I'm working on a finance app and I'd like a custom textentry field and keyboard for currency entry with an inbuilt calculator.
I've tried using a BottomSheet, both persistent and modal. The modal behaviour is ideal, but it always shows a barrier. The persistent one is what I have now, using a focus node to show and hide it, but it's throwing strange errors:
I/flutter (30319): The following NoSuchMethodError was thrown while dispatching notifications for FocusNode:
I/flutter (30319): The method 'removeLocalHistoryEntry' was called on null.
I/flutter (30319): Receiver: null
I/flutter (30319): Tried calling: removeLocalHistoryEntry(Instance of 'LocalHistoryEntry')
I/flutter (30319):
I/flutter (30319): When the exception was thrown, this was the stack:
I/flutter (30319): #0 Object.noSuchMethod (dart:core/runtime/libobject_patch.dart:46:5)
I/flutter (30319): #1 LocalHistoryEntry.remove (package:flutter/src/widgets/routes.dart:296:12)
I/flutter (30319): #2 _NumpadFieldState.initState.<anonymous closure> (file:///D:/code/financepie/lib/widgets/numpad/numpadfield.dart:30:32)
...
In any case, the bottom sheet behaviour (dragging down) isn't really ideal to copy the android/ios soft keyboard. Any better solutions? Current code below:
import 'package:flutter/material.dart';
import 'numpad.dart';
class NumpadField extends StatefulWidget {
#override
_NumpadFieldState createState() {
return new _NumpadFieldState();
}
}
class _NumpadFieldState extends State<NumpadField> {
ValueNotifier<List<String>> state;
FocusNode focusNode;
PersistentBottomSheetController bottomSheetController;
#override initState() {
super.initState();
state = ValueNotifier<List<String>>([]);
state.addListener(() => setState((){}));
focusNode = FocusNode();
focusNode.addListener(() {
print(focusNode);
if (focusNode.hasFocus) {
bottomSheetController = showBottomSheet(
context: context,
builder: (context) => Numpad(state: state),
);
} else {
bottomSheetController?.close(); ///this line causing the error
}
});
}
#override dispose() {
state.dispose();
focusNode.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return GestureDetector(
onTap: () {
FocusScope.of(context).requestFocus(focusNode);
},
child: Container(
child: Text(state.value.fold<String>("", (str, e) => "$str $e")),
constraints: BoxConstraints.expand(height: 24.0),
decoration: BoxDecoration(
border: BorderDirectional(bottom: BorderSide())
),
),
);
}
}
bottomSheetController?.close(); is nullable. Since the line causes the error, you can add a null-check to prevent this issue.
else {
if(bottomSheetController != null)
bottomSheetController!.close();
}
Related
I'M currently working on a to-do app following a tutorial
this is the checkbox part
I'm trying to lift it's state up the tree, but when I do so the stateless widget just keeps rebuilding non stop ,
I tried adding key , adding const converting it to stateful but nothing seems to work
it also doesn't provide me with any kind of error or exceptions messages
note : when I set the onChecked to null the statelessWidget runs twice when it should only build once..
below is the code:
import 'package:flutter/material.dart';
class TaskTile extends StatefulWidget {
#override
_TaskTileState createState() => _TaskTileState();
}
class _TaskTileState extends State {
bool isChecked = false;
#override
Widget build(BuildContext context) {
return ListTile(
title: Text(
"Complete Todoey",
style: TextStyle(
decoration: isChecked == true
? TextDecoration.lineThrough
: TextDecoration.none),
),
trailing: TaskCheckBox(
checkBoxState: isChecked,
toggleCheckBoxState:
(bool checkBoxState) {
Future.delayed(Duration.zero,
() async {
setState(() {
print(
"===================$isChecked==============$checkBoxState======================");
isChecked = checkBoxState;
});
});
}),
);
}
}
class TaskCheckBox extends StatelessWidget {
const TaskCheckBox(
{Key? key,
required this.checkBoxState,
required this.toggleCheckBoxState})
: super(key: key);
final bool checkBoxState;
final Function toggleCheckBoxState;
#override
Widget build(BuildContext context) {
print(
"=====================================$checkBoxState+++++++++++++++++++++++++++++++++++++++++");
return Checkbox(
value: checkBoxState,
onChanged:
null, // toggleCheckBoxState(checkBoxState),
);
}
}
a snip from the console output :
Performing hot restart...
Syncing files to device Android SDK built for x86...
I/flutter ( 3401): ===================false==============false======================
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
I/flutter ( 3401): ===================false==============false======================
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
I/flutter ( 3401): ===================false==============false======================
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
I/flutter ( 3401): ===================false==============false======================
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
I/flutter ( 3401): ===================false==============false======================
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
a snip from the output when onChanged is set to null :
Restarted application in 2,694ms.
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
I/flutter ( 3401): =====================================false+++++++++++++++++++++++++++++++++++++++++
The purpose of setState is to tell the framework that a variable in the state has changed and the widget needs to be rebuilt to reflect that change. So calling setState calls the build function again, which in your case recalls your Future, which calls setState again, which triggers build and so on.
To fix this you could get rid of async function with Future.delayed since it's not needed there at all as well as putting print outside your setstate function.
I am trying to implement a simple login/signup screen on flutter, connected to firebase.
The flow is supposed to be as follows:
Main => Wrapper
Wrappper => if user==NULL, then Authenticate, else Home
Authenticate => Login or Signup
The issue is occuring in the Wrapper file. When the code is run, initially the user will be NULL and has to go to the Login screen. However, my code goes directly to the Home screen.
The codes for each file are as follows:
main.dart
void main() async {
await Firebase.initializeApp();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return StreamProvider<MyUser>.value(
value: AuthService().user,
initialData: null,
child: MaterialApp(
home: Wrapper(),
debugShowCheckedModeBanner: false,
)
);
}
}
wrapper.dart
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
final user = Provider.of<MyUser>(context);
if (user == null) {
return Authenticate();
} else {
//return PatientHome();
}
}
}
authenticate.dart
class Authenticate extends StatefulWidget {
#override
_AuthenticateState createState() => _AuthenticateState();
}
class _AuthenticateState extends State<Authenticate> {
bool showSignIn = true;
void toggleView() {
setState(() => showSignIn = !showSignIn);
}
#override
Widget build(BuildContext context) {
if (showSignIn) {
return Login(toggleView: toggleView);
} else {
return Register(toggleView: toggleView);
}
}
}
auth.dart
class AuthService {
final FirebaseAuth _auth = FirebaseAuth.instance;
// create user obj based on firebase user
MyUser _userFromFirebaseUser(User user) {
return user != null ? MyUser(uid: user.uid) : null;
}
// auth change user stream
Stream<MyUser> get user {
return _auth.authStateChanges()
//.map((FirebaseUser user) => _userFromFirebaseUser(user));
.map(_userFromFirebaseUser);
}
// sign in with email and password
Future signInWithEmailAndPassword(String email, String password) async {
try {
UserCredential result = await _auth.signInWithEmailAndPassword(email: email, password: password);
User user = result.user;
return _userFromFirebaseUser(user);
} catch (error) {
print(error.toString());
return null;
}
}
// register with email and password
Future registerWithEmailAndPassword(String email, String password) async {
try {
UserCredential result = await _auth.createUserWithEmailAndPassword(email: email, password: password);
User user = result.user;
return _userFromFirebaseUser(user);
} catch (error) {
print(error.toString()+"oollala");
return null;
}
}
// sign out
Future signOut() async {
try {
return await _auth.signOut();
} catch (error) {
print(error.toString());
return null;
}
}
}
register.dart
class Register extends StatefulWidget {
final Function toggleView;
Register({this.toggleView});
#override
RegisterPatient createState() => RegisterPatient();
}
class RegisterPatient extends State<Register> {
final AuthService _auth = AuthService();
final _formKey = GlobalKey<FormState>();
bool loading = false;
String email = '';
String password = '';
String error = '';
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
appBar: AppBar(
backgroundColor: Colors.deepPurple,
elevation: 0.0,
title: Text('Register'),
actions: <Widget>[
TextButton.icon(
onPressed: () => widget.toggleView(),
icon: Icon(Icons.person),
label: Text('Register as Patient'))
],
),
body: Container(
padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 50.0),
child: Form(
key: _formKey,
child: Column(
children: <Widget>[
SizedBox(height: 20.0),
TextFormField(
validator: (val) => val.isEmpty ? 'Enter email' : null,
onChanged: (val) {
setState(() => email = val);
},
),
SizedBox(height: 20.0),
TextFormField(
obscureText: true,
validator: (val) => val.length < 6 ? 'Enter a password 6+ chars long' : null,
onChanged: (val) {
setState(() => password = val);
},
),
SizedBox(height: 20.0),
RaisedButton(
color: Colors.deepPurple,
child: Text(
'Register',
style: TextStyle(color: Colors.white),
),
onPressed: () async {
if(_formKey.currentState.validate()){
setState(() => loading = true);
dynamic result = await _auth.registerWithEmailAndPassword(email, password);
if(result == null) {
setState(() {
error = 'Email/password incorrect';
loading = false;
});
} else {
Navigator.of(context).pop();
loading = false;
}
}
}
),
SizedBox(height: 12.0),
Text(
error,
style: TextStyle(color: Colors.red, fontSize: 14.0),
)
],
),
),
),
);
}
}
login.dart
similar to register.dart
The issue is that whenever I run this code, it always takes me to HomePage, even though it is supposed to go through the Authenticate file as user is supposed to be NULL.
EDIT 1:
I thought it was directing to Homepage rather than to Authenticate, however my screen is simply white. It does not do anything other than that.
Any idea what could be the issue?
EDIT 2:
The code runs like so, shows a white screen, and never terminated unless I forcibly do so. I changed from emulator to my phone, but it still the same. Any idea what could be the issue? I'm fairly new to flutter so I don't understand the error...
Launching lib\main.dart on sdk gphone x86 arm in debug mode...
Running Gradle task 'assembleDebug'...
√ Built build\app\outputs\flutter-apk\app-debug.apk.
Debug service listening on ws://127.0.0.1:64181/vsky5JbFCKM=/ws
Syncing files to device sdk gphone x86 arm...
E/flutter ( 8057): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: Null check operator used on a null value
E/flutter ( 8057): #0 MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:142:86)
E/flutter ( 8057): #1 MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:148:36)
E/flutter ( 8057): #2 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:331:12)
E/flutter ( 8057): #3 MethodChannel.invokeListMethod (package:flutter/src/services/platform_channel.dart:344:41)
E/flutter ( 8057): #4 MethodChannelFirebase._initializeCore (package:firebase_core_platform_interface/src/method_channel/method_channel_firebase.dart:30:37)
E/flutter ( 8057): #5 MethodChannelFirebase.initializeApp (package:firebase_core_platform_interface/src/method_channel/method_channel_firebase.dart:77:13)
E/flutter ( 8057): #6 Firebase.initializeApp (package:firebase_core/src/firebase.dart:41:47)
E/flutter ( 8057): #7 main (package:hospicare_mobile/main.dart:14:18)
E/flutter ( 8057): #8 _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:142:25)
E/flutter ( 8057): #9 _rootRun (dart:async/zone.dart:1354:13)
E/flutter ( 8057): #10 _CustomZone.run (dart:async/zone.dart:1258:19)
E/flutter ( 8057): #11 _runZoned (dart:async/zone.dart:1789:10)
E/flutter ( 8057): #12 runZonedGuarded (dart:async/zone.dart:1777:12)
E/flutter ( 8057): #13 _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:138:5)
E/flutter ( 8057): #14 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:283:19)
E/flutter ( 8057): #15 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)
E/flutter ( 8057):
I think using shared preferences might help for saving some data inside the app even though the app is closed or restarted by the user .Even you can retrieve it again and if it has something in it you can navigate to homepage , if it is null you can navigate to authenticate page.
Visit :
https://pub.dev/packages/shared_preferences
Follow the steps to use it:
Add the following inside your authenticate page or signin page
SharedPreferences
data=awaitSharedPreferences.getInstance();
data.setString('your_key',your_data);
Add the following inside the main function before runapp function and make the main function as async
SharedPreferences data = await
SharedPreferences.getInstance();
var your_variable = data.getString('your_key');
i cant get subcollection that i created before. i am able to create subcollection named "sinav_gorselleri" after i pressed this RaisedButton and going to SinavOlusturPage with this code:
RaisedButton(
color: Colors.blue,
child: Text("Sınav oluştur"),
onPressed: () async{
final newDoc = await FirebaseFirestore.instance.collection("ders_sinavlari_olusturulanlar")
.add({"baslik": "4oluşturulanSınav2", "gorsel": "gorsel", "konu": "", "ogretmen": "ömer kalfa",
"sira": 3, "tarih": ""});
final idnewDoc = newDoc.id;
debugPrint(idnewDoc);
final newDoc_newCol = await newDoc.collection("sinav_gorselleri")
.add({"gorsel": "https://firebasestorage.googleapis.com/v0/b/sbycpaldemo.appspot.com/o/ders_notlari_gorseller%2Fyeni?alt=media&token=4af59ada-4a8b-45cc-86ef-2f691a5baf62"});
final idnewCol = await newDoc_newCol.id;
debugPrint(idnewCol);
Navigator.of(context,rootNavigator: true).pop('dialog');
Navigator.push(context, MaterialPageRoute(builder: (context)=> SinavOlusturPage(idnewDoc: idnewDoc,)));
}),
and in SinavOlusturPage i am expecting to get first doc in subcollection named "sinav_gorselleri" but cant get it with this code:
import 'dart:io';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
class SinavOlusturPage extends StatefulWidget{
final idnewDoc;
const SinavOlusturPage({Key key, this.idnewDoc}) : super(key: key);
#override
State<StatefulWidget> createState() {
// TODO: implement createState
return SinavOlusturPageState(this.idnewDoc);
}
}
class SinavOlusturPageState extends State {
final idnewDoc;
SinavOlusturPageState(this.idnewDoc);
File _imageSelected;
final _formKey = GlobalKey<FormState>();
final _scaffoldKey = GlobalKey<ScaffoldState>();
#override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(key: _scaffoldKey,
appBar: AppBar(
title: Text("SINAV OLUŞTURMA SAYFASI"),
),
body: ListView(
children: [
Center(
child: Text("..."),
StreamBuilder(
stream: FirebaseFirestore.instance.collection("ders_sinavlari_olusturulanlar/$idnewDoc/sinav_gorselleri").snapshots(),
builder: (context, snapshot){
final querySnapshot = snapshot.data();
return GridView.builder(
itemCount: 3,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
mainAxisSpacing: 10, crossAxisCount: 2,),
itemBuilder: (context, index){
final mapOlusturulan = querySnapshot.docs[index].data();
final idOlusturulan = querySnapshot.docs[index].id;
return GridTile(
child: Center(
child: Image.network(mapOlusturulan["gorsel"])),
);
});
})
],
),
);
}
}
i did tried
FirebaseFirestore.instance.collection("ders_sinavlari_olusturulanlar").doc(idnewDoc) .collection("sinav_gorselleri").snapshots(), also but cant do it. here is my error that i get all the time:
Performing hot reload...
Syncing files to device SNE LX1...
════════ Exception caught by image resource service ════════════════════════════════════════════════
The following ArgumentError was thrown resolving an image codec:
Invalid argument(s): No host specified in URI file:///gorsel
When the exception was thrown, this was the stack:
#0 _HttpClient._openUrl (dart:_http/http_impl.dart:2407:9)
#1 _HttpClient.getUrl (dart:_http/http_impl.dart:2328:48)
#2 NetworkImage._loadAsync (package:flutter/src/painting/_network_image_io.dart:89:59)
#3 NetworkImage.load (package:flutter/src/painting/_network_image_io.dart:50:14)
#4 ImageProvider.resolveStreamForKey.<anonymous closure> (package:flutter/src/painting/image_provider.dart:504:13)
...
Image provider: NetworkImage("gorsel", scale: 1.0)
Image key: NetworkImage("gorsel", scale: 1.0)
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The method 'call' was called on null.
Receiver: null
Tried calling: call()
The relevant error-causing widget was:
StreamBuilder<QuerySnapshot> file:///C:/ornekler/sby_cpal_demo/lib/Dersler/SinavOlusturPage.dart:39:9
════════════════════════════════════════════════════════════════════════════════════════════════════
Reloaded 22 of 694 libraries in 3.748ms.
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building StreamBuilder<QuerySnapshot>(dirty, state: _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot<QuerySnapshot>>#41144):
Class 'QuerySnapshot' has no instance method 'call'.
Receiver: Instance of 'QuerySnapshot'
Tried calling: call()
The relevant error-causing widget was:
StreamBuilder<QuerySnapshot> file:///C:/ornekler/sby_cpal_demo/lib/Dersler/SinavOlusturPage.dart:39:9
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1 SinavOlusturPageState.build.<anonymous closure> (package:sby_cpal_demo/Dersler/SinavOlusturPage.dart:42:50)
#2 StreamBuilder.build (package:flutter/src/widgets/async.dart:525:81)
#3 _StreamBuilderBaseState.build (package:flutter/src/widgets/async.dart:129:48)
#4 StatefulElement.build (package:flutter/src/widgets/framework.dart:4744:28)
...
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by image resource service ════════════════════════════════════════════════
Invalid argument(s): No host specified in URI file:///gorsel
════════════════════════════════════════════════════════════════════════════════════════════════════
"gorsel" is my unique field key of subcollection document. this error realy makes me tired but really need to use subcollections in my app.
i didnt solved this with codings i just removed all the codes, pages and stuffs recorded to firebase firestore and rewrite them all step by step. i guess i get the reason of the error. it was about navigation time. after i pressed the button named Sinav Oluştur i was expecting the creation of the subcollection named "soru_gorselleri" of new document firstly and then navigation to SinavOlusturPage but all of these were happennig reversely so the Page was returning null. after i did all of them step by step with different RisedButtons , all of errors gone and happy end.
I know that there are already two posts regarding this question, but I could not solve my issue looking at them. Probably because in my case the issue is different.
The code is the following. I want to load some data from the database while showing a loading page. After the data is loaded, I initialize the provider with the loaded data and then I move into a different page.
This code does not need to be in a StatefulWidget, but I try to put it in a StatefulWidget to solve the issue, but without success.
class _InitDBDataState extends State<_InitDBData> {
#override
Widget build(BuildContext context) {
_fetchData(context);
return const Center(child: const CircularProgressIndicator());
}
Future<void> _fetchData(BuildContext context) async {
print('fetching data...');
print('context: $context');
final initData = await DBService.service.getInitialData();
print('Data fetched');
print('context: $context');
Provider.of<DataProvider>(context, listen: false).init(initData);
Navigator.of(context).pushReplacementNamed(MainScreen.routeName);
}
}
I do not have any error if the application runs from scratch, but when I am doing a "Hot Reload" I get the following error pretty often, and it is annoying since I need to restart the application for each small change in the code.
I/flutter ( 9596): fetching data...
I/flutter ( 9596): context: _InitDBData(dirty, state: _InitDBDataState#46860)
I/flutter ( 9596): fetching data...
I/flutter ( 9596): context: _InitDBData(dirty, state: _InitDBDataState#55124)
I/flutter ( 9596): Data fetched
I/flutter ( 9596): context: _InitDBData
E/flutter ( 9596): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.
E/flutter ( 9596): At this point the state of the widget's element tree is no longer stable.
E/flutter ( 9596): To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.
E/flutter ( 9596): #0 Element._debugCheckStateIsActiveForAncestorLookup.<anonymous closure>
package:flutter/…/widgets/framework.dart:3508
E/flutter ( 9596): #1 Element._debugCheckStateIsActiveForAncestorLookup
package:flutter/…/widgets/framework.dart:3522
E/flutter ( 9596): #2 Element.getElementForInheritedWidgetOfExactType
package:flutter/…/widgets/framework.dart:3588
E/flutter ( 9596): #3 Provider.of
package:provider/src/provider.dart:221
E/flutter ( 9596): #4 _InitDBDataState._fetchData
package:productive_diary/initScreen.dart:46
E/flutter ( 9596): <asynchronous suspension>
E/flutter ( 9596): #5 _InitDBDataState.build
I don't know why "fetching data..." is printed twice, and I have no clue on how to solve the issue.
I thought the issue was solved with the solution of Saman Salehi, but working in debug mode I had the same exception in the _fetchData function, that now is called in the function initState()
Exception has occurred.
FlutterError (Looking up a deactivated widget's ancestor is unsafe.
At this point the state of the widget's element tree is no longer stable.
To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.)
I got another error after applying the edits suggested by Stewie Griffin
.
The error is on the line Provider.of<DataProvider>(context, listen: false).init(initData);
I got it during a hot reload. It seems less common than the other error, so the answer of Stewie Griffin surely improved the stability of my Stewie Griffin
E/flutter (23815): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: NoSuchMethodError: The getter 'owner' was called on null.
E/flutter (23815): Receiver: null
E/flutter (23815): Tried calling: owner
E/flutter (23815): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
E/flutter (23815): #1 Provider.of
package:provider/src/provider.dart:193
E/flutter (23815): #2 _InitDBDataState._fetchData
package:productive_diary/initScreen.dart:49
E/flutter (23815): <asynchronous suspension>
E/flutter (23815): #3 _InitDBDataState.initState
Could you please help me?
First of all, never call async methods inside of build as mentioned. Build method is constantly rebuilt and it will cause your fetch method to be repeated like an infinite loop. After you fix that, you still get the same error because of this part:
Navigator.of(context).pushReplacementNamed(MainScreen.routeName);
You shouldn't call Navigator during build. Here is what you need to do:
Add this line to the top of your file to use SchedulerBinding:
import 'package:flutter/scheduler.dart';
Wrap Navigator with SchedulerBinding to wait for completing the state before navigating to another screen. Then, call your async method inside of initState.
class _InitDBDataState extends State<_InitDBData> {
#override
void initState() {
// Call your async method here
_fetchData();
super.initState();
}
Future<void> _fetchData() async {
print('fetching data...');
print('context: $context');
final initData = await DBService.service.getInitialData();
print('Data fetched');
print('context: $context');
Provider.of<DataProvider>(context, listen: false).init(initData);
// Wrap Navigator with SchedulerBinding to wait for rendering state before navigating
SchedulerBinding.instance.addPostFrameCallback((_) {
Navigator.of(context).pushReplacementNamed(MainScreen.routeName);
});
}
#override
Widget build(BuildContext context) {
return Center(child: CircularProgressIndicator());
}
}
Tip: You don't need to pass the context in a Stateful Widget because you can access it from everywhere.
You shouldn't use the build method for anything other than building UI. build can be called at any time even when it's not on the screen.
I would move the _fetchData to the initState so it wouldn't cause any conflict at the build method.
class _InitDBDataState extends State<_InitDBData> {
#override
void initState() {
super.initState();
_fetchData(context);
}
#override
Widget build(BuildContext context) {
return const Center(child: const CircularProgressIndicator());
}
Future<void> _fetchData(BuildContext context) async {
print('fetching data...');
print('context: $context');
final initData = await DBService.service.getInitialData();
print('Data fetched');
print('context: $context');
Provider.of<DataProvider>(context, listen: false).init(initData);
Navigator.of(context).pushReplacementNamed(MainScreen.routeName);
}
}
Navigator.pushReplacement(context,MaterialPageRoute(builder:(context) => WelcomeScreen()),);
|^| .wrap this code SchedulerBinding.instance!.addPostFrameCallback on above code.
like this below:
SchedulerBinding.instance!.addPostFrameCallback((_) {
Navigator.pushReplacement(
context,
MaterialPageRoute(builder: (context) => WelcomeScreen()),
);
});
Schedule a callback for the end of this frame.
Does not request a new frame.
This callback is run during a frame, just after the persistent frame
callbacks (which is when the main rendering pipeline has been
flushed). If a frame is in progress and post-frame callbacks haven't
been executed yet, then the registered callback is still executed
during the frame. Otherwise, the registered callback is executed
during the next frame.
The callbacks are executed in the order in which they have been added.
Post-frame callbacks cannot be unregistered. They are called exactly
once.
Before:
After
SampleCode Here i use rive: ^0.8.1 dartpackage
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:rive/rive.dart';
void main() {
WidgetsFlutterBinding.ensureInitialized();
runApp(MaterialApp(home: SimpleAnimation()));
}
setdata(BuildContext context) async {
await Future.delayed(const Duration(seconds: 5), () {
SchedulerBinding.instance!.addPostFrameCallback((_) {
Navigator.pushReplacement(
context,
MaterialPageRoute(builder: (context) => WelcomeScreen()),
);
});
});
}
class SimpleAnimation extends StatelessWidget {
const SimpleAnimation({Key? key, this.loading}) : super(key: key);
final bool? loading;
#override
Widget build(BuildContext context) {
setdata(context);
return Scaffold(
body: Center(
child: Container(
height: 200,
width: 200,
child: RiveAnimation.network(
'https://cdn.rive.app/animations/vehicles.riv',
),
),
),
);
}
}
class WelcomeScreen extends StatelessWidget {
const WelcomeScreen({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: Center(
child: Container(
child: Text(
"HOME PAGE",
style: TextStyle(fontSize: 50),
),
),
),
);
}
}
if it is caused by accessing ScaffoldMessenger by context then putting it inside a try catch will resolve context error.
try{
ScaffoldMessenger.of(_scaffoldKey.currentContext!).showSnackBar();
} catch(e){
print(e);
}
For this probleme you can use one of this two solutions :
first: add scheduler like this :
SchedulerBinding.instance!.addPostFrameCallback((_) {
Navigator.of(context).pushReplacementNamed(MainScreen.routeName);
});
second: add future delayed with some milliseconds like this :
Future.delayed(Duration(microseconds: 200))
.then((value) {
Navigator.of(context).pushReplacementNamed(MainScreen.routeName);
});
!!! But if you a lot of change of state in the same time this solutions may still give the same error.
if is the case try to use the second solution by augmenting the duration.
I'm trying to inject instances of services (that have been created in the same tree level) into another provider. But down the tree when accessing the provider, I get ProviderNotFoundException exception.
In the following code NotificationService depends on AuthService. Which needs to be passed in the constructor. Hence I inject it using Consumer and Provider.value as mentioned in the docs: https://pub.dev/documentation/provider/latest/provider/Consumer-class.html
Here is the pseudo-code:
return MultiProvider(
providers: [
Provider<AuthService>(
create: (ctx) => AuthService(_storage),
dispose: (ctx, v) => v.dispose(),
),
Consumer<AuthService>(
builder: (context, v, child) {
return Provider.value(
value: Provider<NotificationService>(
create: (ctx) => NotificationService(v),
dispose: (ctx, v) => v.dispose(),
),
child: child
);
},
)
],
child: MyApp()
);
Somewhere down the tree line, When trying to access the NotificationService instance, I get ProviderNotFoundException:
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
final NotificationService _ns = Provider.of<NotificationService>(context);
}
}
Error:
I/flutter ( 4614): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 4614): The following ProviderNotFoundException was thrown building MyApp(dirty, dependencies:
I/flutter ( 4614): [_DefaultInheritedProviderScope<AuthService>]):
I/flutter ( 4614): Error: Could not find the correct Provider<NotificationService> above this MyApp Widget
I/flutter ( 4614):
I/flutter ( 4614): To fix, please:
I/flutter ( 4614):
I/flutter ( 4614): * Ensure the Provider<NotificationService> is an ancestor to this MyApp Widget
I/flutter ( 4614): * Provide types to Provider<NotificationService>
I/flutter ( 4614): * Provide types to Consumer<NotificationService>
I/flutter ( 4614): * Provide types to Provider.of<NotificationService>()
I/flutter ( 4614): * Ensure the correct `context` is being used.
I/flutter ( 4614):
I don't fully understand this, and I'm pretty sure there is a mistake in the above code. What am I doing wrong?
The way you used Provider.value is invalid. But you don't actually need Consumer+Provider. You can do:
MultiProvider(
providers: [
Provider(create: (_) => A()),
Provider(create: (context) => B(Provider.of<A>(context, listen: false)),
],
)