Know which Route was removed in onPopPage on Navigation 2.0 in Flutter

Question

I want to know which Page was being removed by the navigation in Flutter (I'm using Navigation 2.0). I have the following code:

@override
  Widget build(BuildContext context) {
    return Navigator(
      key: this.navigatorKey,
      onPopPage: (route, result) {
        if (!route.didPop(result)) return false;

        // TODO check for the page that was poped
        viewModel.otherUserIDForChat = null;

        return true;
      },
      pages: _generatePages(),
    );
  }

As seen in the previous code I'm setting to null the otherUserIDForChat, however, I would like to know if the page that was poped was the chat screen that I've implemented inside the _generatePages, here's the code for that:

/// Function that aggregates pages depending on [AppViewModel]'s values
  List<Page> _generatePages() {
    List<Page> pages = [];

    pages.add(
      MaterialPage(
        child: HomeScreen(),
      ),
    );

    if (viewModel.otherUserIDForChat != null) {
      pages.add(
        MaterialPage(
          key: ValueKey(viewModel.otherUserIDForChat),
          child: SingleChatScreen(
            parameters: SingleChatScreenParameters(
              otherUserID: viewModel.otherUserIDForChat,
            ),
          ),
        ),
      );
    }

    return pages;
  }

How can I know which page was being poped?

Solution

You can give your page a name:

MaterialPage(
    key: ValueKey(viewModel.otherUserIDForChat),
    name: viewModel.otherUserIDForChat,
    child: SingleChatScreen( ... ),
),

then in opPopPage you can check for the name:

onPopPage: (route, result) {
   if (!route.didPop(result)) return false;

   if (route.settings.name == viewModel.otherUserIDForChat) {
       // do your thing
   }

   return true;
}

Comments

[Tanha Patel]

whatever the page is displayed will be popped out of the stack as it removes the page which is on top.

[Andrey Solera]

yes, but I have multiple pages and I want to react differently when each screen is being poped, how can I know the exact page that was poped out?

[Tanha Patel]

In that case you can take reverse approach that if you want to navigate to screen A then while navigating pop desired screen and so on. As the Navigatore.pop() simply pops out the top most screen.