我通过通知打开了应用程序，并希望在用户按下后使其保持打开状态？
I open the app through the notification and want to keep it open after the user presses back?

这似乎是WillPopScope小部件的用例。 该小部件将告诉您用户是否按下了后退按钮。 您只需要用它包裹您的脚手架。

这是一个如何使用它的示例：

class MessagingPage extends StatefulWidget {
  @override
  _MessagingPageState createState() => _MessagingPageState();
}

class _MessagingPageState extends State<MessagingPage> {

  bool hasComeFromNotification = true;

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: (){
        if(hasComeFromNotification){
          Navigator.of(context).pushReplacement(MaterialPageRoute(builder: (context){
            return HomePage();
          }));
          return Future.value(false); // do not call Navigator.pop() because I already called it
        } else {
          return Future.value(true); // call Navigator.pop()
        }
      },
      child: Scaffold(
        body: Center(
          child: Text('messaging'),
        ),
      ),
    );
  }
}