title: How to hide NavigationIcon on toolbar
body: <p>I have following design in my project - 
  Activity (which have menuitems A, B, C, D)
  if we click on menuItem A then a FragmentA opens.I'm adding this fragment on top of activity, So toolbar remains same. 
  FragmentA onCreateView is - </p>
  
  <pre><code>    @Override
          public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                   Bundle savedInstanceState) {
              // Inflate the layout for this fragment
              rootView =  inflater.inflate(R.layout.fragment_a, container, false)
  
              Activity.toolbar.setTitle("FragmentA");
              Activity.toolbar.setNavigationIcon(R.drawable.back_icon);
  
              Activity.toolbar.setNavigationOnClickListener(new View.OnClickListener() {
                  @Override
                  public void onClick(View view) {
                      Activity.fragmentManager.popBackStack();
                      Activity.toolbar.setTitle("Activity");
                  }
              }); 
  }
  </code></pre>
  
  <p>So Basically in FragmentA I inflate Back Navigation Icon on toolbar. but i want to hide this icon when switch back to my Activity. I don't have any navigation icon or logo in Activity.</p>