Q:

Flutter : PageView keep Stay in previous Screen

I use PageView in my screen to Navigate to another screen. I have 3 screen Home,History and History Detail.
 Everything is fine i can move to history screen. Until i redirect to History Detail from History Screen and i back with Navigator.of(context).pop , I redirect to Home Screen. I want after Back from History Detail i keep stay in History Screen.
 I already initialize initialPage is 0 , and change the initialPage with onPageChanged but nothing happens, i still redirect to Home Screen.
 How can i do for my case?  
It's My Source Code.
  PageController _pageController;
  int currentPage = 0;
  @override
  void initState() {
    _pageController = PageController(initialPage: currentPage);
    super.initState();
  }

 Widget build(BuildContext context) {
    final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
    double mqHeight = MediaQuery.of(context).size.height;
    return Scaffold(
      key: _scaffoldKey,
      body: FutureBuilder(
        future: Hive.openBox("debt_box"),
        builder: (ctx, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            if (snapshot.hasError)
              return Text(snapshot.error.toString());
            else
              return Scaffold(
                body: PageView(
                  scrollDirection: Axis.vertical,
                  onPageChanged: (index) {
                    currentPage = index;
                    print(currentPage);
                  },
                  physics: NeverScrollableScrollPhysics(),
                  controller: _pageController,
                  children: <Widget>[
                    CustomScrollView(
                      slivers: <Widget>[
                        SliverAppBarHome(),
                        SliverListHome(_scaffoldKey),
                      ],
                    ),
                    HistoryDebt(),
                  ],
                ),
              );
          } else {
            return Center(child: CircularProgressIndicator());
          }
        },
      ),
      bottomNavigationBar: BottomAppBar(
        shape: CircularNotchedRectangle(),
        child: Container(
          height: mqHeight * 0.08,
          child: Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: <Widget>[
              IconButton(
                icon: Icon(Icons.home),
                onPressed: () =>
                    functionHelper.previousButtonPageView(_pageController),
              ),
              IconButton(
                icon: Icon(Icons.insert_chart),
                onPressed: () =>
                    functionHelper.nextButtonPageView(_pageController),
              ),
            ],
          ),
        ),
      ),
  }

A:

I found the issue. 
When you press back button it re-builds your main widget. In the build method you have FutureBuilder which also gets rebuild. 
So it will show you CircularProgressIndicator. Since Hive.openBox("debt_box") gives the result instantaneously, you are not able to see it.
While showing CircularProgressIndicator your PageView got deactivated (removed from widget tree). So _pageController loses its client.
After the CircularProgressIndicator, a new PageView gets created. 
That is why it showed Home page  
Solution:
As per the document we should not directly assign future: Hive.openBox("debt_box") during the build. Instead create a Future variable and initialize it in the initState, then pass that variable to future property of FutureBuilder
PageController _pageController;
int currentPage = 0;
Future _openBox;

@override
void initState() {
  _pageController = PageController(initialPage: currentPage);
  _openBox = Hive.openBox("debt_box");  //initialize here
  super.initState();
}

Widget build(BuildContext context) {
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
  double mqHeight = MediaQuery.of(context).size.height;
  return Scaffold(
    key: _scaffoldKey,
    body: FutureBuilder(
      future: _openBox, //pass the future variable here
      builder: (ctx, snapshot) {
      ...

