title: How to go back with WebView inside Fragment controlled by NavHostFragment?
body: <p>Current situation:</p>
  
  <ul>
  <li>There is only one activity called MainActivity.</li>
  <li>MainActivity maintains the NavHostFragment.</li>
  <li>There is a WebViewFragment which embeded a WebView inside.</li>
  <li>Thera are many other fragment controlled by NavHostFragment.</li>
  </ul>
  
  <p>What troubles me:</p>
  
  <p>I can forward web pages inside WebView, but when I press back to go back inside the WebView, the NavController handle's it, pop the fragment away. 
  Since the WebView is inside a fragment not an activity, which means there is not method called <code>onBackPressed()</code> to override.</p>
  
  <p>Reference:</p>
  
  <ul>
  <li>See <a href="https://github.com/googlesamples/android-architecture-components/tree/master/NavigationBasicSample" rel="nofollow noreferrer">NavigationBasicSample@github</a></li>
  <li>See <a href="https://developer.android.com/guide/navigation/navigation-getting-started" rel="nofollow noreferrer">Getting start with Navigation@android developer home</a></li>
  </ul>