flutter 一次介绍屏幕？

Question

我的应用有一个介绍屏幕，但每次打开应用时都会显示，我只需要第一次证明这一点。

怎么做？

//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'),
      ),
    );
  }
}

每次此屏幕打开介绍屏幕时都会延迟 2 秒。但我第一次只想要如何使用 sharedpreference??

请添加所需的代码。

Answer 1

如果您只想首次显示介绍屏幕，您需要在本地保存该用户已经看过介绍的内容。

对于这样的事情，你可以使用 Shared Preference .有一个flutter package对于您可以使用的共享偏好

已编辑:

请引用下面完整的测试代码来了解如何使用它:

import 'dart:async';

import 'package:after_layout/after_layout.dart';
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> with AfterLayoutMixin<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 {
      await prefs.setBool('seen', true);
      Navigator.of(context).pushReplacement(
          new MaterialPageRoute(builder: (context) => new IntroScreen()));
    }
  }

  @override
  void afterFirstLayout(BuildContext context) => 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(
      appBar: new AppBar(
        title: new Text('IntroScreen'),
      ),
      body: new Center(
        child: new Text('This is the IntroScreen'),
      ),
    );
  }
}

感谢 Ben B注意到 initState 中延迟的错误使用。我使用了 delay 因为有时上下文没有立即在 initState 内准备好。

所以现在我用 afterFirstLayout 替换了它，它已经准备好了上下文。您将需要安装包 after_layout .