I’m working with Flutter and trying to use a FutureBuilder to fetch data based on a state managed by the Provider package. The challenge I’m facing is that my Future depends on a state that I can access through Provider.of<MyData>(context).
Here’s the problem:
- I need to initialize the Future in the constructor of my widget, but since the constructor does not have access to the build context, I can’t retrieve the state from the provider.
- If I try to create the Future inside the build method, it gets recomputed every time the widget rebuilds, which is not ideal for performance.
My Current Approach:
class MyWidget extends StatelessWidget {
final Future<DataType> future;
MyWidget() : future = fetchData(); // This can't access context
@override
Widget build(BuildContext context) {
final myData = Provider.of<MyData>(context); // Need to use myData here
// Creating the Future here causes it to recompute on every build
final future = fetchDataBasedOn(myData);
return FutureBuilder<DataType>(
future: future,
builder: (context, snapshot) {
// Build your widget based on snapshot
},
);
}
}
My Question:
How can I manage the Future in a way that it only computes once, and still be able to access the provider’s state? Is there a recommended pattern for achieving this with Flutter’s FutureBuilder and Provider?
Any suggestions or examples would be greatly appreciated!
1
You can use initState, initState is used to initialize the Future only once when the widget is created.
example :
Future<DataType>? future;
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((callback) {
final data = Provider.of<YourProvider>(context);
setState(() {
future = fetchData(data);
});
});
}
then use the future in the FutureBuilder that you use.
1
class MyWidget extends StatefulWidget {
@override
_MyWidgetState createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
Future<DataType> future;
@override
void didChangeDependencies() {
super.didChangeDependencies();
// Initialize the future in
didChangeDependencies
future = fetchDataBasedOn(Provider.of<MyData>(context, listen: false));
}
@override
Widget build(BuildContext context) {
return FutureBuilder<DataType>(
future: future,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return CircularProgressIndicator();
} else if (snapshot.hasError) {
return Text('Error: ${snapshot.error}');
} else {
return Text('Data: ${snapshot.data}');
}
},
);
}
}
You may use like this, I hope this may help you.
2
> you can use init() method to manage future and it compute only once and also you can access provider state.
- example for understanding..
/// Create getter and future variable
Demo get demoData => Provider.of(context, listen: false);
late Future<dynamic> future;
/// call getData() method
void initState() {
super.initState();
getData();
}
/// in this method you can initialized futureVariable and also manage provider state and you can use future in futureBuilder alse
getData() async {
future = await fetchData(demoData);
}
2