How can i show message before that the user close the app in Flutter?

You can use the WillPopScope widget to display a confirmation message before the app exits. This widget triggers whenever the user attempts to navigate away from the current screen, which can include closing the app.

Here’s an example:

Widget build(BuildContext context) {
  return WillPopScope(
    onWillPop: () async {
      final shouldExit = await showDialog(
        context: context,
        builder: (context) => AlertDialog(
          title: Text('Are you sure you want to exit?'),
          content: Text('Any unsaved changes will be lost.'),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context, false),
              child: Text('Cancel'),
            ),
            TextButton(
              onPressed: () => Navigator.pop(context, true),
              child: Text('Exit'),
            ),
          ],
        ),
      );
      return shouldExit ?? false;
    },
    child: MyHomePage(), // Your app's main content
  );
}