如何在 Flutter 的小部件树中将新 MaterialPageRoute 作为子项打开

Question

In the example below when I push new MaterialPageRoute it is created on the same level as Home widget in the Flutter widget tree. I would like to have it as a child of widget Home, so Home would be a parent of Child widget.

Here is a full code:

import 'package:flutter/material.dart';

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

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Center(
            child: Text("This is home"),
          ),
          RaisedButton(
            child: Text("Open child view"),
            onPressed: () {
              Navigator.of(context)
                  .push(MaterialPageRoute(builder: (context) => Child()));
            },
          )
        ],
      ),
    );
  }
}

class Child extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Container(
      child: Text("Child view"),
    ));
  }
}

Here is how the widget tree looks like

I want to achieve that because I would like to initialize the ScopedModel in Home widget and have it available in every new MaterialPageRoute I create.

Answer 1

I solved my issue using nested Navigator.

Here is the example:

import 'package:flutter/material.dart';

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

var homeNavigatorKey = GlobalKey<NavigatorState>();

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Navigator(
        key: homeNavigatorKey,
        onGenerateRoute: (settings) {
          /*dirty code for illustration purposes only*/
          if (settings.name == '/child') {
            return MaterialPageRoute(builder: (context) => Child());
          } else {
            return MaterialPageRoute(
                builder: (context) => Column(
                      children: <Widget>[
                        Center(
                          child: Text("This is home"),
                        ),
                        RaisedButton(
                          child: Text("Open child view"),
                          onPressed: () {
                            homeNavigatorKey.currentState.pushNamed('/child');
                          },
                        )
                      ],
                    ));
          }
        },
      ),
    );
  }
}

class Child extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Container(
      child: RaisedButton(
        onPressed: () => Navigator.of(context).pop(),
        child: Text("Back to home"),
      ),
    ));
  }
}

The tree looks like this

and allows for passing data from Home to every child.

Feel free to comment or post answers if you have any simpler solution.

Answer 2

Navigator.of(context).push() will replace your Home screen with a new screen (while keeping the Home screen in memory so you can go back to it). They are on the same level in the widget tree, the only way to nest them is to use nested Navigators I think.

But, given what you want to achieve: why not initialize the ScopedModel one level up and provide at the root of your widget tree? That way you can access your model both in the Home screen as well as the Child screen.

Below is how you could do that, I added a simple ScopedModel and am able to access it's text property inside the Child screen.

import 'package:flutter/material.dart';
import 'package:scoped_model/scoped_model.dart';
import 'package:tryout/model.dart';

void main() {
  runApp(
    ScopedModel<TestModel>(
      model: TestModel(),
      child: MaterialApp(
        home: Home(),
      ),
    )
  );
}

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Center(
            child: Text("This is home"),
          ),
          RaisedButton(
            child: Text("Open child view"),
            onPressed: () {
              Navigator.of(context)
                  .push(MaterialPageRoute(builder: (context) => Child()));
            },
          )
        ],
      ),
    );
  }
}

class Child extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Container(
      child: Text("${ScopedModel.of<TestModel>(context).text}"),
    ));
  }
}

And here's the TestModel class:

import 'package:scoped_model/scoped_model.dart';

class TestModel extends Model {
  String _text = "Test to see if this works!";
  String get text => _text;
}