颤动一次介绍屏幕？

Question

我有一个我的应用程序的介绍屏幕,但它显示我每次打开应用程序, 我需要第一次显示, 如何做到这一点？

//ThIS IS THE SCREEN COMES 1ST WHEN OPENING THE APP (SPLASHSCREEN)

class SplashScreen extends StatefulWidget {
@override
_SplashScreenState createState() => _SplashScreenState();
}

class _SplashScreenState extends State<SplashScreen> {
@override
void initState() 
{
super.initState();

//After 2seconds of time the Introscreen will e opened by bellow code
Timer(Duration(seconds: 2), () => MyNavigator.goToIntroscreen(context));
}

//The below code has the text to show for the spalshing screen
@override
Widget build(BuildContext context)
{
return Scaffold
(
body: new Center(child:Text('SPLASH SCREEN'),)
);
}
}

此屏幕始终打开内部屏幕,延迟时间为2秒.但我只是第一次想要如何使用共享偏好？请添加所需的代码请....

Answer 1

如果您希望仅首次显示介绍屏幕,则需要在本地保存此用户已经看过的介绍.

对于这样的事情,您可以使用共享首选项.您可以使用共享首选项的颤振包

编辑:

请参阅以下完整测试代码以了解如何使用它:

import 'dart:async';

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

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

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
    return new MaterialApp(
    color: Colors.blue,
    home: new Splash(),
    );
}
}

class Splash extends StatefulWidget {
@override
SplashState createState() => new SplashState();
}

class SplashState extends State<Splash> {
Future checkFirstSeen() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    bool _seen = (prefs.getBool('seen') ?? false);

    if (_seen) {
    Navigator.of(context).pushReplacement(
        new MaterialPageRoute(builder: (context) => new Home()));
    } else {
    prefs.setBool('seen', true);
    Navigator.of(context).pushReplacement(
        new MaterialPageRoute(builder: (context) => new IntroScreen()));
    }
}

@override
void initState() {
    super.initState();
    new Timer(new Duration(milliseconds: 200), () {
    checkFirstSeen();
    });
}

@override
Widget build(BuildContext context) {
    return new Scaffold(
    body: new Center(
        child: new Text('Loading...'),
    ),
    );
}
}

class Home extends StatelessWidget {
@override
Widget build(BuildContext context) {
    return new Scaffold(
    appBar: new AppBar(
        title: new Text('Hello'),
    ),
    body: new Center(
        child: new Text('This is the second page'),
    ),
    );
}
}

class IntroScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
    return new Scaffold(
    body: new Center(
        child: new Column(
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
            new Text('This is the intro page'),
            new MaterialButton(
            child: new Text('Gogo Home Page'),
            onPressed: () {
                Navigator.of(context).pushReplacement(
                    new MaterialPageRoute(builder: (context) => new Home()));
            },
            )
        ],
        ),
    ),
    );
}
}

Answer 2

我可以不使用 after_layout 包和 Mixins，而是使用了 FutureBuilder。

class SplashState extends State<Splash> {
  Future checkFirstSeen() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    bool _seen = (prefs.getBool('seen') ?? false);

    if (_seen) {
      return HomeScreen.id;
    } else {
        // Set the flag to true at the end of onboarding screen if everything is successfull and so I am commenting it out
      // await prefs.setBool('seen', true);
      return IntroScreen.id;
    }
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
        future: checkFirstSeen(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return Center(
              child: CircularProgressIndicator(),
            );
          } else {
            return MaterialApp(
              initialRoute: snapshot.data,
              routes: {
                IntroScreen.id: (context) => IntroScreen(),
                HomeScreen.id: (context) => HomeScreen(),
              },
            );
          }
        });
  }
}

class HomeScreen extends StatelessWidget {
static String id = 'HomeScreen';
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Hello'),
      ),
      body: new Center(
        child: new Text('This is the second page'),
      ),
    );
  }
}

class IntroScreen extends StatelessWidget {
static String id = 'IntroScreen';
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('IntroScreen'),
      ),
      body: new Center(
        child: new Text('This is the IntroScreen'),
      ),
    );
  }
}