firebase dataBase read issue

Question

I'm trying to get value from the last node on firebase Datasebase

I've seen a few solutions but none of them worked for me.

The code is given below:

            setData = FirebaseDatabase.getInstance().getReference().child("Questions");

            Query lastQuery = setData.orderByKey().limitToLast(1);
            lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                    if (dataSnapshot.hasChild("JSON_OBJ")) {
                        SubmitKey item = dataSnapshot.getValue(SubmitKey.class);
                        String key2 = item.getJSON_OBJ();

                    } else {
                        Snackbar.make(findViewById(R.id.QuestionLayout), "JSON_ObJ not found", Snackbar.LENGTH_LONG).show();
                    }

                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

My Constructor Class

public class SubmitKey {

    private String JSON_OBJ;

    public SubmitKey() {
    }

    public SubmitKey(String JSON_OBJ) {
        this.JSON_OBJ = JSON_OBJ;
    }

    public String getJSON_OBJ() {
        return JSON_OBJ;
    }
}

instead of getting the value it is going to the else statement and showing 'JSON_OBJ not Found'.

Any help would be appreciated.

Edit: I've made some changes in the code and now it is showing no setter/field found for 0-101 found on class submitKey D/ViewRootImpl@5b51511[Questions]: ViewPostIme pointer 0 D/ViewRootImpl@5b51511[Questions]: ViewPostIme pointer 1

And it is aslo not going inside if statement goes to else statement

Answer 1

When you execute a query against the Firebase Database, there will potentially be multiple results. So the snapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result.

Your onDataChange will need to take care of this list, by iterating over snapshot.getChildren():

lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snapshot) {
      for (DataSnapshot dataSnapshot: snapshot.getChildren()) {
        if (dataSnapshot.hasChild("JSON_OBJ")) {
            SubmitKey item = dataSnapshot.getValue(SubmitKey.class);
            String key2 = item.getJSON_OBJ();

        } else {
            Snackbar.make(findViewById(R.id.QuestionLayout), "JSON_ObJ not found", Snackbar.LENGTH_LONG).show();
        }
      }
    }