How to load the first fragment in the Activity when the application starts?

When you start the application, an empty Activity is launched, how to start the first Fragment from the side menu?

Activity code:

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener { Fragment_Go fgo; Fragment_Programs fprograms; Fragment_Settings fsettings; Fragment_Statistic fstatistic; Fragment_Uprajnenia fuprajnenia; Fragment_zameri fzameri; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); setSupportActionBar(toolbar); DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); ActionBarDrawerToggle toggle = new ActionBarDrawerToggle( this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); drawer.addDrawerListener(toggle); toggle.syncState(); NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); navigationView.setNavigationItemSelectedListener(this); fgo = new Fragment_Go(); fprograms = new Fragment_Programs(); fsettings = new Fragment_Settings(); fstatistic = new Fragment_Statistic(); fuprajnenia = new Fragment_Uprajnenia(); fzameri = new Fragment_zameri(); } @Override public void onBackPressed() { DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); if (drawer.isDrawerOpen(GravityCompat.START)) { drawer.closeDrawer(GravityCompat.START); } else { super.onBackPressed(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); //noinspection SimplifiableIfStatement if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } @SuppressWarnings("StatementWithEmptyBody") @Override public boolean onNavigationItemSelected(MenuItem item) { // Handle navigation view item clicks here. int id = item.getItemId(); FragmentTransaction ftrans = getFragmentManager().beginTransaction(); if (id == R.id.nav_go) { ftrans.replace(R.id.container, fgo); } else if (id == R.id.nav_programs) { ftrans.replace(R.id.container, fprograms); }else if (id == R.id.nav_uprajnenia) { ftrans.replace(R.id.container, fuprajnenia); }else if (id == R.id.nav_statistic) { ftrans.replace(R.id.container, fstatistic); } else if (id == R.id.nav_zameri) { ftrans.replace(R.id.container, fzameri); } else if (id == R.id.nav_settings) { ftrans.replace(R.id.container, fsettings); } else if (id == R.id.nav_share) { } else if (id == R.id.nav_send) { } ftrans.commit(); DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); drawer.closeDrawer(GravityCompat.START); return true; } } 

Code Fragment_Go:

 public class Fragment_Go extends Fragment { // TODO: Rename parameter arguments, choose names that match // the fragment initialization parameters, eg ARG_ITEM_NUMBER private static final String ARG_PARAM1 = "param1"; private static final String ARG_PARAM2 = "param2"; // TODO: Rename and change types of parameters private String mParam1; private String mParam2; private OnFragmentInteractionListener mListener; public Fragment_Go() { // Required empty public constructor } /** * Use this factory method to create a new instance of * this fragment using the provided parameters. * * @param param1 Parameter 1. * @param param2 Parameter 2. * @return A new instance of fragment Fragment_Go. */ // TODO: Rename and change types and number of parameters public static Fragment_Go newInstance(String param1, String param2) { Fragment_Go fragment = new Fragment_Go(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment__go, container, false); } // TODO: Rename method, update argument and hook method into UI event public void onButtonPressed(Uri uri) { if (mListener != null) { mListener.onFragmentInteraction(uri); } } @Override public void onDetach() { super.onDetach(); mListener = null; } /** * This interface must be implemented by activities that contain this * fragment to allow an interaction in this fragment to be communicated * to the activity and potentially other fragments contained in that * activity. * <p> * See the Android Training lesson <a href= * "http://developer.android.com/training/basics/fragments/communicating.html" * >Communicating with Other Fragments</a> for more information. */ public interface OnFragmentInteractionListener { // TODO: Update argument type and name void onFragmentInteraction(Uri uri); } } 

Container markup:

 <?xml version="1.0" encoding="utf-8"?> <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:context="com.sharkitt.sportplus.MainActivity" tools:showIn="@layout/app_bar_main" android:id="@+id/container"> </FrameLayout>