Flutter - Always execute a function when the page

问题:

How could I make the name() function run whenever the Page1 page appeared?

In the code below before going to Page2 I execute the dispose() Already inside Page2 if I click the back button or the physical button of Android the function name() is not executed, but if I click the 'go to Page1' button the function name() is executed.

Could you help me to always execute the name() function when Page1 appears?

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {  
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new MyHomePage(),
      routes: <String, WidgetBuilder> {
        '/page2': (BuildContext context) => new Page2(),
      },
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String nameScreen;

  String name() {
    return 'foo1';
  }

  @override
  void initState() {
    super.initState();
    this.nameScreen = name();

  }

  @override
  void dispose() {
    this.nameScreen = '';
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Page 1'),
        backgroundColor: new Color(0xFF26C6DA),
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new RaisedButton(
              child: const Text('go to Page2'),
              onPressed: () async {
                dispose();
                bool isLoggedIn = await Navigator.of(context).pushNamed('/page2');
                if (isLoggedIn) {
                  setState((){
                    this.nameScreen = name();
                  });
                }
              },
            ),            
            new Text(
              '$nameScreen',              
            ),
          ],
        ),
      ),
    );
  }
}

class Page2 extends StatelessWidget{
  @override
  Widget build(BuildContext context) {
    return new Scaffold( 
      appBar: new AppBar(
        title: new Text('Page 2'),
        backgroundColor: new Color(0xFFE57373)
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new RaisedButton(
              child: const Text('go back to Page1'),
              onPressed: () {
                Navigator.pop(context, true);
              }
            ),
          ],
        ),
      ),
    );
  }
}

回答1:

There is no need to call dispose at all when you are willing to pop and change State later, since dispose will remove the current object from the tree, which does not translate to the logic you are trying to develop.

You can indeed override the BackButton and pass the same call of Navigator.pop(context, result) to it. Check the following example I have tweaked your code a little bit to show you the difference between each State of your nameScreen field. I hope this helps you.

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String nameScreen = "";

  String name() {
    return 'foo1';
  }

  @override
  void initState() {
    super.initState();
    this.nameScreen = "From initState";

  }

@override
void dipose(){
    super.dispose();
}

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Page 1'),
        backgroundColor: new Color(0xFF26C6DA),
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new RaisedButton(
              child: const Text('go to Page2'),
              onPressed: () async {
                //dispose(); ///No need for dispose
                String result = await Navigator.of(context).pushNamed('/page2');

                  setState((){
                    this.nameScreen = result;
                  });

              },
            ),
            new Text(
              '$nameScreen',
            ),
          ],
        ),
      ),
    );
  }
}

class Page2 extends StatelessWidget{
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
          leading: new IconButton(icon: new Icon(Icons.arrow_back), onPressed: ()async{
            Navigator.pop(context,"From BackButton");
          }),
          title: new Text('Page 2'),
          backgroundColor: new Color(0xFFE57373)
      ),
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new RaisedButton(
                child: const Text('go back to Page1'),
                onPressed: () {
                  Navigator.pop(context, "From RaisedButton");
                }
            ),
          ],
        ),
      ),
    );
  }