Here is my problem: I have an app that has 2 list view.builders. You can imagine the scenario.
within the Stateful widget, we have:
Widget build(ct)
{
and this returns a column widget that has TWO list views.
The problem I have is that one list view changes (or should change) the items in another list view.
So what are my options? To create two Widget build(ct1) and Widget build(ct2)??
Do we do that? How can I communicate changes to ct1?
Oh my goodness, I've tried a lot, even setState etc... nothing works.. Perhaps could someone tell me how I can invoke the page to be refreshed?? That would work.
I keep on finding the answers myself - but for anyone who has this issue, Flutter apparently has evolved... if you are using the latest version, I really believe that SetState() function should work for you.. you just need to use it in the right place.
Related
In Android, every Fragment can partecipate in populating the options menu (aka "appBar actions", in flutter terms) of the activity, using the Fragment.onCreateOptionsMenu callback.
I would like a similar mechanism also in flutter, i.e. that some widgets are able to add buttons ("actions") to the AppBar.
Threads had already been opened on this topic, but none reports a fully functional example and contains solutions to the precise technical problem I encountered.
To do this, I had thought of using the following 'typical' structure:
a StatefulWidget -to which I have given name ScaffoldHandler (ScaffoldHandlerWidget/ScaffoldHandlerState)- which wraps the entire Scaffold, and which uses InheritedWidget so that widgets further down the widgets tree can get a reference to it in an optimal way (using the classic of() method which executes dependOnInheritedWidgetOfExactType()).
ScaffoldHandlerState keeps in a field the actions set by the various children, and supplies them to the app-bar.
a widget that creates the AppBar. In the build() method it gets the actions to be displayed calling ScaffoldHandlerState.of().
mixin ScaffoldChild on State, which applied to a widget gives it the ability to add actions to ScaffoldHandlerState.
Internally, ScaffoldChild executes ScaffoldHandlerState.of() in didChangeDependencies() (to add actions) and in deactivate() (to remove them).
I originally used initState() and dispose() but this did not handle the case where a ScaffoldChild changes position while not being permanently removed from the widgets tree.
The problem I encountered is that ScaffoldAppBar.build is executed before ScaffoldChild.didChangeDependencies, so when the app-bar is created, ScaffoldChild still has to put its actions in ScaffoldHandlerState.
The curious thing is that this problem is due to the simple linear order in which ScaffoldAppBar and ScaffoldChild are inserted in the page: if instead of a top app-bar I want to create a bottom app-bar, the problem is not there because ScaffoldChild.didChangeDependencies would run before ScaffoldAppBar.build.
As a workaround to overcome the problem, I have inserted in ScaffoldChild.didChangeDependencies a call to scaffoldHandler.setState scheduled by WidgetsBinding.instance.addPostFrameCallback(): thus, after the actions have been inserted in ScaffoldHandler, the app-bar is updated with the new actions.
However, this solution seems like a hack to me.
In stackoverflow I see a lot of problems solved with addPostFrameCallback + setState, and sometimes that solution avoids really understanding where it goes wrong; I am interested in understanding if there are better solutions because my purpose, as well as practical, was to better understand the lifecycle of widgets.
Is there a better solution?
This is my code:
DartPad or Gist
(I tried to shorten it as much as possible, but sorry if it's not really short)
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
Basically topic.
I am trying to display an image slider with content that I pull from a db. I'm calling for this data in the initstate method. I have managed to do a couple of workarounds, but none of them seem clean enough. I don't necessarily need to call it from initstate, but I need that it shows up as I open the screen.
Thanks in advance.
If it's an image, you can use a package called blurhash, Google it for more information regarding that.
I understand the "android:initialLayout" element within the xml folder for defining the default layout of an Android homescreen widget. I want to be able to display a "loading your information" on my widget while I am waiting for data...how do I do this. I have tried to display an error message on my widget if there is no connectivity, but it doesn't get past the "android:initialLayout" , so showing code I believe is irrelevant. Correct me if I am wrong please...don't bash me. Any help greatly appreciated!
Yes, the initialLayout is so that your widget displays something before Android has had a chance to call your widget-updating code. This is a great place to put a "Loading..." message.
Once your onUpdate method is called in your widget, that is your chance to get your data. If you have a connectivity problem at that point, you can display an error message at that point. Otherwise, if you successfully get your data, then you can draw you widget with the data.
I'm not sure if I've answered your question, so apologies if I have not. Please clarify a bit more if I have not. The main questions I have are:
Is Android calling your onUpdate function? Log statements can be really helpful for this.
Are you trying to load your data in the background, such as a separate Service, and then reading the results in the widget? Or are you loading the data inside the widget?
Since each ListView is required to have android:id="android:id/list"... how can i make two listviews on two different fragments? .. the OnItemSelectListener seems to listen to events of the other fragment ... plz help
I have the exact same situation... so far, my guess is that this is not possible since the app only takes into account the first ListView created (because android:id="android:id/list" must be unique in app scope) documentation does not state how to have a custom id, therefore my guess is on this case, ListFragment can't be used.