Firebase：datasnapshot.getValue（className）什么都不返回

Question

I am trying to get data using model class but in vain. There are so many questions have already been asked, but I think I am according to them, If I am missing something, Please let me know..

I am trying to get data something like this..

FirebaseHelper.firebaseDatabase().getReference().child("rooms").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for (DataSnapshot roomSnap : dataSnapshot.getChildren()) {
                Room room = roomSnap.getValue(Room.class);

                //no response
                Log.d("createdAt", room.createdAt);

                // returns all data in roomSnap
                Log.d("roomSnap", roomSnap.toString());

            }
        }
        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
        }
    });

But its not fetching data from database.

Database:

Room Model

public class Room implements Parcelable {

    private static final String TAG = "Room";


    public Room() {

    }

    public String objectID = "";
    public String createdAt = "";
    public String updatedAt = "";
    public String ACL = "";
    public String roomNumber = "";
    public String roomStatus = "";
    public String roomGuestFirstName = "";
    public String roomGuestLastName = "";
    public String guestArrival = "";
    public String guestDepature = "";

    protected Room(Parcel in) {
        objectID = in.readString();
        createdAt = in.readString();
        updatedAt = in.readString();
        ACL = in.readString();
        roomNumber = in.readString();
        roomStatus = in.readString();
        roomGuestFirstName = in.readString();
        roomGuestLastName = in.readString();
        guestArrival = in.readString();
        guestDepature = in.readString();
    }

    public static final Creator<Room> CREATOR = new Creator<Room>() {
        @Override
        public Room createFromParcel(Parcel in) {
            return new Room(in);
        }

        @Override
        public Room[] newArray(int size) {
            return new Room[size];
        }
    };

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(objectID);
        dest.writeString(createdAt);
        dest.writeString(updatedAt);
        dest.writeString(ACL);
        dest.writeString(roomNumber);
        dest.writeString(roomStatus);
        dest.writeString(roomGuestFirstName);
        dest.writeString(roomGuestLastName);
        dest.writeString(guestArrival);
        dest.writeString(guestDepature);
    }
}

I am using same class to creating room and that's working fine, just I am getting issue in data retrieving. Even there is no error and nothing in logcat,

Answer 1

It was my stupidity I was trying to get data from empty String. I was expecting at least Log-cat tag name, however I have solved this, just adding data to value like this...

Answer 2

I think the problem with your code is that you are not setting the retrieved data to a list or recycler view(anything that you are using to show data) and if this doesn't help try setting your addvalue event listener like mine in the below code. i hope this will help you.

 DatabaseReference ref = database.getReference().child("buddy_plans");
    ref.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            Buddy buddy = dataSnapshot.getValue(Buddy.class);
            listBuddy.add(buddy);
            buddyAdapter.notifyDataSetChanged();

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });