title: Fragment not loading with bottom navigation view
body: <p>Hi i'm making app where i'm using bottom navigation to navigate through the fragments but my problem is when i click the app is loaded fragments are not visible in frame layout and even when i click bottom navigation it is just showing blank page 
  below is my code for main activity
  I searched for this problem on google but looks like i'm the only one having this problem</p>
  
  <pre><code> public class MainActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener{
         FrameLayout frameLayout;
         FragmentManager fragmentManager;
         Fragment fragment;
         BottomNavigationView bottomNavigationView;
  
  
  @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
  
          fragmentManager = getSupportFragmentManager();
  
          if(findViewById(R.id.frame_container)!=null){
              if(savedInstanceState!=null){
  
                  return;
              }
  
          }
          bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_nav);
          //bottomNavigationView.setOnNavigationItemSelectedListener(this);
          //final SeekBar sb = (SeekBar) findViewById(R.id.sb);
  
      }
  
  
      @Override
      public boolean onNavigationItemSelected(@NonNull MenuItem item) {
          Fragment fragment = null;
          switch (item.getItemId()){
              case R.id.navigation_home:
                  fragment = new HomeFragment();
                  loadFragment(fragment);
                  return true;
              case R.id.navigation_feed:
                  fragment = new FeedFragment();
                  loadFragment(fragment);
                  return true;
              case R.id.navigation_event:
                  fragment = new EventsFragment();
                  loadFragment(fragment);
                  return true;
              case R.id.navigation_nearby:
                  fragment = new NearbyFragment();
                  loadFragment(fragment);
                  return true;
              case R.id.navigation_profile:
                  fragment = new ProfileFragment();
                  loadFragment(fragment);
                  return true;
          }
  
          return false;
      }
  
  
      private void loadFragment(Fragment fragment) {
          // load fragment
          //HomeFragment homeFragment = new HomeFragment();
          FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
          transaction.replace(R.id.frame_container, fragment,null);
         // transaction.addToBackStack(null);
        /* Comment this line and it should work!*/
          //transaction.addToBackStack(null);
          transaction.commit();
      }
  
  }
  </code></pre>
  
  <p>and my xml</p>
  
  <pre><code>&lt;LinearLayout android:layout_width="match_parent"
      android:layout_height="match_parent"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      android:fillViewport="true"
      android:fitsSystemWindows="true"
      android:orientation="vertical"
      xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
  &lt;FrameLayout
      android:id="@+id/frame_container"
      android:layout_width="match_parent"
      android:layout_height="0dp"
      android:layout_weight="1"&gt;
  
  &lt;/FrameLayout&gt;
      &lt;android.support.design.widget.BottomNavigationView
          android:id="@+id/bottom_nav"
          android:layout_width="match_parent"
          android:layout_height="0dp"
          app:menu="@menu/navigation"
          android:backgroundTint="@color/nav_color"
          app:itemIconTint="@color/bottom_nav_fore_color"
          android:background="?android:attr/windowBackground"
          android:layout_weight="0.1"&gt;
  
      &lt;/android.support.design.widget.BottomNavigationView&gt;
  &lt;/LinearLayout&gt;
  </code></pre>