MainActivity.java

       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);

           mSwipeRefreshLayout = findViewById(R.id.swipe_refresh_layout);
 
           //Initialize RecyclerView
           mRecyclerView = findViewById(R.id.recycler_view);
           mRecyclerView.setHasFixedSize(true);

           LinearLayoutManager mManager = new LinearLayoutManager(this);
           mRecyclerView.setLayoutManager(mManager);

           //Initialize Database
           mDatabase = FirebaseDatabase.getInstance().getReference().child("posts");