Navigator Push and Pop

A stack of routes

The Navigator manages a stack of routes (full screens or dialogs). Navigator.push(context, MaterialPageRoute(builder: ...)) puts a new screen on top with a platform-appropriate transition; Navigator.pop(context, result) removes it and can return a value to the awaiting caller. pushReplacement swaps the current route (useful after sign-in), and pushAndRemoveUntil clears the stack. Dialogs and bottom sheets (showDialog, showModalBottomSheet) are routes too, so they close with pop. On Android the system back gesture pops the top route; PopScope lets a screen intercept it, for example to confirm discarding unsaved changes.

Move between screens

Flutter keeps screens on a stack of routes; a router maps URLs and deep links to that stack.

Push a screen and await a result

Returning data with pop.

Future<void> pickColour(BuildContext context) async {
  final colour = await Navigator.push<Color>(
    context,
    MaterialPageRoute(builder: (_) => const ColourPickerPage()),
  );
  if (!context.mounted) return; // the widget may be gone after the await
  if (colour != null) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Picked $colour')),
    );
  }
}

// inside ColourPickerPage
ListTile(
  title: const Text('Teal'),
  onTap: () => Navigator.pop(context, Colors.teal),
);

A stack of plates

Each new screen is a plate placed on top; pop lifts the top plate off and you are back to the one underneath, exactly as you left it.

त्वरित जाँच: How does a pushed screen return a value to the screen that opened it?

• By writing to a global variable only
• By passing it to Navigator.pop, which completes the Future returned by push
• By calling setState on the parent
• Screens cannot return values