firebase - Using Stream Building with a specific Firestore document

Question

I am building a Flutter application and I am having trouble understanding how to implement Firestore. Out of the tutorials I have seen, I only see how to create a snapshot of an entire collection, however in my case, my collection is users, so I only need to snapshot the document of a particular user. There doesn't appear to be documentation on the Firebase docs on how to do this nor is there much documentation on the FlutterFire GitHub page. Please help!

This is the Widget I'm trying to build with StreamBuilder.

  @override
  Widget build(BuildContext context) {
    return new StreamBuilder(
      stream: Firestore.instance.collection('users').document(userId).snapshots(),
      builder: (context, snapshot) {
        return new ListView.builder(
          itemCount: //what do I put here?,
          itemBuilder: (context, index) => new Item(//And here?),
        );
      }
    );
  }

Answer 1

Waitting for answers