Проверка данных из Firebase

Пытаюсь проверить заголовок передаваемый из Firebase. Выдает ошибку, видимо данные еще не успевают подгрузиться. Как это исправить? 66 строчка это if (str1.equals(str2))

TaskAdapter

public class TaskAdapter extends RecyclerView.Adapter<TaskAdapter.TaskViewHolder> {
    // Объявление переменных
    private FirebaseAuth mAuth;
    private FirebaseUser user;
    private DatabaseReference myRef;
    private Context mCtx;
    private List<Task> taskList;
    private String photo, author, direction, phone, kolvoMan, kolvoHour, time, date;

    public TaskAdapter(Context mCtx, List<Task> taskList) {
        this.mCtx = mCtx;
        this.taskList = taskList;
    }

    @Override
    public TaskViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        // Инициализация Firebase
        mAuth = FirebaseAuth.getInstance();
        user = mAuth.getCurrentUser();
        myRef = FirebaseDatabase.getInstance().getReference();
        return new TaskViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.task, parent, false));
    }

    @Override
    public void onBindViewHolder(final TaskViewHolder holder, final int position) {
        final Task task = taskList.get(position);

        myRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String str1 = task.title;
                String str2 = "bill";
                if (str1.equals(str2))
                    Toast.makeText(mCtx, "ok", Toast.LENGTH_LONG).show();
                // Показ
                holder.tvTitle.setText(task.title);
                holder.tvPlace.setText(task.place);
                holder.tvDesc.setText(task.desc);
                holder.tvPhone.setText(task.phone);
                holder.tvKolvoMan.setText(task.kolvoMan);
                holder.tvKolvoHour.setText(task.kolvoHour);
                holder.tvTime.setText(task.time);
                holder.tvDate.setText(task.date);
                // Обрабатываем нажатия
                holder.tvPlace.setOnClickListener (new View.OnClickListener() {
                    @Override
                    public void onClick(View v) { dataTransferPlace(position); }
                });
                holder.itemView.setOnCreateContextMenuListener(new View.OnCreateContextMenuListener() {
                    @Override
                    public void onCreateContextMenu(ContextMenu contextMenu, View view, ContextMenu.ContextMenuInfo contextMenuInfo) {
                        contextMenu.add(holder.getAdapterPosition(),0,0,"Удалить");
                    }
                });
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
                //
            }
        });
    }
    // Посылаем ключ нажатого события в активити с полным описанием события
    private void dataTransferPlace(int position) {
        final Task task = taskList.get(position);
        Intent intent = new Intent(mCtx, MapsActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.putExtra("key", task.place);
        mCtx.startActivity(intent);
    }
    @Override
    public int getItemCount() {
        return taskList.size();
    }

    // Определение элементов
    class TaskViewHolder extends RecyclerView.ViewHolder {
        TextView tvTitle, tvPlace, tvDesc, tvPhone, tvTime, tvDate, tvKolvoMan, tvKolvoHour;
        public TaskViewHolder(View itemView) {
            super(itemView);
            tvTitle = itemView.findViewById(R.id.tvTitle);
            tvPlace = itemView.findViewById(R.id.tvPlace);
            tvDesc = itemView.findViewById(R.id.tvDesc);
            tvPhone = itemView.findViewById(R.id.tvPhone);
            tvTime = itemView.findViewById(R.id.tvTime);
            tvDate = itemView.findViewById(R.id.tvDate);
            tvKolvoMan = itemView.findViewById(R.id.tvKolvoMan);
            tvKolvoHour = itemView.findViewById(R.id.tvKolvoHour);
        }
    }
}

Log

04-15 17:03:49.595 24928-24928/com.example.makarov.makarovlist E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.makarov.makarovlist, PID: 24928
    java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
        at com.example.makarov.makarovlist.TaskAdapter$1.onDataChange(TaskAdapter.java:66)
        at com.google.android.gms.internal.zzegf.zza(Unknown Source)
        at com.google.android.gms.internal.zzeia.zzbyc(Unknown Source)
        at com.google.android.gms.internal.zzeig.run(Unknown Source)
        at android.os.Handler.handleCallback(Handler.java:836)
        at android.os.Handler.dispatchMessage(Handler.java:103)
        at android.os.Looper.loop(Looper.java:203)
        at android.app.ActivityThread.main(ActivityThread.java:6361)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)