).pushNamed('/settings')
        )
      )
    );
  }
}

class SettingsPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('SettingsPage'),
        ),
        body: new Center(
            child: new Text('Settings')
        )
    );
  }
}

Note, that the SettingsPage extends StatelessWidget and not Navigator. I'm not able to reproduce your error.

Does this example help you in building your app? Let me know if I can help you with anything else.

9
votes

You should rewrite your code in main.dart FROM: 

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

TO

void main() {
  runApp(MaterialApp(
  title: 'Your title',
  home: MyApp(),));}

The point is to have the home property to be your first page this worked for me, I hope it will help someone in the future

7
votes

Just like with a Scaffold you can use a GlobalKey. It doesn't need context.

final _navKey = GlobalKey<NavigatorState>();

void _navigateToLogin() {
  _navKey.currentState.popUntil((r) => r.isFirst);
  _navKey.currentState.pushReplacementNamed(LoginRoute.name);
}

@override
Widget build(BuildContext context) {
  return MaterialApp(
    navigatorKey: _navKey,
    ...
  );
}
4
votes

A complete and tested solution:

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:my-app/view/main-view.dart';

class SplashView extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        home: Builder(
          builder: (context) => new _SplashContent(),
        ),
        routes: <String, WidgetBuilder>{
          '/main': (BuildContext context) => new MainView()}
    );
  }
}

class _SplashContent extends StatefulWidget{

  @override
  _SplashContentState createState() => new _SplashContentState();
}

class _SplashContentState extends State<_SplashContent>
    with SingleTickerProviderStateMixin {

  var _iconAnimationController;
  var _iconAnimation;

  startTimeout() async {
    var duration = const Duration(seconds: 3);
    return new Timer(duration, handleTimeout);
  }

  void handleTimeout() {
    Navigator.pushReplacementNamed(context, "/main");
  }

  @override
  void initState() {
    super.initState();

    _iconAnimationController = new AnimationController(
        vsync: this, duration: new Duration(milliseconds: 2000));

    _iconAnimation = new CurvedAnimation(
        parent: _iconAnimationController, curve: Curves.easeIn);
    _iconAnimation.addListener(() => this.setState(() {}));

    _iconAnimationController.forward();

    startTimeout();
  }

  @override
  Widget build(BuildContext context) {
    return new Center(
        child: new Image(
          image: new AssetImage("images/logo.png"),
          width: _iconAnimation.value * 100,
          height: _iconAnimation.value * 100,
        )
    );
  }
}
2
votes

I was facing the same problem and solved by removing home from MaterialApp and use initialRoute instead.

return MaterialApp(
      debugShowCheckedModeBanner: false,
      initialRoute: '/',
      routes: {
        '/': (context) => MyApp(),
        '/settings': (context) => SettingsPage(),
      },
    );

And

onTap: () => {
               Navigator.pushNamed(context, "/settings")
                },
1
votes

It happens because the context on the widget that tries to navigate is still using the material widget.

The short answer for the solution is to :

extract your widget

that has navigation to new class so it has a different context when calling the navigation

1
votes

Change your main function example:

`void main() {
  runApp(MaterialApp(
  title: 'Your title',
  home: MyApp(),));}`
0
votes

When your screen is not navigated from other screen,you don't initially have access to the navigator,Because it is not instantiated yet.So in that case wrap your widget with builder and extract context from there.This worked for me.

builder: (context) => Center(
              child: RaisedButton(
                child: Text("Foo"),
                onPressed: () => Navigator.pushNamed(context, "/"),
              ),
0
votes

You ca use this plugin https://pub.dev/packages/get/versions/2.0.2

in The MaterialApp assign property navigatorKey: Get.key,

MaterialApp(
      navigatorKey: Get.key,
      initialRoute: "/",
     );

you can access Get.toNamed("Your route name");

0
votes

As per this comment If your navigator is inside Material context navigator push will give this error. if you create a new widget and assign it to the material app home navigator will work.

This won't work

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text("Title"),
        ),
        body: new Center(child: new Text("Click Me")),
        floatingActionButton: new FloatingActionButton(
          child: new Icon(Icons.add),
          backgroundColor: Colors.orange,
          onPressed: () {
            print("Clicked");
            Navigator.push(
              context,
              new MaterialPageRoute(builder: (context) => new AddTaskScreen()),
            );
          },
        ),
      ),
    );
  }
}

This will work

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        home: new HomeScreen());
  }
}

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Title"),
      ),
      body: new Center(child: new Text("Click Me")),
      floatingActionButton: new FloatingActionButton(
        child: new Icon(Icons.add),
        backgroundColor: Colors.orange,
        onPressed: () {
          print("Clicked");
          Navigator.push(
            context,
            new MaterialPageRoute(builder: (context) => new AddTaskScreen()),
          );
        },
      ),
    );
  }
}