How to store a users UID in a firebase database and have it map to a POJO

Question

CONTEXT

I am currently working on a Firebase application (in Android). I have set up authentication, storage and the database with no issues to speak of. As the Firebase

Answer 1

I used two approaches to solve this. One is to have that extra field, thus having the redundancy, and the another is to use a HashMap to map the User's POJO with it's UID.

If you have noticed that whenever you load the data from the Firebase Database, mostly it's in the form of a Map, so all I did was to save the key to a Map, which uses that key to map the User's POJO. That map was stored in a singleton so it could be accessed from anywhere in the app.

Something like this -

DatabaseReference mFirebaseRef = FirebaseDatabase.getInstance().getReference("users"); //Add your filter as your requirements. I am currently loading all the users.
mFirebaseRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Map<String, Map> map = (Map<String, Map>) dataSnapshot.getValue();
        if (map != null) {
        for (String uid : map.keySet()) {//keys will be uid
            Map<String, Map> userMap = map.get(uid); //userMap is a single user's data.
            User user = new User(userMap); //I have used a constructor to map the populate the properties of the User Model.
            getSingletonMap().push(uid,user); //pushing using the uid
        }
    }
}

This way I can get the user just by using the UID ( getSingletonMap().get(uid) )or can get the uid of a user. I hope this answers your question.

Answer 2

I had the same problem while using FirebaseRecyclerAdapter, so I copied the code and added the following method since the adapter stores the snapshots.

public String getItemKey(int position) {
    return mSnapshots.getItem(position).getKey();
}

Now you can just set the user's UID using a setter.

EDIT : I was thinking something along these lines

User.java

public class User {

    private String name;
    private String email;
    private String UID;

    public User() {
    }

    public String getUID() {
    return UID;
    }

    public void setUID(String UID) {
    this.UID = UID;
    }

    public String getEmail() {
    return email;
    }

    public void setEmail(String email) {
    this.email = email;
    }

    public String getName() {
    return name;
    }

    public void setName(String name) {
    this.name = name;
    }
}

And in your Firebase adapter's populateView()

String UID;

FirebaseListAdapter<User> searchAdapter = new FirebaseListAdapter<User>(getActivity(), User.class, R.layout.user_layout, mRef) {
        @Override
        protected void populateView(View v, User model, int position) {
            // If you really need to set the UID here              
            // model.setUID = getRef(position).getKey();
            // Otherwise, I would just set a String field as shown 
            //and pass it with the intent to get the UID 
            //in the profile Activity
            UID = getRef(position).getKey
            ((TextView) v.findViewById(R.id.text1)).setText(model.getName());
            ((TextView) v.findViewById(R.id.text2)).setText(model.getEmail());
                v.setOnClickListener(MainActivity.this);
        }
    };
    @Override
    public void onClick(View v) {
        Intent intent = new Intent(this, ProfileActivity.class);
        intent.putStringExtra(UID_EXTRA, UID);
        startActivity(intent);
    }