Android Firebase DataSnapshot Cast to Class

Question

I have a firebase database. When I get value from the snapshot, I have HashMap in below:

and I have a Snap class like below. How can I cast the DataSnapshot to List of the class such as List<Snap> snapList = (HashMap<String,Object>) dataSnapshot.child(USER_PHONE).child("friends").getValue();

public class Snap {

    String key;
    String value;

    public  Snap(){

    }
    public Snap(String key, String value) {
        this.key = key;
        this.value = value;
    }

    public String getKey() {
        return key;
    }

    public String getValue() {
        return value;
    }
}

Answer 1

There is no way in Java in which you can cast a HashMap<String,Object> to a List<Snap>. What can you do instead, is to query your database and get all the Snap objects and then add them to a List<Snap>.

ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            Snap snap = ds.getValue(Snap.class);
            snapList.add(snap);
        }
    }

    @Override
    public void onCancelled(DatabaseError error) {
        Log.d("TAG", error.getMessage()); //Never ignore potential errors!
    }
};
yourRef.addListenerForSingleValueEvent(eventListener);