flutter - 在Flutter中首次启动时的屏幕选择器

Question

首先让我解释一下。
我的应用程序中有三个屏幕。这些是 MyHome.dart ， OtherHome.dart 和 Selector.dart 。
我想在初次启动时启动选择器屏幕。在选择器屏幕中，有两个用户选项。一个是MyHome，另一个是OtherHome。首次启动后，该应用将始终在首次启动时打开用户最后选择的屏幕。正确的代码是什么？
Main.dart :

import 'selector.dart';
import 'package:flutter/material.dart';

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

Selector.dart :

import 'package:device_monitor/home.dart';
import 'package:flutter/material.dart';
import 'home.dart';
import 'myhome.dart';

class Selector extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          RaisedButton(
            onPressed: () {
              Navigator.push(
                context,
                MaterialPageRoute(builder: (context) => MyHome()),
              );
            },
            child: Text('My Device'),
          ),
          SizedBox(height: 30),
          RaisedButton(
            onPressed: () {
              Navigator.push(
                context,
                MaterialPageRoute(builder: (context) => Home()),
              );
            },
            child: Text('Others Device'),
          ),
        ],
      ),
    );
  }
}

Answer 1

以下代码可以为您提供帮助:

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
void main() {
  runApp(MaterialApp(
    home: Selector(),
  ));
}

您需要获得 共享首选项软件包，这是 link

class Selector extends StatefulWidget {
  @override
  _SelectorState createState() => _SelectorState();
}

class _SelectorState extends State<Selector> {
  
  bool pageReady = false;

  /// This checks the whether page has been selected earlier,
  /// should be placed in an initstate function
  _checkPages() async {
    SharedPreferences local = await SharedPreferences.getInstance();
    if(local.getString('page-selected') != null){
      if(local.getString('page-selected') == "1"){
        //navigate to MyHome

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

      } else {
        //Navigate to Home
        Navigator.push(
          context,
          MaterialPageRoute(builder: (context) => Home()),
        );
      }
    } else {
      setState(() {
        pageReady = true;
      });
    }
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _checkPages();
  }

  savePage(String type) async {
    if(type == "1"){
      SharedPreferences local = await SharedPreferences.getInstance();
      local.setString('page-selected', type);
      Navigator.push(
        context,
        MaterialPageRoute(builder: (context) => MyHome()),
      );
    } else {
      SharedPreferences local = await SharedPreferences.getInstance();
      local.setString('page-selected', type);
      Navigator.push(
        context,
        MaterialPageRoute(builder: ( context ) => Home()),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: pageReady ? Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          RaisedButton(
            onPressed: () {
              savePage("1");
            },
            child: Text('My Device'),
          ),
          SizedBox(height: 30),
          RaisedButton(
            onPressed: ()  {
              savePage("2");
            },
            child: Text('Others Device'),
          ),
        ],
      ) : Center(child: CircularProgressIndicator()),
    );
  }
}

class MyHome extends StatefulWidget {
  @override
  _MyHomeState createState() => _MyHomeState();
}

class _MyHomeState extends State<MyHome> {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}


class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container();
  }

因此，我将 Selector()更改为有状态的小部件，并使用 initState()检查用户先前是否已选择页面，如果是，它将用户转到该页面，否则它将打开选择器页面，并且一旦用户选择了页面，我便保存了 session 中的页面也可以使用 savePage()函数。