How to use SharedPreference Globally? - flutter

Question

I pass the value of both userProfileID And ,userstype to Profilepage() as shown below but when i go to profile page and I try to print the value of both this variable I will get Null value, I think they Actually not passed from this _HomePageState, anyone help?
Here is Where I pass the Value of both
userProfileID as a UserID and userstype as UserTypes inside initState() below,
and both UserID and UserTypes are Obtained from SharedPrefrence
(I call GetData to obtain the value of UserID and UserTypes from SharedPreference )
class _HomePageState extends State<HomePage> {
String UserID;
String UserTypes;
List<Widget>_children;
bool isSignedIn= false;
int _CurrentIndex=0;
void initState(){
super.initState();
GetData();
_children=[
TimeLinePage(UsersIdTimeline:UserID,UsersTypeTimeline:UserTypes),
SearchPage(searchUserSID: UserID,searchUsertype:UserTypes), //search(),
UploadPage(uploadUserSID:UserID,uploadUsertype: UserTypes),
NotificationsPage(NotifyUserSID: UserID,NotifyUsertype:UserTypes),
ProfilePage(userProfileID:UserID,userstype:UserTypes),
];
if(FirebaseAuth.instance.currentUser!=null){
setState(() {
isSignedIn= true;
});
}else{
setState(() {
isSignedIn= false;
});
}
}
#override
Widget build(BuildContext context) {
if(isSignedIn){
return buildHomeScreen();
} else{
return buildSignedInScreen();
}
}
void GetData()async {
SharedPreferences preferences= await SharedPreferences.getInstance();
setState(() {
UserID=preferences.get('UserId');
UserTypes=preferences.get('UserType');
});
}
}
here is buildHomeScreen
class _HomePageState extends State<HomePage> {
// ignore: non_constant_identifier_names
String UserID;
String UserTypes;
List<Widget>_children;
List<Widget>_agentchildren;
bool isSignedIn= false;
// ignore: non_constant_identifier_names
int _CurrentIndex=0;
int _agentCurrentIndex=0;
void initState(){
super.initState();
GetData();
_children=[
TimeLinePage(UsersIdTimeline:UserID,UsersTypeTimeline:UserTypes),
SearchPage(searchUserSID: UserID,searchUsertype:UserTypes),
UploadPage(uploadUserSID:UserID,uploadUsertype:UserTypes),
NotificationsPage(NotifyUserSID: UserID,NotifyUsertype:UserTypes),
ProfilePage(userProfileID:UserID,userstype:UserTypes),
];
if(FirebaseAuth.instance.currentUser!=null){
setState(() {
isSignedIn= true;
});
}else{
setState(() {
isSignedIn= false;
});
}
}
#override
Widget build(BuildContext context) {
if(isSignedIn){
if(UserTypes=='agent'){
return buildagentScreen();
} else if(UserTypes== 'Signupuser'||
UserTypes== 'owner'||
UserTypes== 'seller'
){
return buildHomeScreen();
}else{
return buildSignedInScreen();
}
}
}
Here is My ProfilePage(), if I try to get the value of both
( String userstype; String userProfileID;) in this page
i get Null value but I alredy pass the value of them from the above _HomePageState()
class ProfilePage extends StatefulWidget {
String userstype;
String userProfileID;
ProfilePage({this.userProfileID, this.userstype});
#override
_ProfilePageState createState() => _ProfilePageState();
}
class _ProfilePageState extends State<ProfilePage> {
final String CurrentOnlineUserID=curentuser?.uid;
bool loading =false;
int countPost=0;
String postOrientation="grid";
List<Post> PostList=[];
void initState(){
getAllProfilePost();
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.black,
appBar:header(context,strTitle:"profile"),
body:ListView(
children:<Widget>[
TopView(),
]
),
);
}

Answer 1

Use shared preferences globally for your application.
import 'dart:async' show Future;
import 'package:shared_preferences/shared_preferences.dart';
class PreferenceUtils {
static Future<SharedPreferences> get _instance async => _prefsInstance ??= await SharedPreferences.getInstance();
static SharedPreferences _prefsInstance;
// call this method from iniState() function of mainApp().
static Future<SharedPreferences> init() async {
_prefsInstance = await _instance;
return _prefsInstance;
}
static String getString(String key, [String defValue]) {
return _prefsInstance.getString(key) ?? defValue ?? "";
}
static Future<bool> setString(String key, String value) async {
var prefs = await _instance;
return prefs?.setString(key, value) ?? Future.value(false);
}
}
Please follow this link
https://stackoverflow.com/a/61046061/8218866

Answer 2

When the _HomePageState is created, the initState is called, and so this line:
_children=[
[...],
ProfilePage(userProfileID:UserID,userstype:UserTypes),
];
This line is creating the object of a ProfilePage with the desired UserID's and UserTypes. This ProfilePage object will be put inside the _children list.
When you do this:
setState(() {
UserID=preferences.get('UserId');
UserTypes=preferences.get('UserType');
});
You are 1) calling the build method again, and 2) updating the value of UserID and UserTypes. You did not change the value of any itens inside the _childrens list. Or the list itself. Hence the misbehavior you noticed.
There are many ways to solve this, but the essence would be to move this list declaration inside the build method. An example:
#override
Widget build(BuildContext context) {
_children = [.....]
if(isSignedIn){
[...]
Doing this way would not be a pretty way to do it, because you are creating lots of new (and useless) objets every time the build method is called. Maybe in a small application this wouldn't be a problem, and for didactic reasons I chose to show this way in this answer.
The more correct way would be to :
Switch and instantiate inside buildHomeScreen the body object:
Scaffold buildHomeScreen(){
Widget body;
switch (_currentIndex) {
case 0:
body =
TimeLinePage(UsersIdTimeline:UserID,UsersTypeTimeline:UserTypes);
break;
case 1:
body = ...;
break;
}
return Scaffold(
...
body: body,
...
)
}
Which should give you the same result.