Here is the problem: I have a list of items displayed in a list view. I can edit these items with the dialogs displayed by clicking on them. After editing and closing the dialog, I also need to update the items on the list view. I'm currently doing this with the following code snippet in my list view item widget:
showDialog(
context: context,
builder: (context) {
return UpdateItemDialog(item: _item);
},
).then((updatedItem) {
if (updatedItem != null) {
setState(() => _item = updatedItem);
}
});
and by calling Navigator.of(context).pop(_item); from my dialog.
It works perfectly fine when there are no rebuilds occur until the dialog is dismissed. However, for example, if the orientation is changed when the dialog is open, I get Unhandled Exception: setState() called after dispose() error since the list view also rebuilt because of the orientation change and the then clause in my code runs on the destroyed widget.
Is there a way to access the rebuilt widget from a destroyed widget?
Or should I use a different approach to this problem?
By the way, changes should only be accepted after the dialog is dismissed, so I should return the item from the dialog.
I believe your best bet would be to introduce even a simple state management solution (Provider would be good) to handle communication between a dialog and other widgets.
Check out the Gist below (Run it on Dartpad.dev) as an example how you can keep it simple, yet clean and decoupled
https://gist.github.com/romanejaquez/8aed8d699fba8fdfff4b0966dfe47663
in which I show that instead of passing data from a dialog back to another widget, a State Management solution would allow you for a decoupled way of passing data back and forth, notifying each other and triggering rebuilds (which is kind of calling setState() since pretty much that's what you want - trigger a rebuild on the other widget. In this example, I'm sending a value back to the originating widget and triggering a rebuild (thanks to the Consumer widget listening to the changes triggered in the common service. That'd be my honest suggestion.
Related
I have a typical CRUD operation task: (List Sites, Add Site, ...)
I created a SitesProvider. In the same provider, I added 2 methods for add and edit. I was thinking to use the same provider in the 2 screens (ListSites and AddEditSite)
In the ListSites screen, it works fine. Here is the problem:
I open the AddSite screen by clicking the AddButton in the ListSites screen
Hit submit (did not enter data, simulating error case)
The error gets displayed in the ListSites screen, not in the AddSite screen.
It makes sense. They both use the same provider, both screens are on the stack. It seems that the first one only consumes the state update and displays the error.
I use MultipleProviders approach that wraps the MaterialApp with all providers in the app.
Can we fix that without creating separate providers for each of the 2 screens?
EDIT:
I used provider.removeListener in the ListSites screen right before I open the AddEdit and it shows the error in the correct screen now. I still have to do some other tweaks to get it back to listen after I add. Not efficient I think but it is a step.
I ended up doing that:
Added Another Field in the provider (stateType: list/addedit)
Change the type per the screen I'm currently in
provider.stateType = UIStateType.add_edit;
await Navigator.push(context,
MaterialPageRoute(builder: (context) => AddEditSiteScreen()));
provider.stateType = UIStateType.list;
in build(), I check for the type
sitesProvider = Provider.of(context);
if (sitesProvider.stateType != UIStateType.add_edit) return Container();
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 struggling with the following problem:
I built a list of widgets using StreamBuilder (and made it searchable). The widgets are Cards and inside them the user can make his selection and then push a button.
Everything is (was) working just fine.
Then I wanted to add a little animation and make the Icon associated to the button an animated one.
Now it is a mess, the StreamBuilder is in an infinite loop and I have also some problem on my list. If I comment out the animated icon and put in again the previous Icon ...everything starts to work fine again.
...
child: FloatingActionButton(
onPressed: (){
addFood();
mealListState.getAcontroller(id).forward();
},
child:
// MyAddIcon(id), //--> my animated Icon. It does not work
Icon(Icons.add), //--> it works
....
I read that the problem is that adding States management (Unnecessary Widget Rebuilds While Using Selector (Provider) inside StreamBuilder) inside the stream mess things up and that you have to make the widget building the stream Stateful and set up the stream in the initState.
I tried to follow this way but I need the context to build my card list, so I could follow the above hint just to read the data from db (firestore) and ...it is not enough
Could someone point me in the right direction or I have to leave the idea and move on?
Thanks
If you need the context, you can try to listen to the the stream in the didChangeDependencies method of your State class.
Use the Streamsubscription returned by stream.listen to cancel your subscription like so to avoid subsribing twice or even more times:
#override
didChangeDependencies() {
final stream = Provider.of<MyStream>(context); // context available here.
if (this.streamsubscription != null) {
this.streamsubscription.cancel();
}
this.streamsubscription = stream.listen((value) {
// your callback code here
});
super.didChangeDependencies(); // important
}
Working on a Flutter app, I am handling deeplinks with a SDK for which I am given a listener that I must handle as soon as the app starts, therefore in the main().
Once a deeplink is received, I must navigate to the proper screen, based on the parameters passed along the deeplink data.
Since I receive the deeplink in the main function, I am detached from the Context of the app, therefore to access the NavigatorState I used a navigation singleton with a GlobalKey passed to my CupertinoApp's navigatorKey. I later use this key to retrieve the NavigatorState and call push. (instead of Navigator.of(context)....
However, if opening the app from a deeplink, it is very likely that the navigatorKey does not contain anything (yet).
How can I detect/wait until the Navigator is ready ?
As of right now my approach is to add a WidgetsBinding.instance.addPostFrameCallback in my App's initState, that resolves a promise to indicate when the GlobalKey pointing to the NavigatorState can be used... I'm sure there is a beter way to achieve this.
For this i make the initialRoute as a Loading screen and execute all my logic inside it , that way i can have different initialRoutes and i don't have to worry about not having MediaQuery, or Navigator, or even ThemeData.
However the question specifies a way to know if the navigator is available, for this i would use the builder function of MaterialApp/WidgetsApp/CupertinoApp, it's used to override the navigator altought i use it to add pading and a global background color and even override the navigator widget with a custom one,
CupertinoApp(
...
builder: (context, child){
//The navigator is ready
Future.delayed(Duration.zero,
() => print(navigatorKey.currentContext)); //We use a delayed since the child needs to be returned first. It's kinda like a hack 7u7
return child;
}
Ok, I am working on a media player app using flutter. Now when I press the play button, it changes to pause button. (Only the icon on the button changes)
The onPressed function for the button changes a boolean value and calls the setState() method.
It goes something like this.
bool _playing = false;
void _onPlayButtonPressed() {
setState () {
if (_playing)
_playing = false;
else
_playing = true;
}
}
I also have a function that returns the icon based on the value of _playing.
Widget _playButtonIcon() {
//This function has no setState() call
if (_playing)
//return pause icon
else
//return play icon
}
Everything works fine. The icon changes everytime I press the button. However as mentioned in docs and also in Flutter Demo App, setState() method calls the build method. Which redraws the entire widget tree including child widgets that are completely unchanged.
Is this approach justified or is this an overkill?
Do I have to put the button on a different Stateful Widget Class and call its build method via setState() everytime I tap this playButton?
What if I have other widgets that also changes the state of UI. Possibly changing different widgets?
What is the proper way to do this without having a performance hit?
Creating a play button that is a widget of its own with a state that maintains whether it is playing or not definitely makes sense. Now when you call setState on the parent widget it does call the build method, but as far as I know it does not necessarily redraw everything from scratch. If no changes are found in some of the embedded widgets it does not redraw them since they are already in the widget tree. Finally, it is okay to call setstate, however if your app starts getting bigger and you find yourself calling set state in too many places, and want to use global keys, I would advise looking into the Provider package, and making use of the ChangeNotifier/Consumer pattern.