title: Navigation Architecture Component - Activities
body: <p>I've been following the docs from <a href="https://developer.android.com/topic/libraries/architecture/navigation/navigation-implementing" rel="noreferrer">Navigation Architecture Component</a> to understand how this new navigation system works. </p>
  
  <p>To go/back from one screen to another you need a component which implements <code>NavHost</code> interface.</p>
  
  <blockquote>
    <p>The NavHost is an empty view whereupon destinations are swapped in and
    out as a user navigates through your app.</p>
  </blockquote>
  
  <p>But, it seems that currently only Fragments implement <code>NavHost</code> </p>
  
  <blockquote>
    <p>The Navigation Architecture Component’s default NavHost implementation is NavHostFragment.</p>
  </blockquote>
  
  <p>So, my questions are:</p>
  
  <ul>
  <li><p>Even if I have a very simple screen which can be implemented with an <code>Activity</code>, in order to work with this new navigation system, a <code>Fragment</code> needs to be hosted containing the actual view?</p></li>
  <li><p>Will <code>Activity</code> implement <code>NavHost</code> interface in a near future?</p></li>
  </ul>
  
  <p><strong>--UPDATED--</strong> </p>
  
  <p>Based on ianhanniballake's answer, I understand that every activity contains its own navigation graph. But if I want to go from one activity to another using the nav component (replacing "old" <code>startActivity</code> call), I can use <code>activity destinations</code>. What is <code>activity destinations</code> is not clear to me because the <a href="https://developer.android.com/topic/libraries/architecture/navigation/navigation-migrate" rel="noreferrer">docs for migration</a> don't go into any detail:</p>
  
  <blockquote>
    <p>Separate Activities can then be linked by adding activity destinations to the navigation graph, replacing existing usages of startActivity() throughout the code base.</p>
  </blockquote>
  
  <ul>
  <li>Is there any benefit on using <code>ActivityNavigator</code> instead of <code>startActivity</code>? </li>
  <li>What is the proper way to go from activities when using the nav component?  </li>
  </ul>