title: Switching Fragments in navigation drawer using onNavigationItemSelected()
body: <p>So I have gone through many answers on StackOverFlow but could not get this working. I want to switch fragments on navigation drawer item click. I am using the default navigation drawer in Android Studio 1.5.</p>
  
  <p>I followed <a href="https://stackoverflow.com/questions/32944798/switch-between-fragments-with-onnavigationitemselected-in-new-navigation-drawer">this</a> answer, i have made sure that i have all my fragments created. The problem is whenever i click on any menu item the app stops working. Here's what I have till now.</p>
  
  <p>MainActivity.java</p>
  
  <pre><code>import android.os.Bundle;
  import android.support.design.widget.FloatingActionButton;
  import android.support.design.widget.Snackbar;
  import android.support.v4.app.Fragment;
  import android.support.v4.app.FragmentTransaction;
  import android.view.View;
  import android.support.design.widget.NavigationView;
  import android.support.v4.view.GravityCompat;
  import android.support.v4.widget.DrawerLayout;
  import android.support.v7.app.ActionBarDrawerToggle;
  import android.support.v7.app.AppCompatActivity;
  import android.support.v7.widget.Toolbar;
  import android.view.Menu;
  import android.view.MenuItem;
  
  public class MainActivity extends AppCompatActivity
          implements NavigationView.OnNavigationItemSelectedListener {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
          setSupportActionBar(toolbar);
  
          FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
          fab.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View view) {
                  Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                          .setAction("Action", null).show();
              }
          });
  
          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.setDrawerListener(toggle);
          toggle.syncState();
  
          NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
          navigationView.setNavigationItemSelectedListener(this);
  
          displayView(R.id.twitter);
      }
  
      @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.
          displayView(item.getItemId());
          return true;
      }
  
      public void displayView(int viewId) {
  
          Fragment fragment = null;
          String title = getString(R.string.app_name);
  
          switch (viewId) {
              case R.id.facebook:
                  fragment = new FacebookFragment();
                  title = "Facebook";
                  break;
              case R.id.twitter:
                  fragment = new TwitterFragment();
                  title = "Twitter";
                  break;
              case R.id.googleplus:
                  fragment = new GooglePlusFragment();
                  title = "Google Plus";
                  break;
              case R.id.settings:
                  fragment = new SettingsFragment();
                  title = "Settings";
                  break;
          }
  
          if (fragment != null) {
              FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
              ft.replace(R.id.content_frame, fragment);
              ft.commit();
          }
  
          // set the toolbar title
          if (getSupportActionBar() != null) {
              getSupportActionBar().setTitle(title);
          }
  
          DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
          drawer.closeDrawer(GravityCompat.START);
  
      }
  }
  </code></pre>
  
  <p>FacebookFragment.java</p>
  
  <pre><code>import android.content.Context;
  import android.net.Uri;
  import android.os.Bundle;
  import android.support.v4.app.Fragment;
  import android.view.LayoutInflater;
  import android.view.View;
  import android.view.ViewGroup;
  
  
  /**
   * A simple {@link Fragment} subclass.
   * Activities that contain this fragment must implement the
   * {@link FacebookFragment.OnFragmentInteractionListener} interface
   * to handle interaction events.
   * Use the {@link FacebookFragment#newInstance} factory method to
   * create an instance of this fragment.
   */
  public class FacebookFragment extends Fragment {
      // TODO: Rename parameter arguments, choose names that match
      // the fragment initialization parameters, e.g. 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 FacebookFragment() {
          // 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 FacebookFragment.
       */
      // TODO: Rename and change types and number of parameters
      public static FacebookFragment newInstance(String param1, String param2) {
          FacebookFragment fragment = new FacebookFragment();
          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_facebook, 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 onAttach(Context context) {
          super.onAttach(context);
          if (context instanceof OnFragmentInteractionListener) {
              mListener = (OnFragmentInteractionListener) context;
          } else {
              throw new RuntimeException(context.toString()
                      + " must implement OnFragmentInteractionListener");
          }
      }
  
      @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.
       * &lt;p/&gt;
       * See the Android Training lesson &lt;a href=
       * "http://developer.android.com/training/basics/fragments/communicating.html"
       * &gt;Communicating with Other Fragments&lt;/a&gt; for more information.
       */
      public interface OnFragmentInteractionListener {
          // TODO: Update argument type and name
          void onFragmentInteraction(Uri uri);
      }
  }
  </code></pre>
  
  <p>I have added FrameLayout to content_main.xml file as it was suggested in the question i referred to. Any help is appreciated.</p>