java - How to transfer the Firebase reference to another android activity

Question

We have 2 Android activities (activity A and activity B)

Suppose that we instantiated a Firebase reference in activity A. Activity A also handles all user authentication (Facebook, Google, and email/password).

Activity B, which is started from activity A using an Android intent, should use the Firebase reference to access some data on the Firebase servers.

Now I was wondering what the best design is to send the Firebase ref from activity A to activity B.

1. Bundle the Firebase reference with the intent using Java Serializable and use intent.getExtra() in Activity B

2. Bundle the Firebase reference with the intent using Android Parcelable and use intent.getExtra() in activity B

3. Initiate the Firebase reference in a Android service and bind each activity to that service

4. Something else.

Answer 1

The common way to do this is to pass the URL for the data to the new activity. See for example this method from the Firebase Android Drawing sample:

private void openBoard(String key) {
    Log.i(TAG, "Opening board "+key);
    Toast.makeText(BoardListActivity.this, "Opening board: "+key, Toast.LENGTH_LONG).show();
    Intent intent = new Intent(this, DrawingActivity.class);
    intent.putExtra("FIREBASE_URL", FIREBASE_URL);
    intent.putExtra("BOARD_ID", key);
    startActivity(intent);
}

The new activity then reads the URL and constructs a new Firebase reference:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent = getIntent();
    final String url = intent.getStringExtra("FIREBASE_URL");
    final String boardId = intent.getStringExtra("BOARD_ID");
    Log.i(TAG, "Adding DrawingView on "+url+" for boardId "+boardId);
    mFirebaseRef = new Firebase(url);

The authentication state is indeed maintained between these calls. The Firebase SDK maintains a single connection to the server for an application session and each Firebase reference is a lightweight reference on top of that.