How to get result of FutureBuilder from the parent FutureBuilder? - flutter

Question

The entry point is _processError function. I expect to get a widdet there. And this _processError runs from a parent FutureBuilder.
Then another Future builder should be executed, at least I think it should... But it seems there is no result from there. Whats wrong with it?
FutureBuilder<List<ShortLetter>>(
future: fetchMessages(),
builder: (BuildContext context, AsyncSnapshot<List<ShortLetter>> snapshot) {
...
} else if (snapshot.hasError) {
return _processError(snapshot, context); // I want to get a widget when an error happens
...
},
);
Future<bool> checkConnection() async {
debugPrint('---checkConnection---');
var connectivityResult = await (Connectivity().checkConnectivity());
...
// and returs true or false
}
Widget _processError(AsyncSnapshot snapshot, BuildContext context) {
var errorType = snapshot.error.runtimeType;
debugPrint('AllMessagesView, snapshot error: $errorType');
debugPrint(snapshot.error.toString());
if (errorType == TimeoutException) {
debugPrint('0000000000000000');
//////////////////////////////////////////////////////
// there is any output in console from the FutureBuilder below
// but checkConnection() was executed
FutureBuilder<bool>(
future: checkConnection(),
builder: (BuildContext context, AsyncSnapshot<bool> snapshot) {
if (snapshot.hasData) {
debugPrint('11111111111111 snapshot data: ${snapshot.data}');
if (snapshot.data == true) {
...
}
...
} else if (snapshot.hasError) {
debugPrint('2222222222222');
...
} else {
debugPrint('Error. This should not happen.');
...
}
},
);
...
}
...
}
here is a sample console output and any result from the second FutureBuilder
I/flutter (10556): AllMessagesView, snapshot error: TimeoutException
I/flutter (10556): TimeoutException after 0:00:10.000000: Future not completed
I/flutter (10556): 0000000000000000
I/flutter (10556): ---checkConnection---

Answer 1

Parent FutureBuilder is already been processed, I think we don't need to pass Async data.
This demo widget may help.
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<int> parentF() async {
return await Future.delayed(Duration(seconds: 2), () => 4);
}
Future<String> childF(int sec) async {
return await Future.delayed(Duration(seconds: sec), () => "got the child");
}
Widget childFB(final data) {
print(data.runtimeType);
return FutureBuilder(
future: childF(4),
builder: (context, snapshot) => snapshot.hasData
? Text("${snapshot.data!} parent data: $data ")
: const Text("loading second child"));
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
FutureBuilder(
future: parentF(),
builder: (context, parentSnapshot) {
return parentSnapshot.hasData
? FutureBuilder<String>(
future: childF(3),
builder: (context, snapshot) {
return snapshot.hasData
? Text(
"${snapshot.data!} parent data: ${parentSnapshot.data} ")
: const Text("loading child");
},
)
: const Text("loading parent");
},
),
FutureBuilder(
future: parentF(),
builder: (context, parentSnapshot) {
return parentSnapshot.hasData
? childFB(parentSnapshot
.data) // it already have normal data, not async
: const Text("loading parent");
},
),
],
));
}
}