firebase - How to get sub-collections of every collection in Firestore using Flutter

Question

I'm building a task management app where every user has multiple projects (collections), inside every project there are tasks (collections), and inside every task there are sub-tasks.

I was able to retrieve all the projects using this code:

User user = Provider.of<User>(context);
CollectionReference projects = Firestore.instance.collection('users').document(user.uid).collection("projects");

But my question is how can I get all the tasks and sub-tasks (if they exist) from every project and list them in a StreamBuilder?

Here's my current code:

Flexible(
            child: StreamBuilder<QuerySnapshot>(
              stream: projects.snapshots(),
              builder: (BuildContext context,
                  AsyncSnapshot<QuerySnapshot> snapshot) {
                if (snapshot.hasError) {
                  return Text('Something went wrong');
                }

                if (snapshot.connectionState == ConnectionState.waiting) {
                  return Text("Loading");
                }

                return new ListView(
                  children:
                      snapshot.data.documents.map((DocumentSnapshot document) {
                    return new ListTile(
                      title: new Text(document.data['project_name']),
                      subtitle: new Text(document.data['project_description']),
                    );
                  }).toList(),
                );
              },
            ),
          ),

If the project has tasks I want to display them below the project description, and if the task has sub-tasks I want to show them below its parent task.

Answer 1

Waitting for answers