I have class which will fetch the data from an API and store the result in a LIST and display the content in my text widget. When I hot reload it's displaying 'Default'. But is working fine when just reload again though I guard the text widget against the NULL.
The following is my code:
class Sample extends StatefulWidget {
#override
SampleState createState() => SampleState();
}
class SampleState extends State<Sample> {
var selected = [];
#override
void initState() {
super.initState();
callAsyncFetch();
}
callAsyncFetch() async {
var url = 'http://10.0.2.2/abc.php';
var response = await http.get(url);
var jsonData = json.decode(response.body);
print(jsonData);
for (var u in jsonData) {
if (u.substring(0, 2) == 'ABC') {
selected.add(u);
}
}
for (var u in selected) {
print(u);
}
print(selected.length); // working fine
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: Column(children: [
selected.isEmpty
? CircularProgressIndicator()
: new Text(selected[0].toString()),
// i have tried this also but no luck
new Text(selectedStudentsIT.length!=0?selectedStudentsIT[0].toString():'Default Value'),
]),
),
);
}
}
There is simple issue is that, in hot reload it will not run initState again. you can check it by printing something in initState, while in full reload it will call initState.
i think you want to display data when you get response from api.
i think this can be easily achieved by calling setState at the end of callAsyncFetch function, so when you get data from server then it will update ui.
Related
I'm trying to use the hive db to store simple objects in an app that has 3 main pages, selected with a nav bar in the following form (following closely the example from the flutter docs).
/// determine body widget ie page to be rendered
int _pageIndex = 0;
/// list of body widgets
static const List<Widget> _pageOption = [
KeyList(), //index 0
PersonalKey(), //index 1
Crypt(), //index 2
];
/// [index] tells body of scaffold what widget to render
void _changePage(int index) {
setState(() {
_pageIndex = index;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
widget.title,
style: const TextStyle(color: cyan),
),
),
body: Center(
child: _pageOption.elementAt(_pageIndex),
),
I'm not sure how to get the hive box to open / work with each page. for instance a Box would need to used in the KeyList() page. I tried passing the box through state but this is warned against and didn't work.
I tried varies combinations of an async main function and an overriden innitState function in _KeyListState() and now I'm not getting any widgets to render.
main function (from main.dart)
void main() async {
await Hive.initFlutter();
await Hive.openBox<ContactKey>('contacts');
Hive.registerAdapter(ContactKeyAdapter());
runApp(const MyApp());
}
reference from key_list.dart
class _KeyListState extends State<KeyList> {
late final Box contactBox;
#override
void initState() {
super.initState();
contactBox = Hive.box("contacts");
// makeKeyList();
}
#override
void dispose() {
Hive.close();
super.dispose();
}
final List<ContactKey> _keys = []; // = [
// ContactKey(contactName: "cade", publicKey: "123")
// ];
void addKey(String name, String key) async {
ContactKey newContact = ContactKey(contactName: name, publicKey: key);
setState(() {
contactBox.add(newContact);
makeKeyList();
});
}
void makeKeyList() {
if (contactBox.isNotEmpty) {
for (var i = 0; i < contactBox.length; i++) {
_keys.add(contactBox.getAt(i));
}
}
}
#override
Widget build(BuildContext context) {
return Stack(
...
I'm not getting any errors or warnings but when the app is running I get the error "each child must be laid out only once" A google search on this error made it seem like a flutter bug, but if I remove the Hive code my app renders again.
I'm pretty lost right now and if anyone has any tips or sample apps that use a nav bar with hive they'd be greatly appreciated!
Thanks
This is what I'm trying to achieve using flutter GetX package but not working properly.
I have a Firestore document, if the document is changed I want to call an api and keep the data up to date as observable.
The code below seems to work but initial screen shows null error then it shows the data.
I don't know how I can make sure both fetchFirestoreUser() and fetchApiData() (async methods) returns data before I move to the home screen.
GetX StateMixin seems to help with async data load problem but then I don't know how I can refresh the api data when the firestore document is changed.
I'm not sure if any other state management would be best for my scenario but I find GetX easy compared to other state management package.
I would very much appreciate if someone would tell me how I can solve this problem, many thanks in advance.
Auth Controller.
class AuthController extends SuperController {
static AuthController instance = Get.find();
late Rx<User?> _user;
FirebaseAuth auth = FirebaseAuth.instance;
var _firestoreUser = FirestoreUser().obs;
var _apiData = ProfileUser().obs;
#override
void onReady() async {
super.onReady();
_user = Rx<User?>(auth.currentUser);
_user.bindStream(auth.userChanges());
//get firestore document
fetchFirestoreUser();
//fetch data from api
fetchApiData();
ever(_user, _initialScreen);
//Refresh api data if firestore document has changed.
_firestoreUser.listen((val) {
fetchApiData();
});
}
Rx<FirestoreUser?> get firestoreUser => _firestoreUser;
_initialScreen(User? user) {
if (user == null) {
Get.offAll(() => Login());
} else {
Get.offAll(() => Home());
}
}
ProfileUser get apiData => _apiData.value;
void fetchFirestoreUser() async {
Stream<FirestoreUser> firestoreUser =
FirestoreDB().getFirestoreUser(_user.value!.uid);
_firestoreUser.bindStream(firestoreUser);
}
fetchApiData() async {
var result = await RemoteService.getProfile(_user.value!.uid);
if (result != null) {
_apiData.value = result;
}
}
#override
void onDetached() {}
#override
void onInactive() {}
#override
void onPaused() {}
#override
void onResumed() {
fetchApiData();
}
}
Home screen
class Home extends StatelessWidget {
const Home({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Container(
child: Obx(() =>
Text("username: " + AuthController.instance.apiData.username!))),
),
);
}
}
To be honest, I never used GetX so I'm not too familiar with that syntax.
But I can see from your code that you're setting some mutable state when you call this method:
fetchApiData() async {
var result = await RemoteService.getProfile(_user.value!.uid);
if (result != null) {
_apiData.value = result;
}
}
Instead, a more robust solution would be to make everything reactive and immutable. You could do this by combining providers if you use Riverpod:
final authStateChangesProvider = StreamProvider.autoDispose<User?>((ref) {
final authService = ref.watch(authRepositoryProvider);
return authService.authStateChanges();
});
final apiDataProvider = FutureProvider.autoDispose<APIData?>((ref) {
final userValue = ref.watch(authStateChangesProvider);
final user = userValue.value;
if (user != null) {
// note: this should also be turned into a provider, rather than using a static method
return RemoteService.getProfile(user.uid);
} else {
// decide if it makes sense to return null or throw and exception when the user is not signed in
return Future.value(null);
}
});
Then, you can just use a ConsumerWidget to watch the data:
#override
Widget build(BuildContext context, WidgetRef ref) {
// this will cause the widget to rebuild whenever the auth state changes
final apiData = ref.watch(apiDataProvider);
return apiData.when(
data: (data) => /* some widget */,
loading: () => /* some loading widget */,
error: (e, st) => /* some error widget */,
);
}
Note: Riverpod has a bit of a learning curve (worth it imho) so you'll have to learn it how to use it first, before you can understand how this code works.
Actually the reason behind this that you put your controller in the same page that you are calling so in the starting stage of your page Get.put() calls your controller and because you are fetching data from the API it takes a few seconds/milliseconds to get the data and for that time your Obx() renders the error. To prevent this you can apply some conditional logic to your code like below :
Obx(() => AuthController.instance.apiData != null ? Text("username: " + AuthController.instance.apiData.username!) : CircularProgressIndicator())) :
I'm trying to use a GetX Builder in combination with a bool in the controller to display a loading spinner while fetching data and then the data afterwards.
Printing the update to the bool shows it finishes loading and changes the variable but the UI is never updated to reflect this.
Controller
class AuthController extends GetxController {
//final RxBool isLoading = true.obs;
//var isLoading = true.obs;
final Rx<bool> isLoading = Rx<bool>(true);
setLoading(bool status) {
isLoading.value = status;
print(isLoading.value);
update();
}
fetchUserData() async {
setLoading(true);
_firebaseUser.bindStream(_auth.authStateChanges());
if (_auth.currentUser != null) {
bool profileRetrieved =
await FirestoreDB().getUserProfile(_auth.currentUser!.uid).then((_) {
return true;
});
setLoading(!profileRetrieved);
}
}
}
Profile Page
class ProfileCard extends StatelessWidget {
const ProfileCard({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return GetBuilder<AuthController>(
init: AuthController(),
initState: (_) => AuthController().fetchUserData(),
builder: (controller) {
if (controller.isLoading.value) {
return const Center(child: CircularProgressIndicator());
}
return Container(...);
},
);
}
}
That widget is called within another as part of the wider UI. Let me know if you'd need to see that and/or anything else.
As you can see I've tried different ways of setting up the bool and none of them seem to trigger a change of UI in the builder.
Probably doing something stupid but I've tried a few different approaches and looked around for people having similar problems but not been able to crack it.
Thanks in advance.
You are using isLoading as a Rx<bool>. In that case you need to change GetBuilder into GetX. And no need to call update().
GetBuilder is for non-reactive, non-Rx, simple state management
GetX is for reactive, Rx state management
I am new to the Flutter GetX package and facing problem when using the flutter GetX package. I have several app screens where one screen for listing all the products from the database.
In my product controller, I am fetching all the data from the database and showing with listview like as given code below and It's working fine.
Problem: When I'm inserting a new record from another controller and come back to the product list controller it'll not showing newly added data. Actually this time onInit method won't fire.
Controller code
class ProductIndexCtrl extends GetxController {
var products = [].obs;
#override
void onInit() {
super.onInit();
getAll();
}
void getAll() {
Product.getAll().then((jsonList) {
products.value = Product.fromJsonList(jsonList);
});
}
}
class ProductCreateCtrl extends GetxController {
void saveData(Product product) {
...
...
//after successful insert
Get.toNamed('productIndex');
}
}
Product index screen
final ctrl = Get.put(ProductIndexCtrl());
GetX<ProductIndexCtrl>(builder: (controller) {
return _listview(controller.products);
}
Widget _listview(data) {
...
...
}
As the GetX dependency manager controls the lifecycle of dependencies, you should not manually call them. It's GetX's responsibility when to call them.
Therefore you need to manually call getAll() method of your ProductIndexCtrl controller inside the saveData() method of your ProductCreateCtrl like:
saveData(Product product){
....
....
final indexCtrl= Get.find<ProductIndexCtrl>();
indexCtrl.getAll();
}
By returning to that page, you can return the new information locally to the previous page
> Controller code
class ProductIndexCtrl extends GetxController {
var products = [].obs;
#override
void onInit() {
super.onInit();
getAll();
}
void getAll() {
Product.getAll().then((jsonList) {
products.value = Product.fromJsonList(jsonList);
});
}
}
> Product index screen
class ProductCreateCtrl extends GetxController {
void saveData(Product product) {
...
...
//after successful insert
Get.back(result: product);
}
}
and get Data when back
Get.toName('ProductCreateCtrl').then(result){
products.add(result);
}
I tried a similar thing with one single controller. The code snippet is given below.
First, create the ProductView. Since this is the entry point of the application, So you will create a GetX controller inside of this.
/// THIS IS PARENT VIEW SO WE WILL CREATE GETX CONTROLLER HERE
class ProductView extends StatelessWidget {
const ProductView({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
final controller = Get.put(ProductController());
return Scaffold(
appBar: AppBar(
title: const Text('Products'),
),
body: Obx(() {
return controller.myProductList.isEmpty
? showNoProductView()
: ListView.builder(
itemCount: controller.myProductList.length,
itemBuilder: (context, index) {
return YourListItemView(controller.myProductList[index]);
},
);
}),
);
}
}
The view AddProductView is responsible for adding new products to the DB. We can assume that there is a FloatingActionButton present in ProductView and onClick on that button, we will open this AddProductView.
/// THIS IS CHILD VIEW SO WE WILL FIND THE PRODUCT CONTROLLER HERE
class AddProductView extends StatelessWidget {
const AddProductView({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
final controller = Get.find<ProductController>();
return Scaffold(
appBar: AppBar(
title: const Text('Add Product'),
),
body: Column(
children: [
// ADD YOUR OTHER WIDGETS TO GET PRODUCT INFO
TextButton(
child: const Text('Click to Add'),
onPressed: () {
var productName = nameTextEditingController.text;
var productQuantity = qtyTextEditingController.text;
var product = YourProductObject(productName, productQuantity);
controller.addProduct(product: product);
},
)
],
),
);
}
}
Finally, the controller will look like this.
import 'package:get/get.dart';
class ProductController extends GetxController {
// this will be your custom product list object
var myProductList = <YourProductObject>[].obs;
var dbInstance = YourDbInstance();
#override
void onReady() async {
super.onReady();
// perform database operation
await fetchDataFromDb();
}
Future<void> fetchDataFromDb() async {
// assuming that data is coming as List<YourProductListObject>
// always use try catch in db operation. for demo purpose I am skipping that.
var productListFromDb = await dbInstance.getYourProductListObjectList();
myProductList.assignAll(productListFromDb);
}
Future<void> addProduct({required YourProductObject product}) async {
// assuming that there is a function that returns true if a product is added to db
var isAdded = await dbInstance.addProduct(product);
if (isAdded) {
myProductList.add(product);
}
}
}
Since myProductList is a RxList so getx will observe it and will update the UI accordingly. You must add Obx((){}) in view.
Please check out this 36 seconds video for more clarity, cause it was getting too verbose explaning things : https://www.youtube.com/watch?v=W6WdQuLjrCs
My best guess
It's due to the provider.
App structure ->
Outer Page -> NoteList Page
The Outer Page code :
class OuterPage extends StatefulWidget {
#override
State<StatefulWidget> createState() {
return OuterPageState();
}
}
class OuterPageState extends State<OuterPage> {
final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
int _selectedTab = 0;
var noteList;
final _pageOptions = [
NoteList(),
AnotherPageScreen(),
];
#override
Widget build(BuildContext context) {
var noteProvider = Provider.of<NotesProvider>(context, listen: false);
var customFabButton;
if (_selectedTab == 0) {
customFabButton = FloatingActionButton(
// Password section
onPressed: () {
navigateToDetail(context, Note('', '', 2), 'Add Note');
},
child: Icon(Icons.add),
);
~~~ SNIP ~~~
The Notes Tab aka NoteList page code :
class NoteList extends StatefulWidget {
NoteList();
#override
NoteListState createState() => NoteListState();
}
class NoteListState extends State<NoteList> {
final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
List<Note> noteList;
int count = 0;
#override
Widget build(BuildContext context) {
Provider.of<NotesProvider>(context).getNotes();
return Scaffold(
key: _scaffoldKey,
body: Provider.of<NotesProvider>(context).count > 0
? NoteListScreen(_scaffoldKey)
: CircularProgressIndicator());
}
}
For full code : check here : https://github.com/LuD1161/notes_app/tree/reusable_components
Update 1 - Possible solution is FutureBuilder
I know that there's a possible solution with FutureBuilder but I think even Provider is apt for this use case.
Moreover is it an anti-pattern here ?
Also, please don't suggest another package for the same thing, if possible try limiting the solution to Provider or base libraries.
Update 2 - Not possible with FutureBuilder
FutureBuilder can't be used here because there's a delete button in the list tile and hence when the note gets deleted the note list won't get updated.
The issue is coming because of the getNotes function you are calling from build method. You are calling notifyListeners from that function. It again re-builds the widget and calls the build method again and this cycle continues.
You either need to set false to the listen property of provider, but it will break your functionality. To fix this, you have to move the getNotes call from build function to initState like following:
#override
void initState() {
super.initState();
postInit(() {
Provider.of<NotesProvider>(context).getNotes();
});
}
Implement postInit (Reference: Flutter Issue 29515):
extension StateExtension<T extends StatefulWidget> on State<T> {
Stream waitForStateLoading() async* {
while (!mounted) {
yield false;
}
yield true;
}
Future<void> postInit(VoidCallback action) async {
await for (var isLoaded in waitForStateLoading()) {}
action();
}
}
Note: Instead of writing the postInit code, you can also use after_init package for same purpose.
Several other posts discussing similar kind of issues:
How to correctly fetch APIs using Provider in Flutter
Using provider in fetching data onLoad