MyHomePage.dart

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  
  Future<void> secureScreen() async {
    await FlutterWindowManager.addFlags(FlutterWindowManager.FLAG_SECURE); 
  }
  
  @override
  void initState() {

    secureScreen();

    super.initState();
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Secure App Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'This page is secured',
            ),
          ],
        ),
      ),
    );
  }

}