How to get state changed value after widget build? - flutter

Question

I have simple application where I work with user location. On first app open I will ask from user to allow location and then save to var. But when I try check inside widget location allow status it is return old value instance of changed value.
Code
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:yandex_mapkit/yandex_mapkit.dart';
import 'package:permission_handler/permission_handler.dart';
class PlacesListScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
return _Map();
}
}
class _Map extends StatefulWidget {
#override
_MapState createState() => _MapState();
}
class _MapState extends State<_Map> {
YandexMapController controller;
PermissionStatus _permissionStatus = PermissionStatus.undetermined;
#override
void initState() {
super.initState();
_requestPermission();
}
Future<void> _requestPermission() async {
Map<Permission, PermissionStatus> permissions =
await [Permission.location].request();
setState(() {
_permissionStatus = permissions[Permission.location];
});
}
void _showMessage(BuildContext context, Text text) {
final ScaffoldState scaffold = Scaffold.of(context);
scaffold.showSnackBar(
SnackBar(
content: text,
action: SnackBarAction(
label: 'OK', onPressed: scaffold.hideCurrentSnackBar),
),
);
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('App Name'),
actions: <Widget>[
IconButton(
icon: Icon(Icons.add),
onPressed: null,
),
],
),
body: Text('App Content'),
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
floatingActionButton: Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
FloatingActionButton(
onPressed: () async {
if (_permissionStatus == PermissionStatus.granted) {
await Future.wait([
controller.moveToUser(),
controller.showUserLayer(
iconName: 'lib/assets/arrow.png',
arrowName: 'lib/assets/user_location1.png',
accuracyCircleFillColor: Colors.green.withOpacity(0.5),
)
]);
} else {
_showMessage(context, const Text('Permission Denied'));
}
},
child: Icon(Icons.place, color: Colors.white),
backgroundColor: Colors.green,
heroTag: 'showUserLocation',
),
],
),
);
}
}
Using FloatingActionButton I tried check Permission status in my code. But my var _permissionStatus doesn't updated when user allowed location. How to fix this problem and get changed value from state?

Answer 1

You can use this package: https://pub.dev/packages/location
and then you can read the permission status:
Location location = new Location();
PermissionStatus _permissionGranted;
_permissionGranted = await location.hasPermission();
if (_permissionGranted == PermissionStatus.denied) {
_permissionGranted = await location.requestPermission();
if (_permissionGranted != PermissionStatus.granted) {
return;
}
}
another way:
location.hasPermision().then(PermissionStatus status){
if (_permissionGranted == PermissionStatus.denied){
location.requestPermission().then((PermissionStatus requestStatus){
// save the value
}
);
}
});

Answer 2

You need to know when user grand the permission then you know it, you must use the wrap your widget with FocusScope like this:
first define this:
final _focusNode = FocusScopeNode();
then wrap it with this:
return FocusScope(
node: _focusNode,
child: WillPopScope(
onWillPop: () async {
_requestPermission();
},.....