从main（）调用await rootBundle.loadString（…）时，Flutter应用程序挂起

Posted 2023-01-08

我发现this answer关于将全局配置存储到globals.dart。

如何从assets/config.json将配置加载到其中？

我已经这样尝试过：

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'dart:convert';
import 'globals.dart' as globals;

void main() async 
  globals.config = jsonDecode(await rootBundle.loadString('assets/config.json'));
  runApp(MyApp());


class MyApp extends StatelessWidget 
  ...

应用程序以白屏开头。什么都没有发生，没有错误。我猜想await rootBundle.loadString(...)导致应用程序挂起。

答案

您可以在下面复制粘贴运行完整代码您需要在WidgetsFlutterBinding.ensureInitialized()中添加main()没有这条线会产生白屏

globals.dart

Map<String, dynamic> config = ;

config.json

    
    "id": "1",
    "name": "abc"

代码段

void main() async
      WidgetsFlutterBinding.ensureInitialized();
      globals.config = jsonDecode(await rootBundle.loadString('assets/config.json'));
      runApp(MyApp());
    

pubspec.yaml

assets:
  - assets/

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'dart:convert';
import 'globals.dart' as globals;

void main() async
  WidgetsFlutterBinding.ensureInitialized();
  globals.config = jsonDecode(await rootBundle.loadString('assets/config.json'));
  runApp(MyApp());


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


class MyHomePage extends StatefulWidget 
  MyHomePage(Key key, this.title) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();


class _MyHomePageState extends State<MyHomePage> 
  int _counter = 0;

  void _incrementCounter() 
    setState(()      
      _counter++;
    );
  

  @override
  Widget build(BuildContext context)     
    return Scaffold(
      appBar: AppBar(        
        title: Text(widget.title),
      ),
      body: Center(        
        child: Column(         
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(globals.config["id"]),
            Text(globals.config["name"]),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), 
    );