is dispose method is called if navigating screen on top of currenting screen then well the previous screen dispose method is called ?

Overview

No — when you push a new screen on top of the current one, the previous screen's

dispose()

dispose()

Navigation Stack Lifecycle

textCopy
Initial State:
Stack: [HomeScreen]
→ HomeScreen.initState() called ✅
→ HomeScreen.build() called ✅

Push new screen:
Stack: [HomeScreen, DetailScreen]
→ DetailScreen.initState() called ✅
→ DetailScreen.build() called ✅
→ HomeScreen.dispose() called? ❌ NO! HomeScreen is STILL in stack

Pop back:
Stack: [HomeScreen]
→ DetailScreen.dispose() called ✅ (removed from stack)
→ HomeScreen.build() called again (receives focus)
→ HomeScreen.dispose() called? ❌ Not yet (still in stack)

Pop HomeScreen (or replace with pushReplacement):
Stack: []
→ HomeScreen.dispose() called ✅

Code Example

dartCopy
class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  @override
  void initState() {
    super.initState();
    print('HomeScreen: initState'); // Called once on push
  }

  @override
  void dispose() {
    print('HomeScreen: dispose'); // Called when POPPED
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: () {
        Navigator.push(context, MaterialPageRoute(
          builder: (_) => DetailScreen(),
        ));
        // HomeScreen is NOT disposed — just covered
      },
      child: Text('Go to Detail'),
    );
  }
}

When is dispose() Called?

Navigator.push()

Navigator.pop()

Navigator.pushReplacement()

Navigator.pushAndRemoveUntil()

Navigator.popUntil()

Lifecycle During Push/Pop

dartCopy
// What actually happens with widget state:
Navigator.push → previous widget deactivated (not disposed)
              → new widget mounted

Navigator.pop  → current widget dispose() is called
             → previous widget reactivated

Practical Implication

dartCopy
class _HomeScreenState extends State<HomeScreen> {
  StreamSubscription? _subscription;

  @override
  void initState() {
    super.initState();
    // This keeps running even when DetailScreen is on top!
    _subscription = dataStream.listen((_) => setState(() {}));
  }

  @override
  void dispose() {
    _subscription?.cancel(); // Properly cleaned up when actually popped
    super.dispose();
  }
}

Key Rule:

textCopy

dispose()

is called when a widget is permanently removed from the tree (popped off navigation stack, or conditionally unmounted). Pushing a new route on top merely deactivates the previous screen — it remains alive in memory.