I have a MainScreen (stateful) with the following method:
#override
void initState() {
super.initState();
WidgetsBinding.instance
.addPostFrameCallback((_) async {
loadFirebaseUser(context);
});
}
My 'loadFirebaseUser' method is in another file called Constants.dart which can be used from any screen.
The function is as follows:
Future<bool> loadFirebaseUser(BuildContext context) async {
Auth _auth = Auth();
FirebaseUser cUser = await _auth.currentUser();
if (cUser.isEmailVerified) {
DocumentSnapshot snapshot = await Firestore.instance
.collection('Profile')
.document(cUser.uid)
.get();
if (snapshot.data != null) {
User user = Provider.of<UserData>(context).getUser();
user = User.fromMap(snapshot);
Provider.of<UserData>(context).setUser(user);
return true;
} else {
return false;
}
}
return false;
}
I am getting the follwing error when this code is executed:
Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.
Needless to say that as result of this the user is not getting loaded. The error points to the following line:
User user = Provider.of<UserData>(context).getUser();
I want the 'loadFirebaseUSer' function to execute automatically and not on any button click, so this is the only place I know to place this code. Is there a way to achieve this differently? Thanks
Did you tried to get context this way?
Future.delayed(Duration.zero, () {
var myState = Provider.of<MyState>(context);
.......
});
Related
I have a code like following in books_overview.dart:
#override
void initState() {
Provider.of<Books>(context).fetchAndSetBooks();
Future.delayed(Duration.zero).then((_) {
Provider.of<Books>(context).fetchAndSetBooks();
});
super.initState();
}
And a code like below within books.dart
Future<void> fetchAndSetBooks([bool filterByUser = false]) async {
final filterString =
filterByUser ? 'orderBy="creatorId"&equalTo="$userId"' : '';
var url = Uri.parse(
'https://flutter-update.firebaseio.com/Books.json?auth=$authToken&$filterString');
try {
final response = await http.get(url);
final extractedData = json.decode(response.body) as Map<String, dynamic>;
if (extractedData == null) {
return;
}
}
And I get the following error:
FlutterError
(dependOnInheritedWidgetOfExactType<_InheritedProviderScope<Books?>>()
or dependOnInheritedElement() was called before
_BooksOverviewScreenState.initState() completed.
At this line of the code inside ``books_overview.dart`:
Provider.of<Books>(context).fetchAndSetBooks();
First of all, I would like to know is this a good way of using provider package(As the origin of the code is from a Flutter tutorial course)?
Secondly I like to know what is the problem and how can I fix it?
PS: I tried to change the first code as following but it didn't help:
#override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) async {
Provider.of<Contests>(context).fetchAndSetContests();
});
}
I am using shared_preferences to store a bool value locally but I think I am doing something wrong.
So first of all, here is my initState:
#override
initState(){
super.initState();
checkIfUserHasData();
getBoolValuesSF();
}
on checkIfUserHasData, Im calling another function at the end (addBoolToSF)
Future<void> checkIfUserHasData ()async {
var collection = FirebaseFirestore.instance.
collection('users').doc(userID).collection('personalInfo');
var querySnapshots = await collection.get();
for (var snapshot in querySnapshots.docs) {
documentID = snapshot.id;
}
await FirebaseFirestore.instance
.collection('users')
.doc(userID)
.collection('personalInfo').doc(documentID)
.get().then((value) {
if (!mounted) return;
setState(() {
gender = value.get('gender');
profileImageUrl = value.get('url');
print(profileImageUrl);
print(gender);
});
});
if (gender != null){
if (!mounted) return;
setState((){
isUserNew = false;
});
if(gender == "Male"){
setState(() => genderIsMale = true);
addBoolToSF();
}else{
setState(() => genderIsMale = false);
addBoolToSF();
}
}else {
return;
}
}
Then addBoolToSF:
addBoolToSF() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setBool('genderType', genderIsMale);
}
Lastely getBoolValuesSF:
getBoolValuesSF() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
bool _genderType = ((prefs.getBool('genderType') ?? true)) ;
genderType = _genderType;
});
}
When the genderType value is obtained I then decide which image to be the background image on the screen:
CachedNetworkImage(
placeholder: (context, url) =>
CircularProgressIndicator(),
imageUrl: genderType ? // : //
With all of that said, here is what is happening when the gender is changed on the firebase firestore:
The first time I navigate or refresh the screen nothing is changed and I get this error:
type 'Null' is not a subtype of type 'bool'
The second time I refresh or navigate to the screen, I do get the correct image on place but I get the same error message again
type 'Null' is not a subtype of type 'bool'
I have tried several ways to solve this issue but i dont seem to get it right.
Edit: I have noticed that when I removed the last part for CachedNetworkImage, I get no error so I think the problem might be on this part
In case like that when you need to wait for a future to build some UI, the go to way is to use a FutureBuilder
You use it like this
FutureBuilder<bool>(
future: getBoolValuesSF,
builder: (BuildContext context, AsyncSnapshot<bool> snapshot) {
// build your UI here based on snapshot value
},
)
checkIfUserHasData() and getBoolValuesSF() both are future method. you can create another async method and put it inside initState.
#override
initState(){
super.initState();
newMthod();
}
newMthod() async{
await checkIfUserHasData();
await getBoolValuesSF();
}
I'm trying to get the return value in my function but the output is 'Instance of Future' instead of the value of school field name in the database
#override
void initState() {
userId = _auth.currentUser!.uid;
publisherSchool =
getName(widget.postInfo['publisher-Id'], 'school').toString();
super.initState();
}
Future getName(String publisherUid, String fieldname) async {
DocumentSnapshot publisherSnapshot = await FirebaseFirestore.instance
.collection('users')
.doc(publisherUid)
.get();
print(publisherSnapshot.get(fieldname));
return publisherSnapshot.get(fieldname);
}
but whenever i'm printing the publisherSnapshop.get(fieldname) i'm getting the correct value from the database
There are 2 ways to do it, you can create a Future method and call it inside the initState like below:
#override
void initState() {
initial();
super.initState();
}
Future<void> initial() async {
userId = _auth.currentUser!.uid;
// Remember using `()` to wrap the `await` to get it result
publisherSchool = (await getName(widget.postInfo['publisher-Id'], 'school')).toString();
}
Or you can use .then to call it directly inside the initState:
#override
void initState() {
userId = _auth.currentUser!.uid;
getName(widget.postInfo['publisher-Id'], 'school').then((value) {
publisherSchool = value.toString();
});
super.initState();
}
When you declare the getName() function, specify the return type as Future<String>, and then when you call getName(), you need to await the result e.g. publisherSchool = await getName(widget.postInfo['publisher-Id'], 'school').toString();
The reason why you are not getting the correct response is because whenever you are working with Futures it takes some time to finish and return the results. Meanwhile it is fetching the result you have to make it await so that the program will continue once that future function is complete since await/then is nowhere to be found in your code hence the issues.
To solve this make this change:
Change
publisherSchool =
getName(widget.postInfo['publisher-Id'], 'school').toString();
To
getName(widget.postInfo['publisher-Id'],
'school').then((value){
publisherSchool=value.toString()});
I am doing an app in flutter and I am working on the authentication part. I want to know how I can keep my user logged in after I reload the app. Now the thing is that my app has 2 kinds of users (Client and Driver). So each has its own space, like sign in and sign up and main (after logging in).
This is the code that I used for logging.
class Initializer extends StatefulWidget {
// Access to this Screen
static String id = 'initializer';
#override
_InitializerState createState() => _InitializerState();
}
class _InitializerState extends State<Initializer> {
// Firebase Stuff
final _auth = FirebaseAuth.instance;
final FirebaseFirestore _firestore = FirebaseFirestore.instance;
User _user;
// To Check if There's a Driver
bool isDriver = true;
void getCurrentUser() async {
try {
final getCurrentUser = _auth.currentUser;
if (getCurrentUser != null) {
getUserKind();
_user = getCurrentUser;
}
} catch (e) {
print(e);
}
}
getUserKind() async {
try {
// To fetch Database for Driver
final QuerySnapshot checkOfDriver =
await _firestore.collection('driver').where('uid', isEqualTo: _user.uid).get().catchError((error) {
print(error);
});
if (checkOfDriver.docs.isEmpty)
setState(() {
isDriver = false;
});
else
setState(() {
isDriver = true;
});
} catch (e) {
print(e);
return null;
}
}
#override
void setState(fn) {
if (mounted) {
super.setState(fn);
}
}
#override
void initState() {
super.initState();
getCurrentUser();
}
#override
Widget build(BuildContext context) {
getCurrentUser();
SizeConfig().init(context);
return _user == null
? WelcomeScreen()
: isDriver
? DriverMain()
: ClientMain();
}
}
It's actually working but not properly, because when I reload the app while I'm logging in as a Client, the app shows me DriverMain at the beginning for one second then it switches to the right side which is ClientMain and that causes me some errors sometimes, and it's not an efficient work anyway.
So, what I should add to the code or ...
Firebase already persists the users credentials, and restores them automatically when the app restarts.
But this is an asynchronous process, as it requires a call to the server. By the time your getCurrentUser = _auth.currentUser code runs, that asynchronous process hasn't finished yet, so you get null.
To properly respond to the auth state being restored (and other changes), you'll want to use an auth state change listener as shown in the documentation on authentication state:
FirebaseAuth.instance
.authStateChanges()
.listen((User? user) {
if (user == null) {
print('User is currently signed out!');
} else {
print('User is signed in!');
}
});
If you want to use this in your UI, you'll typically wrap it in a StreamBuilder instead of calling listen yourself.
I have 3 page I check transitions with bottomNavigationBar first page is Soclose in this page im gettting information from the database and print it on the screen.
I'm getting information from the database smoothly but when i switch screens my console gives warning messages. An error appears in the console, but the application is working properly. When changing screens and returning to the old page(Soclose page), an error page appears and disappears within milliseconds.
I cant find similar questions and i tried to make suggestions in the warnings but either I couldn't do it or the solutions don't work.
Related soclose dart file:
class _Closesevents extends State<Soclose> {
List<Event> eventList;
int eventListLen;
#override
void initState() {
try{
final Future<Database> dbFuture = DbHelper.initializeDatabase();
dbFuture.then((database) {
Future<List<Event>> eventListFuture = DbHelper().getEventList();
eventListFuture.then((eventList) {
setState(() {
this.eventList = eventList;
this.eventListLen = eventList.length;
});
});
});}
catch (e,s)
{
print("[ERROR] $e");
print("[ERROR TREE]\n$s");
}
super.initState();
}
#override
void dispose() {
super.dispose();
}
#override
Widget build(BuildContext context) {
return Container(
child: new ListView.builder(
itemCount: eventListLen,
itemBuilder: (BuildContext context, int index) =>
buildTripCard(context, index)),
);
}
Widget buildTripCard(BuildContext context, int index)
...
Databasehelper file
import ...
class DbHelper {
static DbHelper _databaseHelper; // Singleton DatabaseHelper
static Database _database;
static final String _tablename = EventConstants.TABLE_NAME;
static final String _columnId = EventConstants.COLUMN_ID;
static final String _columnTitle = EventConstants.COLUMN_TITLE;
static final String _columnDate = EventConstants.COLUMN_DATE;
static final String _columnStartTime = EventConstants.COLUMN_STARTTIME;
static final String _columnFinishTime = EventConstants.COLUMUN_FINISHTIME;
static final String _columnDesc = EventConstants.COLUMN_DESCRIPTION;
static final String _columnIsActive = EventConstants.COLUMN_ISACTIVE;
DbHelper._createInstance(); // Named constructor to create instance of DatabaseHelper
factory DbHelper() {
if (_databaseHelper == null) {
_databaseHelper = DbHelper._createInstance(); // This is executed only once, singleton object
}
return _databaseHelper;
}
Future<Database> get database async {
if (_database == null) {
_database = await initializeDatabase();
}
return _database;
}
static Future<Database> initializeDatabase() async {
Directory directory = await getApplicationDocumentsDirectory();
String path = directory.path + 'takvimapp.db';
// Open/create the database at a given path
var notesDatabase = await openDatabase(path, version: 1, onCreate: _createDb);
return notesDatabase;
}
static void _createDb(Database db, int newVersion) async {
await db.execute('CREATE TABLE $_tablename ( $_columnId INTEGER PRIMARY KEY NOT NULL,$_columnTitle TEXT ,$_columnDate TEXT,$_columnStartTime TEXT,$_columnFinishTime TEXT,$_columnDesc TEXT,$_columnIsActive INTEGER);');
}
// Get all events --map
Future<List<Map<String, dynamic>>> getEventMapList() async {
Database db = await this.database;
var result = await db.query(_tablename, orderBy: '$_columnTitle ASC');
return result;
}
// Insert Operation: Insert a Event object to database
Future<int> insertEvent(Event event) async {
Database db = await this.database;
var result = await db.insert(_tablename, event.toMap());
return result;
}
// Update Operation: Update a Event object and save it to database
Future<int> updateEvent(Event event) async {
var db = await this.database;
var result = await db.update(_tablename, event.toMap(), where: '$_columnId = ?', whereArgs: [event.id]);
return result;
}
// Delete Operation: Delete a Event object from database
Future<int> deleteEvent(int id) async {
var db = await this.database;
int result = await db.rawDelete('DELETE FROM $_tablename WHERE $_columnId = $id');
return result;
}
// Get number of Event objects in database
Future<int> getCount() async {
Database db = await this.database;
List<Map<String, dynamic>> x = await db.rawQuery('SELECT COUNT (*) from $_tablename');
int result = Sqflite.firstIntValue(x);
return result;
}
// Convert map to list
Future<List<Event>> getEventList() async {
var eventMapList = await getEventMapList(); // Get 'Map List' from database
int count = eventMapList.length; // Count the number of map entries in db table
List<Event> eventList = List<Event>();
// For loop to create a 'Event List' from a 'Event List'
for (int i = 0; i < count; i++) {
eventList.add(Event.fromMap(eventMapList[i]));
}
return eventList;
}
static Future closeDb() => _database.close();
}
The error warning is constantly written to the console in an infinite loop.
To get rid of the warning, I need to close the app and restart the emulator.
Warning message:
E/flutter (30455): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: setState() >called after dispose(): _CountDownItemState#2bbc3(lifecycle state: defunct, not mounted)
E/flutter (30455): This error happens if you call setState() on a State object for a widget that no >longer appears in the widget tree (e.g., whose parent widget no longer includes the widget in its >build). This error can occur when code calls setState() from a timer or an animation callback.
E/flutter (30455): The preferred solution is to cancel the timer or stop listening to the animation >in the dispose() callback.
Another solution is to check the "mounted" property of this object >before calling setState() to ensure the object is still in the tree.
E/flutter (30455): This error might indicate a memory leak if setState() is being called because >another object is retaining a reference to this State object after it has been removed from the >tree. To avoid memory leaks, consider breaking the reference to this object during dispose().
Solution:
#override
Widget build(BuildContext context) {
return Scaffold(
body: FutureBuilder(
future: _db.getEventList(),
builder: (context, snapshot) {
if (snapshot.data == null) {
return Container(
child: Text("Loading....."),
);
} else {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, int index) {
return ListTile(
title: Text(snapshot.data[index].title),
);
});
}
}),
);
}
The issue is with your initState function override. It's good practice to also call the super of initState, super.initState, before all other logic. Your Futures may be completing too quickly, and calling setState before the state is even initialized. Simply move super.initState(); as the first statement in the override. Ex.
#override
void initState() {
super.initState();//Always call this first
try{
final Future<Database> dbFuture = DbHelper.initializeDatabase();
dbFuture.then((database) {
Future<List<Event>> eventListFuture = DbHelper().getEventList();
eventListFuture.then((eventList) {
setState(() {
this.eventList = eventList;
this.eventListLen = eventList.length;
});
});
});}
catch (e,s)
{
print("[ERROR] $e");
print("[ERROR TREE]\n$s");
}
}
Edit: However, this can still lead to errors as setState could still be called before the widget is mounted. This is why the FutureBuilder widget exists. Wrap the widget that needs this Future data in your build method, pass the Future to the future parameter of the FutureBuilder and access the data with the AsyncSnapshot that the builder provides. See more about FutureBuilder.