我有两个屏幕的应用程序，我想通过按下按钮从第一个屏幕推送到第二个屏幕。

屏幕 1

import 'package:flutter/material.dart';
import './view/second_page.dart';

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

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new MainScreen();
  }
}

class MainScreen extends State<MyApp> {

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

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        home: new Scaffold(
            appBar: new AppBar(
                title: new Text("Title")
            ),
            body: new Center(
                child: new FlatButton(child: new Text("Second page"),
                    onPressed: () {
                      Navigator.push(context,
                          new MaterialPageRoute(
                              builder: (context) => new SecondPage()))
                    }
                )
            )
        )
    );
  }
}

屏幕 2

import 'package:flutter/material.dart';

class SecondPage extends StatefulWidget {

  @override
  State<StatefulWidget> createState() {
    return new SecondPageState();
  }
}


class SecondPageState extends State<SecondPage> {

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

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Title"),
      ),
      body: new Center(
        child: new Text("Some text"),
      ),
    );
  }
}

推送没有发生，我得到了这个

The following assertion was thrown while handling a gesture: 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.

Another exception was thrown: Navigator operation requested with a context that does not include a Navigator.

怎么了？

最佳答案

将 Flutter 中的小部件想象成一棵树，其上下文指向使用 build 函数构建的任何节点。在你的情况下，你有

MainScreen    <------ context
  --> MaterialApp
   (--> Navigator built within MaterialApp)
      --> Scaffold
        --> App Bar
          --> ...
        --> Center
          --> FlatButton

因此，当您使用上下文查找导航器时，您使用的是不在导航器下方的 MainScreen 上下文。

您可以创建一个新的 Stateless 或 Stateful Widget 子类来包含您的 Center + FlatButton，因为其中的构建函数将指向该级别，或者您可以使用 Builder并定义 builder 回调(它有一个指向 Builder 的上下文)以返回 Center + FlatButton。

关于dart - flutter 导航器不工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50124355/