I am having trouble identifying as to why setState() is returning null on my shared preferences getString method.
I am calling an async function outside of the initState and the constantly printing null when i check the return string of getString on page load.
I have checked that setString is saving the correct string to the key.
Here is my code:
void initState() {
super.initState();
retrieve();
}
retrieve() async {
final prefs = await SharedPreferences.getInstance();
setState(() {
name = prefs.getString("displayName");
print(name);
});
}
Here is where I setString(in the register user page):
try {
UserCredential result =
await FirebaseAuth.instance.createUserWithEmailAndPassword(
email: _emailController.text,
password: _passwordController.text,
);
final user = FirebaseAuth.instance.currentUser;
final name = _usernameController.text;
// if (user != null) {
await user?.updateDisplayName(name);
Navigator.pushNamed(context, homeRoute);
print(name);
You should set ,username via shared preference before accessing it.
final prefs = await SharedPreferences.getInstance();
In register page.(where you want to set name via SharedPreference before accessing it)
await prefs.setString('displayName', 'name');
After setting it in registeration you can access like above
name = prefs.getString("displayName");
When SharedPreferences return null value it means you have not set value with your key yet. So firstly set something like this:
final prefs = await SharedPreferences.getInstance().reload();
await prefs.setString('displayName', 'Mark');
then try to call it.
Thanks to all who have spent the time to respond to help. I hope this answer might help some one else down the track.
I found that Shared Preferences was not saving the data - my code was fine after all. I simply just closed the app and restarted the X code build from scratch and it is now working.....
Related
I am coding a to-do list app in flutter but every time I close the app, all my to-do's are gone, and none of them are stored. How do I stop them from disappearing every time I close the app?
Use sqlite or files. Please refer documentation on cookbooks for either approach.
https://docs.flutter.dev/cookbook/persistence
Your other option is to use an external database over the internet
To persist your data (todo list) you can either
store data on the users device
You can do this by using a local databases like sqflite, sqfentity, shared_preferences etc
or store the data on the server
Using this option you can either spin up your own server or use some quick serverless solutions like supabase or cloud firestore from firebase.
I recommend hive it’s very easy to use and it’s lightweigh.
In addition with all the other propositions, you can try Isar, which is a NoSQL local database that can be used for all platforms:
https://isar.dev/tutorials/quickstart.html
https://pub.dev/packages/isar
Apps generally store data in temporary storage which destroyed every time yo close the app. in order to save data permanently, you could use sqflite database or shared_preferences database
if you want use shared_preferences, you can do this:
first make class that call StorageManager:
import 'package:shared_preferences/shared_preferences.dart';
class StorageManager {
static Future<bool> saveData(String key, dynamic value) async {
final prefs = await SharedPreferences.getInstance();
await prefs.reload();
if (value is int) {
prefs.setInt(key, value);
return true;
} else if (value is String) {
prefs.setString(key, value);
return true;
} else if (value is bool) {
prefs.setBool(key, value);
return true;
} else {
return false;
}
}
static Future<dynamic> readData(String key) async {
final prefs = await SharedPreferences.getInstance();
await prefs.reload();
dynamic obj = prefs.get(key);
return obj;
}
static Future<bool> deleteData(String key) async {
final prefs = await SharedPreferences.getInstance();
return prefs.remove(key);
}
static Future<void> reloadSharedPreferences() async {
final prefs = await SharedPreferences.getInstance();
await prefs.reload();
}
}
then use it like this:
when you want save some thing in storage call this:
await StorageManager.saveData('some unique key', your int or string or bool value);
when you want read from storage:
var result = await StorageManager.readData('some unique key');
if (result != null) {
// use your value
} else {
// this means there is no result
}
I'm trying to show a page as an initial login, this is only displayed when my switch value is set to true.
The switch value is stored with shared preferences but when I open the application it is not recovered, only after an application update is it actually recovered. how can i get it to be recovered instantly when i open my application?
below the code:
Future<bool> saveSwitchState(bool value) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setBool("switched", value);
print('Switch Value saved $value');
return prefs.setBool("switched", value);
}
Future<bool> getSwitchState() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
SettingsPage.switched = prefs.getBool("switched")!;
print(SettingsPage.switched);
return SettingsPage.switched;
}
on another page then the value that is actually recovered:
if(AuthPage.authenticated == false && SettingsPage.switched == true ) {
yield ProfileNoAuth();
return; }
you can use dependency injection follow these steps :
get it package
create a Separate dart containing the following code file like this:
GetIt locator = GetIt.instance;
Future<void> setupLocator() async {
SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
locator.registerLazySingleton<SharedPreferences>(() => sharedPreferences);
}
call the setupLocator() method and wait for it in your main function
void main() async {
await setupLocator();
runApp(App());
}
access SharedPreferences Instance from anywhere like this:
locator();
now the SharedPreferences Instance if available anywhere in your project
please note that you dont have to wait for getting the Instance anymore, because you have only one Instance sharable across the application
bool getSwitchState() {
final prefs = locator<SharedPreferences>();
SettingsPage.switched = prefs.getBool("switched")!;
print(SettingsPage.switched);
return SettingsPage.switched;
}
I can't work out how to return a string from a function in Dart (a Flutter app).
I am using SharedPreferences to capture input from the user. I have two functions, one to save preferences:
save(key, value) async {
final prefs = await SharedPreferences.getInstance();
prefs.setString(key, value);
print('saved $value');
}
and one to read preferences:
read(key) async {
final prefs = await SharedPreferences.getInstance();
final value = prefs.getString(key) ?? 0;
print('$value');
}
This is working, but when I try to replace the print line with a return:
read(key) async {
final prefs = await SharedPreferences.getInstance();
final value = prefs.getString(key) ?? 0;
return('$value');
}
to return a string for the value, it throws an error:
type 'Future' is not a subtype of type 'String'
I have tried calling it many MANY different ways, but can't figure out what I assume is an incredibly basic problem. I noticed in some posts that this is a suggested solution, which works to print out the value, but I don't want to print it, i want it as a String variable:
read(mykey).then((value) => '$value');
I need to combine the value with other some other string values and make some minor manipulations (so printing it isn't helpful)
UPDATE
I have defined the function as #Stijn2210 suggested, but am still having problems getting the output i need.
Future<String> read(key) async {
final prefs = await SharedPreferences.getInstance();
final value = await prefs.getString(key) ?? '';
return value;
}
When I call this function from my app (this is a simplified snippet):
void onDragEnd(DraggableDetails details, User user) {
final minimumDrag = 100;
Future<String> myvalue;
if (details.offset.dx > minimumDrag) {
user.isSwipedOff = true;
save(user.imgUrl, 'Dog');
}
myvalue = read(user.imgUrl);
print(myvalue);
It's printing :
Instance of 'Future'
Whereas I want myvalue to be 'Dog'... Appreciate any insights!!
Really appreciate your answer #Stijn2202
Solution was to edit the method definition:
Future<void> onDragEnd(DraggableDetails details, User user) async
and then call the read function from the method with this:
final String myvalue = await read(user.imgUrl);
getString is a Future, which you can handle by using await or as you are doing, using then
However, in my opinion using await is your better option. This would look like this:
Future<String> getMyString() async {
final prefs = await SharedPreferences.getInstance();
final value = await prefs.getString(key) ?? '';
// Don't use 0, since it isnt an int what you want to return
return value;
}
EDIT:
based on your code snippet, this is how you should call your read method:
Future<void> onDragEnd(DraggableDetails details, User user) async {
final minimumDrag = 100;
if (details.offset.dx > minimumDrag) {
user.isSwipedOff = true;
save(user.imgUrl, 'Dog');
}
final String myvalue = await read(user.imgUrl);
print(myvalue);
}
Now I'm not sure if onDragEnd is actually allowed to be Future<void>, but let me know if it isn't
Just await for the value. It will return Dog and not instance of Future.
String someName=await myvalue;
As the value is Future, await keyword will wait until the task finishes and return the value
so newbie question but i think i have done everything in accordance with the documentation and i can't find the bug i have List string with shared preferences and 3 function laod save delete ,load and save work perfect but delete doing nothing without errors :/
List favorites=[];
#override
void initState(){
super.initState();
setState(() {
_loadList();
});}
_loadList() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
favorites = (prefs.getStringList('myFavorites') ?? []);
});
}
_saveList(documentID) async{
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setStringList('myFavorites', ['$documentID']);
_loadList();
}
_deleteList(documentID) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
var list= prefs.getStringList('myFavorites');
list.remove(documentID);
_loadList();}
I couldn't find too many questions about it, I think my own stupidity forgets something. can someone help ?
I made a new list and add all keys to new list. deleted documentId in my new list and put the new list in place of myFavorites. Also works.
Iam using flutter and I am trying to get a value from shared_preferences that I had set before, and display it in a text widget. but i get Instance of Future<String> instead of the value. here is my code:
Future<String> getPhone() async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
final String patientPhone = prefs.getString('patientPhone').toString();
print(patientPhone);
return patientPhone;
}
Future<String> phoneOfPatient = getPhone();
Center(child: Text('${phoneOfPatient}'),))
There is await missing before prefs.getString( and use setState() instead of returning the value. build() can't use await.
String _patientPhone;
Future<void> getPhone() async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
final String patientPhone = await /*added */ prefs.getString('patientPhone');
print(patientPhone);
setState(() => _patientPhone = patientPhone);
}
build() {
...
Center(child: _patientPhone != null ? Text('${_patientPhone}') : Container(),))
}
If you don't have the option to use await or async you can do the following.
getPhone().then((value){
print(value);
});
and then assign a variable to them. From that, you'll have the result from the value.