在main.dart中使用FutureBuilder [英] Using FutureBuilder in main.dart

问题描述

下面的代码始终在显示MyHomePage之后总是显示OnboardingScreen一点时间(可能是几毫秒).我相信你们都知道我要做什么.我正在使用FutureBuilder检查getString方法是否有数据.我怎么了或其他任何最佳方式吗?

Below code always show OnboardingScreen a little time (maybe miliseconds), after that display MyHomePage. I am sure that you all understand what i try to do. I am using FutureBuilder to check getString method has data. Whats my fault ? Or any other best way for this ?

saveString() async {
  final prefs = await SharedPreferences.getInstance();
  prefs.setString('firstOpen', '1');
}

getString()方法始终返回字符串.

getString() method always return string.

getString() async {
  final prefs = await SharedPreferences.getInstance();
  String txt = prefs.getString('firstOpen');
  return txt;
}

main.dart

main.dart

home: new FutureBuilder(
            future: getString(),
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                return MyHomePage();
              } else {
                return OnboardingScreen();
              }
            })

推荐答案

通常，我使用的是另一条路由，而不是FutureBuilder.因为futurebuilder每次热重装都会重置futureBuilder.

Usually I'm using another route, rather than FutureBuilder. Because futurebuilder every hot reload will reset the futureBuilder.

在加载数据之前总是会有一些延迟，因此您需要在加载数据之前先显示一些内容.

There always will be some delay before the data loads, so you need to show something before the data will load.

Snapshot.hasData仅显示已解决的将来的返回数据.

Snapshot.hasData is showing only the return data of the resolved future.

import 'dart:async';

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: SplashScreen(),
    );
  }
}

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

const isOnboardingFinished = 'isOnboardingFinished';

class _SplashScreenState extends State<SplashScreen> {
  Timer timer;
  bool isLoading = true;

  @override
  void initState() {
    _checkIfFirstOpen();
    super.initState();
  }

  Future<void> _checkIfFirstOpen() async {
    final prefs = await SharedPreferences.getInstance();
    var hasOpened = prefs.getBool(isOnboardingFinished) ?? false;

    if (hasOpened) {
      _changePage();
    } else {
      setState(() {
        isLoading = false;
      });
    }
  }

  _changePage() {
    Navigator.of(context).pushReplacement(
      // this is route builder without any animation
      PageRouteBuilder(
        pageBuilder: (context, animation1, animation2) => HomePage(),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return isLoading ? Container() : OnBoarding();
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(child: Text('homePage'));
  }
}

class OnBoarding extends StatelessWidget {
  Future<void> handleClose(BuildContext context) async {
    final prefs = await SharedPreferences.getInstance();
    prefs.setBool(isOnboardingFinished, true);
    Navigator.of(context).pushReplacement(
      MaterialPageRoute(
        builder: (_) => HomePage(),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Center(
        child: RaisedButton(
          onPressed: () => handleClose(context),
          child: Text('finish on bording and never show again'),
        ),
      ),
    );
  }
}

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