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

flutter 最容易报的一个错误就是does not include，因为其思想是组合

这种情况即使是外面包裹了materialapp也是无效的，因为flutter会根据这个context一直上溯，一直到根节点的widget，注意，上溯是根据context的，会上溯到这个context相关的widget的最根节点

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

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

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

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