title: Android - update toolbar title in activity while handle back navigation with fragment
body: <p>I have Activity hosted slide menu with fragments , when user click at any item in slidemenu fragment is opened , I need to handle back navigation </p>
  
  <p>when user click at item in list I call this method to display proper fragment </p>
  
  <pre><code>public void SelectItem(int position) {
  
          Fragment _fragment = null;
          switch (position) {
              case 0:
                  _fragment = Test_Home.newInstance();
                  break;
  
              case 1:
                  _fragment = Diseases_Fragment.newInstance();
                  break;
  
            ........
  
              case 8:
                  Logout();
                  break;
  
              default:
                 break;
  
          }
  
          if (_fragment != null) {
              FragmentManager fragmentManager = getSupportFragmentManager();
              fragmentManager.beginTransaction().replace(R.id.view_content, _fragment).addToBackStack(null).commit();
               // set title , this textview in toolbar 
              _frag_title.setText(nav_items[position]);
              mDrawerLayout.closeDrawer(GravityCompat.START);
          }
  </code></pre>
  
  <p>this method to handle back button</p>
  
  <pre><code>@Override
      public void onBackPressed() {
          if (getFragmentManager().getBackStackEntryCount() &gt; 0) {
              getFragmentManager().popBackStack();
          } else {
              super.onBackPressed();
          }
      }
  </code></pre>
  
  <p>my onCreate method</p>
  
  <pre><code> @Override
          protected void onCreate(Bundle savedInstanceState) {
              super.onCreate(savedInstanceState);
              setContentView(R.layout.home_view);
              Toolbar _toolbar = (Toolbar) findViewById(R.id.toolbar);
  
             setSupportActionBar(_toolbar);
             getSupportActionBar().setHomeButtonEnabled(true);
             getSupportActionBar().setDisplayHomeAsUpEnabled(true);
             _frag_title = (TextView) _toolbar.findViewById(R.id.frag_title);
      }
  </code></pre>
  
  <p>in fact it work just fine , but my problem is displayed fragment show old title dont show new title </p>
  
  <p>is there way call my method <code>_frag_title.setText(nav_items[position]);</code> </p>
  
  <p>my problem not in back navigation , my problem how to update toolbar title in navigation </p>