a Flutter beginner here so if my question is stupid don't mind it...
How can I convert a Stream to a Future?
I have a Stream that just calls the requested URL multiple times because it's a Stream. I want to be able to get the data and not the loading state... Because I always just get loading forever
Is there something like Future.fromStream() function somewhere and I'm missing it?
Can I achieve this?
I didn't provide any code because I think it's not needed if you need the code, I can edit the question
Stream has firstWhere method, this will return Future
_profileService.profileStream.firstWhere((element) => false);
Stream and Future are two different concepts.
As you are using, stream is keeping the data updated, and Future is just one time.
Example of using stream: Shopping Cart, listing of items
Example of using future: getUserDetails after login.
If you're using stream, then you can use streambuilder to build your UI
StreamBuilder<User>(
stream: userBloc.author, // your stream here
builder:
(BuildContext context, AsyncSnapshot<User> snapshot) {
if (snapshot.connectionState == ConnectionState.active && snapshot.hasData) {
// do your work here
} else {
return CircularprogressIndicator();
}
},
)
Related
I am using bloc. But I found very rare issue i.e Stream is working well on one page but at the same time when we navigate to another page it is showing in ConnectionState.waiting
Here is my piece of code:
In bloc:
late StreamController<String> _timeRemainingController=StreamController.broadcast();
Stream<String> get timeRemainingStream => _timeRemainingController.stream;
// While adding value:
_timeRemainingController.add("");
Here is streambuilder which I am using
StreamBuilder<String>(
stream: _clockTimerBloc.timeRemainingStream,
builder: (context, snapshot) {
if (snapshot.hasData) {
//code
}
Common code which used everywhere. I am stuck there Please try to check. And thanks for any response.
i am working on flutter project Apply Getx and MVC Arcitecture but when i am getting stream from firestore first it got null values but when hot reload on that page values will goes in to place how to remove this Error, Almost in All type of modules I have to face this Error.
I am trying init State but Ui build first than function in Init State.
It is quite normal for StreamBuilders or FutureBuilders to call their builder function with null values.
The reason is that the build function may be called at any time, irrespective of the stream or future's state.
You should use the hasData property of the snapshot to check for valid data, and handle the case of null data, e.g. by returning a SizedBox widget.
StreamBuilder(
stream: yourStream,
builder: (context, snapshot) {
if (snapshot.hasData) {
return yourWidget();
} else {
return const SizedBox();
}
},
);
I'm trying get a callback after my context build, i already tried with "WidgetsBinding.instance!.addPostFrameCallback", but not works because i have a StreamBuilder and the first load of snapshot data it is null.
I expected exists a callback of StreamBuilder after data completely load and build loaded, here is my code:
StreamBuilder(
stream: this.paymentInfoFormPresenter.key,
builder: (context, snapshot) {
final _formKey = snapshot.data;
if (_formKey == null) {
return Container();
}
return Text('example');
}
);
And i don't find anything about on internet... i hope someone can help me.
To resolve this issue, i needed change the "Text('example')" to an external widget, and added "WidgetsBinding.instance!.addPostFrameCallback" inside of this external widget
So I have Flutter Connectivity Stream.
var subscription = Connectivity().onConnectivityChanged;
And 2 Pages (Tabs) in which I have one StreamBuilder. For some reason, I can't use the same stream with 2 builders (for the first time it works but after I switch tab other StreamBuilder doesn't receive any data)
I tried making 2 separate Connectivity Streams it didn't work.
StreamBuilder(
stream: subscription,
builder: (BuildContext cntx,
AsyncSnapshot<ConnectivityResult> snapShot) {
if (!snapShot.hasData) return CircularProgressIndicator();
var result = snapShot.data;
switch (result) {
case ConnectivityResult.none:
CASE WITHOUT NETWORK
case ConnectivityResult.wifi
CASE WITH NETWROK
default:
}
}
)
I have 2 tabs like that for a different purpose.
From what I understand, you'd like when you subscribe to the stream to get the last value it emitted. A Stream does not emit its current value if you subscribe to it again. If that is indeed what you want to do, you need to use BehaviorSubject.
I want to populate my lists by making API calls when moving to a screen in flutter. I tried calling the async function in the init state however it takes time to load the data of course, and that leads to a null error.
I tried using a future builder in my view. However, I want to make multiple API calls and I don't think that is possible with one future builder. And I would like to avoid having different future builders for each list.
Is there a neat way to do this?
Also is it advisable to load data and pass it on from the previous screen.. since I would like to avoid the loading time?
current code
FutureBuilder(
future: getAllData,
initialData: [],
builder: (context, snapshot) {
if (!snapshot.hasData || snapshot.data.isEmpty) return Center(child: CircularProgressIndicator(valueColor: new AlwaysStoppedAnimation<Color>(Colors.red),));
else {
return createNewTaskView(context, snapshot.data);
}
}),
init method
#override
void initState() {
this.getAllData = getSocieties();
}