I am using GetX and Firebase Realtime Database. When I use this in my GetX controller, and Update a certain value (like the username), the Obx widget in my main screen is updated. Everything works smoothly.
Rx<List<FrediUser>> frediUser = Rx<List<FrediUser>>([]);
String get username => frediUser.value.first.username;
#override
void onInit() async {
super.onInit();
User? user = Get.find<AuthController>().user;
String uid = user!.uid;
frediUser.bindStream(DatabaseManager().frediUserStream(uid));
ever(frediUser, everCalled);
}
But I only have one current user which I want to fetch, so making it a list is unnecesary. If I take the list off like so:
Rx<FrediUser?> frediUser = Rx<FrediUser?>(null); it stops working.
Of course I modify the subsequent lines to adjust for this. Or if I am using a custom class it doesn't notice the update.
Note: The stream is called (checked with a print statement), but it is as if the update never gets to the controller or the UI.
It seems as if the value is nullable, the ever function is not called.
Related question: here
Change it to the following:
Rxn<FrediUser> frediUser = Rxn<FrediUser>();
String get username => frediUser.value.first.username;
Related
I have two drop downs, and I want to do things when they get values selected. One of those is to change the second buttondrop items based on what's selected in the first dropdown.
For example:
Dropdown1 is a list of car manufactuers
Dropdown2 is a list of their models
Dropdown1 selects mercedes
Dropdown2 gets "E Class, S Class" etc
Dropdown1 selects lexus
Dropdown2 gets "ES, LS", etc
(Eventually the second drop down will update a listview as well, but haven't gotten to that yet.)
Data wise, it works, I update the list. The problem is the UI won't update unless I do a hot reload
Currently I am just having the dropdowns fetch their data and using Future builders
Future? data1;
Future? data2;
void initState(){
super.initState();
data1 = _data1AsyncMethod();
data2 = _data2AsyncMethod();
}
_data2AsyncMethod([int? item1_id]) async{
if(item1_id == null){
item2Classes = await DefaultItems().getAllItem2Classes();
listOfItem2ClassNames = DefaultItems().returnListOfItemClassNames(item2Classes);
}
else{
// The methods below calls the DefaultItems methods which have Futures all in them.
// The getAllItems calls a network file with GET methods of future type to get data and decodes them, etc.
// They build a list of the object type, ex List<Item2>
item2Classes = await DefaultItems().getAllItem2Classes(item1_id);
listOfItem2ClassNames = DefaultItems().returnListOfItemClassNames(item2Classes);
}
}
I have this Future Builder nested in some containers and paddings
FutureBuilder{
future: data2,
builder: (context, snapshot){
if(snapshot.connectionState != done...)
// return a circle progress indictator here
else{
return CustomDropDown{
hintText: 'example hint'
dropDownType: 'name'
dropDownList: listOfItem2ClassNames
dropDownCallback: whichDropDown,
}
The onChanged in CustomDropDown passes the dropDownType and the dropDownValue
The callback
whichDropDown(String dropDownType, String dropDownValue){
if(dropDownType == 'item1'){
//so if the first dropdown was used
// some code to get item_1's id and I call the data2 method
_data2AsyncMethod(item1_id);
}
Again the data updates (listOfItem2ClassNames) BUT the UI won't update unless I hot reload. I've even called just setState without any inputs to refresh but doesn't work
So how do I get the UI to update with the data, and is my solution too convoluted in the first place? How should I solve? StreamBuilders? I was having trouble using them.
Thanks
If you do a setState in the whichDropDown function, it will rebuild the UI. Although I'm not exactly sure what you want, your question is really ambiguous.
whichDropDown(String dropDownType, String dropDownValue){
if(dropDownType == 'item1'){
//so if the first dropdown was used
// some code to get item_1's id and I call the data2 method
_data2AsyncMethod(item1_id).then((_) {
setState(() {});
});
}
}
I notice a couple things:
nothing is causing the state to update, which is what causes a rebuild. Usually this is done explicitly with a call to setState()
in whichDropdown(), you call _data2AsyncMethod(item1_id), but that is returning a new Future, not updating data2, which means your FutureBuilder has no reason to update. Future's only go from un-completed to completed once, so once the Future in the FutureBuilder has been completed, there's no reason the widget will update again.
You may want to think about redesigning this widget a bit, perhaps rather than relying on FutureBuilder, instead call setState to react to the completion of the Futures (which can be done repeatedly, as opposed to how FutureBuilder works)
A class Object passing from First Screen to the second Screen While on the second screen when the object changed its value, it's also changing the value on first screen.
Code of First Screen. (widget.templateModel is an object class that i am passing to the second screen)
Navigator.push(context,MaterialPageRoute(builder: (context) =>
EditEmojiTextTemplateScreen(templateModel: widget.templateModel,));
Code of Second Screen (On the second screen i am receiving the object and when i am changing the value of widget.templateModel it also changing the value on the first screen for a simple understandable code below i changed the value in initState while in the gif i am changing value in TextFormField)
class EditEmojiTextTemplateScreen extends StatefulWidget {
final TemplateModel templateModel;
EditEmojiTextTemplateScreen({
Key? key,
required this.templateModel,
}) : super(key: key);
#override
State<EditEmojiTextTemplateScreen> createState() =>
_EditEmojiTextTemplateScreenState();
}
class _EditEmojiTextTemplateScreenState
extends State<EditEmojiTextTemplateScreen> {
final SharedPreferences sharedPreferences = sl();
var txtNameController = TextEditingController();
var txtColorController = TextEditingController();
_EditEmojiTextTemplateScreenState();
#override
void initState() {
widget.templateModel.emoji[0].titleTwo = "kdfff"; //here i am changing the value and it also changing the value on first screen and i dont want this behavior of this object
super.initState();
}
Note: This is happening because of widget variable as mentioned in the documentation but i don't know how to prevent this behavior.
package:flutter/src/widgets/framework.dart
The current configuration.
A [State] object's configuration is the corresponding [StatefulWidget]
instance. This property is initialized by the framework before calling
[initState]. If the parent updates this location in the tree to a new
widget with the same [runtimeType] and [Widget.key] as the current
configuration, the framework will update this property to refer to the
new widget and then call [didUpdateWidget], passing the old
configuration as an argument.
Now I see what you are trying to do.
You could initialize a NEW istance of TemplateModel in the InitState of the second screen.
Then, set the new object's properties like this (or write a cleaner method to do that):
newObject.property1 = oldObject.property1;
newObject.property2 = oldObject.property2;
...
Once the user presses the save button, change oldObject's properties again, so that the first page updates.
You might want to take a look at state management to better understand how to approach this kind of problems.
As the other answer suggests, take a look at state management solutions.
Also keep the models immutable by creating them with final fields. Then to modify, create new instances via copyWith()
Please update you code after navigation.then method
template = snapshot.data;
For a simple Email login with OTP code I have a structure as follows.
View
await _signUpCntrl.signUp(email, password);
Controller
_showOtpDialog(email);
_showOtpDialog func
return Get.dialog(
AlertDialog(
So the thing is _showOtpDialog function is inside a controller file. ie. /Controllers/controller_file.dart
I want do something like a blocListener, call the _showOtpDialog from a screen(view) file on signup success. (also relocate the _showOtpDialog to a view file)
Using GetX I have to use one of the builders either obs or getbuilder. Which is I think not a good approach to show a dialog box.
On internet it says Workers are the alternative to BlocListener. However Workers function resides on Controller file and with that the dialog is still being called on the controller file.
As OTP dialog will have its own state and a controller I wanted to put it inside a /view/viewfile.dart
How do I obtain this?
I tried using StateMixin but when I call Get.dialog() it throw an error.
visitChildElements() called during build
Unlike BLoC there's no BlocListener or BlocConsumer in GetX.
Instead GetX has RxWorkers. You can store your response object in a Rx variable:
class SomeController extends GetxController{
final response= Rxn<SomeResponse>();
Future<void> someMethod()async{
response.value = await someApiCall();
}
}
And then right before the return of your widget's build method:
class SomeWidget extends StatelessWidget{
final controller = Get.put(SomeController());
#override
Widget build(BuildContext context){
ever(controller.response, (SomeResponse res){
if(res.success){
return Get.dialog(SuccessDialog()); //Or snackbar, or navigate to another page
}
....
});
return UI();
}
First thing, you will need to enhance the quality of your question by making things more clearly. Add the code block and the number list, highlight those and making emphasize texts are bold. Use the code block instead of quote.
Seconds things, Depends on the state management you are using, we will have different approaches:
Bloc (As you already added to the question tag). By using this state management, you controller ( business logic handler) will act like the view model in the MVVM architecture. In terms of that, You will need to emit a state (e.g: Sent success event). Afterward, the UI will listen to the changes and update it value according to the event you have emitted. See this Bloc example
GetX (As your code and question pointed out): GetX will acts a little bit different. you have multiple ways to implement this:
Using callbacks (passed at the start when calling the send otp function)
Declare a general dialog for your application ( this is the most used when it comes to realization) and calling show Dialog from Bloc
Using Rx. You will define a Reactive Variable for e.g final success = RxBool(true). Then the view will listen and update whenever the success changes.
controller.dart
class MyController extends GetxController {
final success = RxBool(false);
void sendOtp() async {
final result = await repository.sendOTP();
success.update((val) => {true});
}
}
view.dart
class MyUI extends GetView<MyController> {
#override
Widget build(BuildContext context) {
ever(controller.success, (bool success) {
// This will update things whenever success is updated
if (success) {
Get.dialog(AlertDialog());
}
});
return Container();
}
}
I created a list and made it observable by using using getx obs
var msgChat = List.filled(1, UserMessagesModel(), growable: true).obs;
and if i append or add a new to it, it automatically updates in the UI but my problem is that if i using a single value inside the classes of the list it doesn't get updated until i do it for the second time before it updates
socket.on("msg_delivered", (del) {
OfflineDatabaseManager.instance.updateMsgReadData(del).then((value) {
uController.msgChat.forEach((el) {
if (el.msgId == del) {
print(el.msgId);
el.isRead = 'true';
}
});
});
});
my listview is wrap using an Obx widget which makes it work but it doesn't updated if a single value in the class of the list is changed please is there a way to like refresh the list or listview and also i can't use setState(() {}); because an not inside a Statefulbuilder but in a class which extends to getx
class SocketHandler extends GetxController {}
please how do i fix this issue. Thank. Also if you require more explanation then tell me to explain
you can use refresh method like this on your observable, after changing the value:
msgChat.refresh()
if this didn't work, it's probably because you didn't use Obs correctly
please share the Obs part if the problem remains so i can help
I have this ViewModel and a Riverpod provider for it:
final signInViewModelProvider = Provider.autoDispose<SignInViewModel>((ref) {
final vm = SignInViewModel();
ref.onDispose(() {
vm.cleanUp();
});
return vm;
});
class SignInViewModel extends VpViewModelNew {
FormGroup get form => _form;
String get emailKey => _emailKey;
String get passwordKey => _passwordKey;
final String _emailKey = UserSignInFieldKeys.email;
final String _passwordKey = UserSignInFieldKeys.password;
final FormGroup _form = FormGroup({
UserSignInFieldKeys.email:
FormControl<String>(validators: [Validators.required]),
UserSignInFieldKeys.password:
FormControl<String>(validators: [Validators.required])
});
void cleanUp() {
print('cleaning up');
}
void onSubmitPressed(BuildContext context) {
// _saveRegistrationLocallyUseCase.invoke(
// form.control(_self.emailKey).value as String ?? '',
// form.control(_self.passwordKey).value as String ?? '');
}
}
abstract class VpViewModelNew {
VpViewModelNew() {
if (onCreate != null) {
onCreate();
print('creating');
}
}
void onCreate() {}
}
When I navigate to the page that has the signInViewModelProvider, it prints to the console:
flutter: signInPage building
flutter: creating
flutter: cleaning up
Then popping the page from the stack with Navigator.pop() prints nothing.
Then navigating to the page again prints the same 3 lines in the same order.
I expected onDispose to be called after Navigator.pop(), and not when navigating to the page that reads the provider. Why is onDispose being called directly after creation, and not when using Navigator.pop() (when I expected the provider to be disposed of since no other views reference it)?
Edit: I access the provider with final viewModel = context.read<SignInViewModel>(signInViewModelProvider);
I don't need to listen since I don't need to rebuild the page on
change. Is consumer less performant for this?
No, the performance is meaningless, even if it's listening it's not really affecting the performance because as a Provider there is no way to notify (which is not the case with a state notifier or change notifier)
Also if you don't care to listen after the value has been read The auto dispose understand no one is watching it and it disposes, it's better to use context.read when using tap or gestures that modify something
(I realize this is late to the party but maybe it'll help somebody)
The Riverpod docs come out pretty strongly against using read for the reason you said, i.e. performance/rebuilding concerns.
Basically you should always use watch except:
If you want your custom callback function called when it updates (use listen)
If the actual reading is happening asynchronously or in response to user action (like in an onPressed): this is the only time to use read.
If you're having issues with your widgets rebuilding too often, Riverpod has some ways to deal with that that don't involve using read.