title: App closed after click on back button in Fragment
body: <p>[UPDATE]</p>
  
  <p>Problem solved : Simply add "addToBackStack(null)" before commit fragment :</p>
  
  <pre><code>Fragment fragment = new WebBrowserFragment();
  fragment.setArguments(arguments);
  FragmentTransaction fragmentTransaction = getActivity().getFragmentManager().beginTransaction();
  fragmentTransaction.replace(R.id.content_frame, fragment);
  fragmentTransaction.addToBackStack(null);
  fragmentTransaction.commit();
  </code></pre>
  
  <p>Here is the code of my fragment. When i am on this fragment and i click on back button, my application is closed.</p>
  
  <p>I would like to go back on the previous loaded fragment.</p>
  
  <p>What can i do to force this behavior ?</p>
  
  <pre><code>public class WebBrowserFragment extends Fragment {
  
      WebView mWebView;
      ProgressBar progressB = null;
      private String mUrl;
      private static String mtitle;
      private static String msource;
  
      @Override
      public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
          LayoutInflater mInflater = (LayoutInflater) getActivity().getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
          View view =  (View) mInflater.inflate(R.layout.web_browser_view, null);
  
          MainActivity.setShareButtonToVisible();
  
          Bundle bundle = getArguments(); 
          String url = bundle.getString("URL");
          mtitle = bundle.getString("TITRE");
          msource = bundle.getString("SOURCE");
  
          mUrl = url;
  
          progressB = (ProgressBar) view.findViewById(R.id.progressBar1);
  
          mWebView = (WebView) view.findViewById(R.id.webViewArticle);
          mWebView.setWebChromeClient(new WebChromeClient() {
              public void onProgressChanged(WebView view, int progress) {
                  if(progress &lt; 100 &amp;&amp; progressB.getVisibility() == ProgressBar.GONE){
                      progressB.setVisibility(ProgressBar.VISIBLE);
                  }
                  progressB.setProgress(progress);
                  if(progress == 100) {
                      progressB.setVisibility(ProgressBar.GONE);
                  }
              }
          });
          mWebView.loadUrl(url);  
          return view;
      }
  </code></pre>