how to handle notifications flutter - dart

Question

I'm using firebase to send notifications to my app what happens is that I reserved the notifications in the terminal but it's not shown in my application
so how can I handle the notification in a widget so it appears inside the application
I'm trying to set state the text message variable so that its value become the notification body instead of null but its not working
my code is that
[import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/material.dart';
import 'package:idb/pages/aboutus.dart';
import 'package:idb/pages/adminpage.dart';
import 'package:idb/pages/changePassword.dart';
import 'package:idb/pages/homepage.dart';
import 'package:idb/pages/logout.dart';
import 'package:idb/pages/newsPage.dart';
import 'dart:io';
class NotificationsPage extends StatefulWidget {
_NotificationsPageState createState() => _NotificationsPageState();
}
class _NotificationsPageState extends State<NotificationsPage> {
final FirebaseMessaging _messaging = new FirebaseMessaging();
//String testMessage;
Map<String, dynamic> testMessage;
void firebaseCloudMessaging_Listeners() {
if (Platform.isIOS) iOS_Permission();
_messaging.getToken().then((token) {
print('notification token $token');
});
_messaging.configure(
onMessage: (Map<String, dynamic> message) async {
// print('message ${message}');
setState(() {
testMessage = message\['notification'\]\['body'\];
print('testMessage ${testMessage}');
});
},
onResume: (Map<String, dynamic> message) async {
// print('message ${message}');
//print('on resume ${message\['notification'\]\['body'\]}');
setState(() {
String testMessage = message\['notification'\]\['body'\];
print('testMessage onResume ${testMessage}');
});
},
onLaunch: (Map<String, dynamic> message) async {
// print('message ${message}');
// print('on launch $message');
setState(() {
String testMessage = message\['notification'\]\['body'\];
print('testMessage onLaunch ${testMessage}');
});
},
);
}
void iOS_Permission() {
_messaging.requestNotificationPermissions(
IosNotificationSettings(sound: true, badge: true, alert: true));
_messaging.onIosSettingsRegistered
.listen((IosNotificationSettings settings) {
print("Settings registered: $settings");
});
}
int _cIndex = 1;
void _incrementTab(index) {
setState(() {
_cIndex = index;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
drawer: new Drawer(
child: new ListView(children: <Widget>\[
new Container(
child: new DrawerHeader(
child: Image.asset('assets/t.jpg'),
),
),
ListTile(
leading: Icon(Icons.home),
title: Text('Home'),
onTap: () {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (BuildContext context) => AdminPage()),
);
},
),
ListTile(
leading: Icon(Icons.credit_card),
title: Text('My Cards'),
onTap: () {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (BuildContext context) => HomePage()),
);
},
),
ListTile(
leading: Icon(Icons.message),
title: Text('News'),
onTap: () {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (BuildContext context) => NewsPage()),
);
},
),
ListTile(
leading: Icon(Icons.info),
title: Text('About Us'),
onTap: () {
Navigator.pushReplacement(
context,
MaterialPageRoute(builder: (BuildContext context) => AboutUs()),
);
},
),
Divider(),
ListTile(
leading: Icon(Icons.lock_outline),
title: Text('Change Password'),
onTap: () {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (BuildContext context) => ChangePassword()),
);
},
),
Logout(),
\]),
),
appBar: AppBar(
title: Text(
'Notifications',
style: TextStyle(color: Colors.blueGrey),
),
backgroundColor: Colors.grey\[100\],
centerTitle: true,
elevation: 0.0,
),
body: Center(
child: Container(
child: Text(
'$testMessage',
style:
new TextStyle(color: Colors.grey, fontWeight: FontWeight.w400),
),
),
),
bottomNavigationBar: BottomNavigationBar(
fixedColor: Colors.orange,
currentIndex: _cIndex,
//fixedColor: Colors.grey\[100\],
type: BottomNavigationBarType.shifting,
items: \[
BottomNavigationBarItem(
icon: Icon(
Icons.home,
color: Colors.blueGrey,
),
title: Text('Home',
style: TextStyle(
color: Colors.blueGrey,
)),
),
BottomNavigationBarItem(
icon: Icon(
Icons.notifications,
color: Colors.blueGrey,
),
title: Text('Notifications',
style: TextStyle(
color: Colors.blueGrey,
)),
),
BottomNavigationBarItem(
icon: Icon(
Icons.message,
color: Colors.blueGrey,
),
title: Text('News',
style: TextStyle(
color: Colors.blueGrey,
)),
),
\],
onTap: (index) {
if (index == 0) {
Navigator.pushReplacement(
context,
MaterialPageRoute(builder: (BuildContext context) => AdminPage()),
);
}
if (index == 1) {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (BuildContext context) => NotificationsPage()),
);
}
if (index == 2) {
Navigator.pushReplacement(
context,
MaterialPageRoute(builder: (BuildContext context) => NewsPage()),
);
}
_incrementTab(index);
// _incrementTab(index);
},
),
);
}
#override
void initState() {
super.initState();
firebaseCloudMessaging_Listeners();
}
}
]1]1