如何在RecyclerView中显示Firebase数据库的变量“名称”和“值”

Question

Fetching Data:

    private void fetchResults() {
    mDatabaseReference.child("Users").child(id).child("Quiz").child("Results").child(id).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot resultSnapshot: dataSnapshot.getChildren()) {
                String user = resultSnapshot.getKey();
                String score = resultSnapshot.getValue(String.class);
                Results results = new Results(user, score);
                resultsList.add(results);
            }
            mAdapter.notifyDataSetChanged();

                    }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });
}

Saving Data:

 String name = RecieversName;
                HashMap<String, String> userMap = new HashMap<>();
                userMap.put(name, String.valueOf(mScore));
                mRef.child("Users").child(RecieversId).child("Quiz").child("Results").child(UID).setValue(userMap).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        if (task.isSuccessful()) {
                            Intent intent = new Intent(TakingQuiz.this, TakingQuizDone.class);
                            intent.putExtra("RecieversId",RecieversId);
                            intent.putExtra("Score", mScore.toString());
                            startActivity(intent);
                            finish();
                        }
                    }
                });

Adapter:

public class AdapterQuiz extends RecyclerView.Adapter<AdapterQuiz.ResultViewHolder>{

private FirebaseAuth mAuth;
private List<Results> mResultsList;

public AdapterQuiz(List<Results>mResultsList)

    {
    this.mResultsList = mResultsList;
    }

public class ResultViewHolder extends RecyclerView.ViewHolder{
public TextView name;
public TextView score;
public ResultViewHolder(View view)
{
    super(view);
    name = (TextView)view.findViewById(R.id.name);
    score = (TextView)view.findViewById(R.id.score);
}
}
@Override
public ResultViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
{
    View V = LayoutInflater.from(parent.getContext()).inflate(R.layout.custom_activity_results,parent,false);
    mAuth = FirebaseAuth.getInstance();
    return new ResultViewHolder(V);
}


@Override
public void onBindViewHolder(ResultViewHolder holder, int position) {

    Results results = mResultsList.get(position);

    holder.name.setText(results.getName());
    holder.score.setText(results.getScore());
}


@Override
public  int getItemCount() {
    return mResultsList.size();
}

}

Results Class

public class Results {
private String Name;
private String Score;

public Results() {
}

public Results(String Name, String Score) {
    this.Name = Name;
    this.Score = Score;
}

public String getName() {
    return Name;
}

public void setName(String name) {
    Name = name;
}

public String getScore() {
    return Score;
}

public void setScore(String score) {
    Score = score;
}

}

I have worked quite sometime on RecyclerView and Firebase but usually I would display a constant 'name' and a variable 'value' but here both name and variable is not decided by me... when the user finishes the quiz and his score will be displayed in the recyclerview but its just showing blank without any error... I'm not sure if this is the right way of fetching this kind of data... can anyone help me out please

Database - https://ibb.co/eMWkFJ

Answer 1

Results results;
String name, score;
private void fetchResults() {
    mDatabaseReference.child("Users").child(id).child("Quiz").child("Results").child(id).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
             for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
                 name = childDataSnapshot.getKey().toString();
                 score = childDataSnapshot.child(name).getValue());
                 results = new Results(user, score);
                 resultsList.add(results);
                 mAdapter.notifyDataSetChanged();
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });
}

I hope this will do your job.

Answer 2

To solve this, you first need to set the adapter before notifying it for changes. So please use the following line of code:

mRecyclerView.setAdapter(mAdapter);

Instead of this:

mAdapter.notifyDataSetChanged();

This last line of code should be used only when some changes take place in your database and in order to notify the adapter, this must be set in the fist place.