catch Android back button event on Flutter

In order to prevent navigating back WillPopScope is the correct way and should be used as follow:

class Page2 extends StatelessWidget {  @override  Widget build(BuildContext context) {    return new WillPopScope(      child: new Scaffold(        appBar: new AppBar(          title: new Text('Page 2'),        ),        body: new Center(          child: new Text('PAGE 2'),        ),      ),      onWillPop: () async {        return false;      },    );  }}Future<T> pushPage<T>(BuildContext context, Widget page) {  return Navigator.of(context)      .push<T>(MaterialPageRoute(builder: (context) => page));}

Can call the page like:

pushPage(context, Page2());

This is should be helpful.

@overrideWidget build(BuildContext context) {  return WillPopScope(    onWillPop: () {      _moveToScreen2(context, );    },    child: Scaffold(      key: _scaffoldKey,      appBar: AppBar(        leading: IconButton(            icon: Icon(Icons.arrow_back),            onPressed: () {              _moveToScreen2(context);            }),        title: Text("Screen 1"),      ),    ),  );}/*** This is probably too thin to be in its own method - consider using* `Navigator.pushReplacementNamed(context, "screen2")` directly*/void _moveToScreen2(BuildContext context) =>    Navigator.pushReplacementNamed(context, "screen2");

This code work for me.

I think there may be two reasons.

1. Child of WillPopScope is Scaffold

2. No return in onWillPop

   return new WillPopScope(  onWillPop: () {    if (!_isOpened) Navigator.pop(context);  },  child: new Scaffold(    key: SharedService.orderScaffoldKey,    appBar: appBar,    body: new Builder(      builder: (BuildContext context) {        return page;      },    ),  ),);