pushReplacement showing back arrow flutter

Question

I have a main screen with a custom bottom navigation bar, when an icon is clicked it sets the current index to the icon that was clicked. But when index number 2 is clicked it does a full page route to another page to add a "post". After the post is submitted a pushReplacement happens back to the main screen (to prevent going back). But after it routes to the main screen to the default screen at index 0, a back button still shows at the top. It goes away after I click it, but the data on that screen is slightly different. How can I fix this?

Part of the code on my main screen:

Widget customNav() {
  return Container(
      color: Colors.white,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[

         //some icons before

          IconButton(
            icon: Icon(Icons.add_circle),
            onPressed: () => Navigator.push(
                context,
                FadeRoute(
                    builder: (_) => BlocProvider<AppBloc>(
                        builder: (_, bloc) => bloc ?? AppBloc(),
                        onDispose: (_, bloc) => bloc.dispose(),
                        child: AddPost(userBloc: widget.userBloc)))),
          ),

          //icons after

        ],
      ));
}

Add Post page:

_submitFunc() async {
 // sending it to backend
  if (everything is good) {
    Navigator.pushReplacement(
      context,
      FadeRoute(
          builder: (_) =>
              BlocProvider<AppBloc>(
                  builder: (_, bloc) => bloc ?? AppBloc(),
                  onDispose: (_, bloc) => bloc.dispose(),
                  child: MainScreen(userBloc: widget.userBloc))),
    );
  }

Answer 1

Seems like it might be a routing issue. Navigator.pushReplacement() replaces whatever you've got at that point in the route, so you're essentially setting up a route that goes:

start: MainScreen
push:  MainScreen -> AddScreen
pushReplacement: MainScreen (A) -> MainScreen (B)

This is why the back button goes away after you tap it, it takes you from MainScreen B (which has historical context to go back to) to MainScreen A (which doesn't).

You may want to use Navigator.pop() to return to the original MainScreen instead of replacing the current view with a new one, or use

Navigator.pushAndRemoveUntil(newRoute, (route)=>false);

to clear all Navigator route history if you want to send the user to a new screen without being able to go back at all.