Flutter Webview Back Button Controller - flutter

Question

I have a Flutter project with Bottom Navigation Bar. There are 2 tabs in the Bottom Navigation Bar. One page is webview and the other is flutter page. I add these two pages to my home page with include. I want to manage the navigation in the webview when the back button is pressed while the inside webview is on the page.
Home Page Code:
Future<bool> _onBackPressed() {
return (showDialog(
context: context,
builder: (context) => new AlertDialog(
title: new Text('Sure?'),
content:
new Text('???'),
actions: <Widget>[
TextButton(
onPressed: () => Navigator.of(context).pop(false),
child: new Text('No'),
),
TextButton(
onPressed: () => Navigator.of(context).pop(true),
child: new Text('Yes'),
),
],
),
)) ??
false;
}
#override
Widget build(BuildContext context) {
List<Widget> pageList = [
MainHomePage(
text: widget.text,
),
WatchPage()
];
return WillPopScope(
onWillPop: _onBackPressed,
child: Scaffold(
//backgroundColor: Colors.transparent,
body: Container(
child: pageList[_activePage],
),
bottomNavigationBar: CurvedNavigationBar(
animationCurve: Curves.easeInOut,
animationDuration: Duration(milliseconds: 600),
color: Color(0xff1f5269),
backgroundColor: Colors.transparent,
onTap: (index) {
setState(() {
_activePage = index;
});
},
items: <Widget>[
Icon(
Icons.home,
color: Colors.white,
),
Icon(
Icons.tv,
color: Colors.white,
),
],
),
),
);
}
WebView Page:
WebViewController controller;
final Completer<WebViewController> _controller =
Completer<WebViewController>();
Future<void> _onWillPop(BuildContext context) async {
print("onwillpop");
if (await controller.canGoBack()) {
controller.goBack();
return Future.value(true);
} else {
//exit(0);
return Future.value(false);
}
}
#override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () => _onWillPop(context),
child: Scaffold(
appBar: AppBar(
toolbarHeight: 10,
flexibleSpace: Container(
color: Color(0xff1f5269),
),
),
body: Builder(builder: (BuildContext context) {
return WebView(
initialUrl: widget.text,
javascriptMode: JavascriptMode.unrestricted,
onWebViewCreated: (WebViewController c) {
_controller.future.then((value) => controller = value);
_controller.complete(c);
},
onProgress: (int progress) {
//print("Webview is loading(progress: $progress&)");
},
onPageStarted: (String url) {
if (url == "https://app.testt.com/Login/Cikis") {
Navigator.of(context, rootNavigator: true).push(
MaterialPageRoute(builder: (context) => new LoginPage()));
}
},
onPageFinished: (String url) {
if (url == "https://app.testt.com/Login" ) {
Navigator.of(context, rootNavigator: true).push(
MaterialPageRoute(builder: (context) => new LoginPage()));
}
},
gestureNavigationEnabled: true,
);
}),
),
);
}