I am writing an app that is making use of Cubits for state management. It is an audiobook player and you can look up the different audiobooks and display them. Then jump to the author or the series and explore around your library.
As it stands at the moment the different pages you move between are being rendered using a BLoC builder as follows.
class ScreenSelector extends StatelessWidget {
#override
Widget build(BuildContext context) {
return BlocBuilder<ScreenCubit, ScreenState>(builder: (context, state) {
if (state is HomeScreenState) {
return HomeScreen();
}
if (state is BookScreenState) {
return BookScreen(bookId: state.bookId);
}
return null;
});
}
}
There are genre, author and series screens as well that will work the same as the book screen. There is a cubit that is emitting the appropriate state hooked up to different clickable widgets on the home and book page. This all works as expected. There is also an authorization flow that is worked to either render the HomeScreen or go to the Loginscreen. This also works nicely.
But i'd like to use a navigator instead so you can go backwards to previous pages. That seems like the right way to navigate but i'm lost on getting Navigator to work with BLoC.
I tried constructing the MaterialPageRoutes and pushing them when the state changes instead of loading the page and I tried converting the BlocBuilder to a BlocListener. Trying to push the page in the BlocBuilder did nothing and the BlocListener would only ever throw an exception.
If anybody has a pointer to how I might go about doing this or knows of a simple example of using Cubits with Navigator 1.0 in flutter I would be most grateful. I looked around but all of the examples I found either mixed in an authorization example and I got lost.
I expect i'm approaching the problem incorrectly but i'm not sure where I have gone off track.
Turns out I just have really crappy GoogleFu and you can find the solution to the problem at
https://bloclibrary.dev/#/recipesflutternavigation
It has a nice recipe that explains it well by the author of Bloc
Related
I am currently trying to build a flutter app using Beamer and Provider. The app should have a BottomNavbar and remember the state of each tab when switching. Currently I am doing that by using nested Beamers with an IndexedStack.
Now I want to have a BeamLocation with multiple pages, that all share a common state. To do that I want to wrap the entire BeamLocation with a ChangeNotifierProvider. However when doing that, the app tries to build a Location of the wrapped BeamLocation after it already is on another BeamLocation. I am pretty sure the issue is with the builder method of BeamLocation:
When overriding it like this:
#override
Widget builder(BuildContext context, Widget navigator) => navigator
It works fine, which is expected since it doesn't really do anything.
But if I change it to this:
#override
Widget builder(BuildContext context, Widget navigator) {
return Container(
child: navigator,
);
}
It tries to build a page of that location, even when a different location from another BeamLocation is already active.
For a container this isn't a problem, but since I am trying to wrap the BeamLocation with a Provider as stated in the documentation, it is. When doing that, the extra build happens after the Provider is already gone, causing an error.
When you pop the navigator too many times in Flutter you are met with a black screen. To prevent that from ever happening to the user because of some unforeseen event on my part, I have created the following function:
static void safePop<T extends Object>(BuildContext context, [T? result]) {
if (Navigator.canPop(context)) {
Navigator.of(context).pop<T>(result);
}
}
That works great for simple pops, but I've recently migrated my app to using named routes and would like to use the Navigator.popUntil(context, ModalRoute.withName()) to more accurately pop widgets when I'm 4 or 5 pages into the app. I'm having trouble figuring out a way to implement something similar to above with popUntil.
Is there a way to prevent the Navigator from popping to a black screen in case of an incorrect/non-existent route being passed to the popUntil function?
Thanks
I'm working on an app that accesses two api's that contain location data that updates regularly (every 5 seconds or so). I want to utilize flutter and flutter_bloc to manage my state, but I'm not sure where the interval would come into play. I understand bloc and how the ui interacts with it with BlocBuilder and BlocProvider, as well as providing a repository that handles the api calls. What I'm not sure about is where to put the interval/timer. My idea was to do a normal bloc setup:
class DataBloc extends Bloc<DataEvent, DataState> {
//constructor
#override
Stream<DataState> mapEventToState(DataEvent event) async* {
if (event is FetchData) {
var data = repository.getData();
yield* _mapFetchDataToState(data);
}
}
}
In the ui:
class MainPage extends StatelessWidget {
#override
Widget build(BuildContext context) {
final dataBloc = BlocProvider.of<DataBloc>(context);
Timer.periodic(fiveSeconds, (Timer t) => dataBloc.add(FetchData()));
return ui stuff
}
}
But I'm not sure if this is the right way to leverage BLoCs and/or timers. But I basically need to call the api on an interval and then have the data update in my ui without a full refresh of all the widgets. They're going to be icons on a google map, and I want the icons to update their locations when the data I pull is updated. How can I accomplish this? For reference, I've looked at the flutter_bloc docs for the timer app here and I thought it was a little overkill and that my idea above was simpler, just not sure if this is the right way. I'm pretty new to flutter so any help would be appreciated.
I'd recomend not to put initializing code inside build. Make it a StatefulWidget and add a dispose method to clear the timer. And inside initState setup the timer.
There's no right way in programming. There are best practices, so as long as it work for your use case is ok.
I would either put the timer into the bloc/cubit because its part of your logic and not of your ui.
Or if you use a repository I would probably use a stream listen to it in your bloc and periodically update the stream in your repo.
But any better suggestions are more than welcome, because I am also looking for some kind of 'the way to do'...
I'm a new Flutter developer and I have a problem, which I haven't been able to solve yet, even if I tried a lot.
I'm developing an App, where at some point a Dialog is opened(with showDialog()). In this Dialog there are 2 AutoCompleteTextField:
In the first one, the data will always be the same. So there is a list and the user needs to choose one of the choices. First AutoCompleteTextField code
In the second one, the data to be shown depends on the previous choice. In other words,
whenever an item from the previous list is chosen, the subdata of the item will be requested. Second AutoCompleteTextField code
The required data is fetched properly, however the dialog is not refreshing state so the suggestions of the second AutoCompleteTextField appears empty. When I close and enter again the suggestions of the second appears as they should.
To get notified when the data changes I use ChangeNotifier and Provider, but doesn´t refresh the Dialog (ChangeNotifier class). I also use StatefulBuilder to be able to use setState, but again, doesn´t refresh (Dialog code).
I would like to know if there is any other way to refresh the Dialog. Thank you!
PD: This is my first question in StackOverflow. I tried my best.
I think you need to use Provider.of(context) to be able to listen to the updates and refresh or add/update the data.
Provider.of(context)
I would create a widget class instead of the _widgetTask function and then use Provider.of(context) inside the widget build function like following (I think you can also try to add it inside the _widgetTask function but I dont know if this would work).
class WidgetTask extends StatelessWidget {
//WidgetTask contructor here..
#override
Widget build(BuildContext context) {
final odooData = Provider.of<OdooData>(context);
And then use the odooData to access the data/functions you need to update/listen to from the provider.
Also you can wrap the widget with GestureDetector so that you can update the widget upon tapping using the OnTap property.
flutterdartdialogrefreshproviderconsumer
I am developing a mobile application using Flutter. I am new to Flutter. I am using BLoC for state management. I know that it is specially designed for management async execution. But also the purpose of BLoC is for state management. But I am a little bit confused and not quite sure how to handle the primary data types in BLoC.
Let's imaging the I have a button and an image. The functionality would be that when the button is clicked, the visibility of the image will be toggled. Literally, we just need to use a boolean variable to manage the state of the image. This is how I would implement it.
I have a bloc class called HomeBloc with the following implementation.
class HomeBloc {
bool _isImageDisplayed = true;
bool get isImageDisplayed => _isImageDisplayed;
void set isImageDisplayed(bool displayed) {
this._isImageDisplayed = displayed;
}
//the rest of the code for other functionalities goes here
}
final homeBloc = HomeBloc();
Then in the HomePage widget, I update the state of the image like this inside the setState method when the button is clicked.
this.setState(() {
homeBloc.isImageDisplayed = false;
});
My question is that "is it the standard way to manage primary data type in the BLoC in Flutter"? Is this the best practice? Do we need to use StreamBuilder? Do we even need to manage it inside the BLoC?
It's not the best practice I guess, as using setState becomes really hard on big applications and re-rendering widgets that don't change for no reason. Imagine making an e-commerce app and you just go to the product page, you add the product you like into the cart, but you have designed in your home page a cart icon with a red dot with a number inside it to specify how much products you got in your cart, so you handle the state of that icon in the main.dart file by passing a function that setState the home page route or maybe the whole application, it's hard, isn't it?.
Thankfully, BLoC and Provider patterns are basically using setState but in a better way so you don't have to re-render the whole page just for a small change in a text or something else, but you just re-render a specific widget in your widget tree.
I also recommend using BLoC Provider which is built on Provider and RxDart (Streams) as it makes great isolation between UI code and business code.
Check Provider and BLoC Provider.