in initState fetchData func is calling that fetchData func as future.delayed(Duration(seconds: 2),(){

Overview

This question covers calling an async function inside

initState

Future.delayed

The Pattern

dartCopy
@override
void initState() {
  super.initState();
  fetchData(); // ✅ Call async function without await
}

Future<void> fetchData() async {
  await Future.delayed(Duration(seconds: 2), () {
    // This runs after 2 seconds
    setState(() {
      _data = 'Loaded!';
    });
  });
}

Why Not Use await in initState?

initState

async

await

dartCopy
// ❌ Wrong — initState cannot be async
@override
Future<void> initState() async {
  super.initState();
  await fetchData(); // Error!
}

// ✅ Correct — call async function, don't await it
@override
void initState() {
  super.initState();
  fetchData(); // Fire and forget (Dart handles it)
}

Full Working Example

dartCopy
class DataScreen extends StatefulWidget {
  @override
  _DataScreenState createState() => _DataScreenState();
}

class _DataScreenState extends State<DataScreen> {
  String _data = '';
  bool _isLoading = true;

  @override
  void initState() {
    super.initState();
    fetchData(); // ✅ Called without await
  }

  Future<void> fetchData() async {
    // Simulate a 2-second API call
    await Future.delayed(Duration(seconds: 2), () {
      if (mounted) { // ✅ Always check mounted before setState
        setState(() {
          _data = 'Data Loaded Successfully!';
          _isLoading = false;
        });
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Data Screen')),
      body: Center(
        child: _isLoading
            ? CircularProgressIndicator()
            : Text(_data, style: TextStyle(fontSize: 20)),
      ),
    );
  }
}

Why Check

textCopy

mounted

?

If the user navigates away before the 2 seconds complete, the widget is disposed. Calling

setState

dartCopy
Future<void> fetchData() async {
  await Future.delayed(Duration(seconds: 2));

  // ✅ Always check mounted before setState after an await
  if (mounted) {
    setState(() => _data = 'Loaded');
  }
}

Future.delayed Signatures

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// With callback — runs the callback after duration
await Future.delayed(Duration(seconds: 2), () {
  setState(() => _data = 'Done');
});

// Without callback — just waits, then continues
await Future.delayed(Duration(seconds: 2));
setState(() => _data = 'Done');

Common initState Async Patterns

dartCopy
@override
void initState() {
  super.initState();

  // Pattern 1: Direct call
  fetchData();

  // Pattern 2: With error handling
  fetchData().catchError((e) => print('Error: $e'));

  // Pattern 3: Using Future.microtask for post-build access
  Future.microtask(() => fetchData());

  // Pattern 4: Using WidgetsBinding for after-frame callback
  WidgetsBinding.instance.addPostFrameCallback((_) => fetchData());
}

When to Use Each Pattern

fetchData()

Future.microtask(fetchData)

addPostFrameCallback(fetchData)

Future.delayed(duration)

Best Practice: Always check

textCopy

if (mounted)

before calling

textCopy

setState

after any

textCopy

await

in a StatefulWidget. This prevents the "setState called on a disposed widget" error.