Flutter/Dart Static variables lost / keep getting reinitialized

I toyed around for an hour and realise what appears to be the reason. Apparently when I do:

import 'package:flutter_test_app/main.dart';

It is different from

import 'main.dart';

Even if both source files belong to the same package.

So in the end my test code looks like:

main.dart:

import 'package:flutter/material.dart';import 'pageA.dart';import 'pageB.dart';import 'pageH.dart';void main() {  runApp(new MyApp());}class MyApp extends StatelessWidget {  static bool testFlag = false;  // This widget is the root of your application.  @override  Widget build(BuildContext context) {    testFlag = true;    ThemeData mainTheme = new ThemeData(      primarySwatch: Colors.cyan,    );    print("testFlag @ MyApp: " + testFlag.toString());    MaterialApp mainApp = new MaterialApp(      title: 'Instabazaar',      theme: mainTheme,      home: new HomePage(title: 'Instabazaar'),    );    return mainApp;  }}class HomePage extends StatefulWidget {  final String title;  HomePage({Key key, this.title}) : super(key: key);  @override  _HomePageState createState() {    return new _HomePageState();  }}class _HomePageState extends State<HomePage> {  int _currentPageID = 0; // 0=home, 1=pageA, 2=pageB  @override  Widget build(BuildContext context) {    print("testFlag @ HomePage: " + MyApp.testFlag.toString());    AppBar appBar = new AppBar(        title: new Text("TestApp"),        centerTitle: true,    );    BottomNavigationBar bottomNavigationBar = new BottomNavigationBar(        type: BottomNavigationBarType.shifting,        items: <BottomNavigationBarItem>[          new BottomNavigationBarItem(icon: new Icon(Icons.home), title: new Text('Home'), backgroundColor: Theme.of(context).accentColor),          new BottomNavigationBarItem(icon: new Icon(Icons.explore), title: new Text('PageA'), backgroundColor: Colors.purple),          new BottomNavigationBarItem(icon: new Icon(Icons.star), title: new Text('PageB'), backgroundColor: Colors.redAccent),        ],        onTap: (i) => setState( () => _currentPageID = i ),        currentIndex: _currentPageID    );    Scaffold mainScaffold = new Scaffold(      appBar: appBar,      body: _getNewSubPage(),      bottomNavigationBar: bottomNavigationBar,    );    return mainScaffold;  }  //MARK: navigation  Widget _getNewSubPage(){    switch (_currentPageID)    {      case 1:        return new pageA();      case 2:        return new pageB();      default:        return new pageH();    }  }}

pageA.dart / pageB.dart:

import 'package:flutter/material.dart';import 'package:flutter_test_app/main.dart';class pageA extends StatefulWidget{  pageAState createState() => new pageAState();}class pageAState extends State<pageA> {  @override  Widget build(BuildContext context) {    print("testFlag @ pageA: " + MyApp.testFlag.toString());    return new Container();  }}

pageH.dart:

import 'package:flutter/material.dart';import 'main.dart';class pageH extends StatefulWidget{  pageHState createState() => new pageHState();}class pageHState extends State<pageH> {  @override  Widget build(BuildContext context) {    print("testFlag @ pageH: " + MyApp.testFlag.toString());    return new Container();  }}

The only difference is the import statement. However, for pageA/pageB, the print statement would give "false". As for pageH, the print statement would give "true". I have switched around the import statements and it checks out. I am not familiar with how dart actually interprets the code, so I am not sure if it is a dart thing, a setup thing or a flutter thing. I will continue investigating but for now my problem is solved.

Thanks for everyone's help.

It seems that Flutter and Dart have issue to find the same instance for static (global) variable if the import starts with: "package:your_app_package/file.dart".

So let say you want to have static variable (myStaticVariable) in your main.dart file, where you have MyApp class. And let say that you want to get that static variable in some different .dart file in your project, by calling it with MyApp.myStaticVariable.

In that case if you import main.dart with "import package:your_app_package/main.dart" the variable will have "null" value , even if it has been initialised before!

If you import main.dart with just "import main.dart" (if the files are in the same directory) or "import ../main.dart" (if your file is one directory dipper then main.dart), you will get the right value for MyApp.myStaticVariable.

I am not sure why is that, but maybe like @Kevin Moore mentioned, there is an issue and Flutter team needs to resolve it.

class Glob {  //One instance, needs factory   static Glob _instance;  factory Glob() => _instance ??= new Glob._();  Glob._();  //  String account ='johanacct1';  String getServerUrl(){    return 'http://192.168.1.60';  }  String getAccountUrl(){    return getServerUrl()+'/accounts/'+account;  }}

Use it in another file:

`

Glob().getAccountUrl(); //http://192.168.1.60/accounts/johanacct1Glob().account = 'philip.k.dick';Glob().getAccountUrl(); //http://192.168.1.60/accounts/philip.k.dick

`It works with import 'glob.dart'; when both files are in the lib/ directory. (IDK if there are problems in other scenarios.)