How can I resolve this Flutter Navigator.push() error?-CodePudding

I am trying to move from one page to another via Navigator.push. Here is my code:

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int count = 0;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.deepOrange,
          title: const Text("Noice!"),
        ),

        body: ElevatedButton(
          child: const Text('About'),
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => AboutScreen(),
              ),
            );
          },
        ),

class AboutScreen extends StatelessWidget {
  const AboutScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
          backgroundColor: const Color.fromARGB(255, 0, 255, 8),
          title: const Text("Flutter ballert")),
    );
  }
}

The code compiles and I can access the app, but clicking the button leads to an error:

Exception has occurred.
FlutterError (Navigator operation requested with a context that does not include a Navigator.
The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.)

I know that in the offical docs the example for navigation is a tiny bit different. They dont return MaterialApp, instead they return Scaffold. Whats the difference between the two? Why should I return MaterialApp in the first place? And why doesnt it work with returning MaterialApp?

I dont know why this happens. I am new to flutter, so apologies if thats really trivial.

CodePudding user response：

EDIT: Duplicate of: Navigator operation requested with a context that does not include a Navigator

The problem is with the context. To fix this. Wrap your widget in a Builder() Class:

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int count = 0;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Builder(builder: (context) {
        return Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.deepOrange,
            title: const Text("Noice!"),
          ),
          body: ElevatedButton(
            child: const Text('About'),
            onPressed: () {
              Navigator.push(
                  context,
                  MaterialPageRoute(
                    builder: (context) => AboutScreen(),
                  ));
            },
          ),
        );
      }),
    );
  }
}

class AboutScreen extends StatelessWidget {
  const AboutScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
          backgroundColor: const Color.fromARGB(255, 0, 255, 8),
          title: const Text("Flutter ballert")),
    );
  }
}

Here is a YouTube video by the Google team explaining Builder

CodePudding user response：

You need to pass the context:

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int count = 0;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.deepOrange,
          title: const Text("Noice!"),
        ),
        body: ElevatedButton(
          child: const Text('About'),
          onPressed: () {
            Navigator.of(context).push(
              MaterialPageRoute(
                builder: (context) => AboutScreen(),
              ),
            );
          },
        ),
      ),
    );
  }
}

class AboutScreen extends StatelessWidget {
  const AboutScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
          backgroundColor: const Color.fromARGB(255, 0, 255, 8),
          title: const Text("Flutter ballert")),
    );
  }
}

Basically you did:

Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => AboutScreen(),
              ),
            );

But you need to do this:

Navigator.of(context).push(
              MaterialPageRoute(
                builder: (context) => AboutScreen(),
              ),
            );