Navigating through flutter screens automatically - flutter

Question

I'm developing an app that is using location data. So in the landing screen, I will check whether the permission to access location data is granted or not. I do this using the geolocator package. When the user grants permission, I will collect the data like current location and then I want to automatically move into another screen, which is the main screen of the app. Is there any way that I'm able to do that?

Answer 1

I'm making a simple app to demonstrate the permission checking and proper handling of the navigation based on the outcome. You can check the below code and commentation to understand the flow:
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: SomeScreen(),
);
}
}
class SomeScreen extends StatelessWidget {
final _scaffoldKey = GlobalKey<ScaffoldState>();
void _determinePosition(context) async {
bool serviceEnabled;
LocationPermission permission;
serviceEnabled = await Geolocator.isLocationServiceEnabled();
// Checking if the service is enabled
if (!serviceEnabled) {
// If not, display a Snackbar
_scaffoldKey.currentState.showSnackBar(SnackBar(
content: Text('Location services are disabled.'),
duration: Duration(seconds: 2),
));
}
// Checking the permission here
permission = await Geolocator.checkPermission();
if (permission == LocationPermission.denied) {
permission = await Geolocator.requestPermission();
if (permission == LocationPermission.deniedForever) {
_scaffoldKey.currentState.showSnackBar(SnackBar(
content: Text(
'Location permissions are permanently denied, we cannot request permissions.'),
duration: Duration(seconds: 2),
));
}
if (permission == LocationPermission.denied) {
_scaffoldKey.currentState.showSnackBar(SnackBar(
content: Text('Location permissions are denied'),
duration: Duration(seconds: 2),
));
}
}
// Finally if the permission is granted, navigate the user to new screen
Position position = await Geolocator.getCurrentPosition();
Navigator.push(context,
MaterialPageRoute(builder: (context) => Home(position: position)));
}
#override
Widget build(BuildContext context) {
return Scaffold(
key: _scaffoldKey,
body: Container(
alignment: Alignment.center,
color: Colors.blue,
child: FlatButton(
onPressed: () => _determinePosition(context),
child: Text("Check permission"),
color: Colors.red,
),
),
);
}
}
// A simple screen to display the position
class Home extends StatefulWidget {
final Position position;
Home({this.position});
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: Center(
child: Text(
'Location: ${widget.position.altitude} ${widget.position.longitude}'),
),
),
);
}
}

Answer 2

If you want your main screen depend on a value or condition I think you could simply use a Streambuilder at your home, whose streamcontroller receives a boolean, depending on which it'll return one screen or another.
Here for example I used this Streambuilder that listens to a boolean. I will change the value of this boolean to true by pressing a button. In my Streambuilder at my home I have the condition that, if the info received, the snapshot.data is true, then it should not return the MyHomePage but instead TheOtherRoute.
import 'dart:async';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
final StreamController<bool> _streamController =
StreamController<bool>.broadcast();
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: StreamBuilder(
stream: _streamController.stream,
builder: (context, snapshot) {
if(snapshot.data == true){
return TheOtherRoute();
}
return MyHomePage();
},
),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('this is a testo'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
child: FlatButton(
color: Colors.black38,
child: Text('Change boolean'),
onPressed: () {
_streamController.add(true);
},
),
),
],
),
),
);
}
}
class FirstRoute extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('First Route'),
),
body: Center(
child: Text('Your boolean changed. Your home page is now FirstRoute()'),
),
);
}
}
Try it out and let me know.