title: Purpose of Container in Fragments for Android
body: <p>I am learning fragments but I am failing to understand the significance behind why fragments requires a Container.</p>
  
  <p>The way I understand Fragments work is as follows :</p>
  
  <ol>
  <li><p>FragmentActivity setContentview refers to a xml file which
  defines where fragments would be located.</p></li>
  <li><p>FragmentActivity creates instance of the fragments </p></li>
  <li><p>Then assigns fragment to container. </p></li>
  <li><p>FragmentManager then displays them. </p></li>
  <li><p>The actual Fragment class then inflates a layout, and it is this layout which
  contains all of the applications UI components.</p></li>
  </ol>
  
  <p>(please correct me if I miss something here because I am only learning at the moment).</p>
  
  <p>So why is the purpose of the Container why do we even need since in all the examples I have seen it is just a blank relative layout xml document.</p>
  
  <p>Can different fragments share the same Container (since its just a RelativeLayout xml file)?  </p>
  
  <p>So in the example provided by google <a href="http://developer.android.com/training/basics/fragments/creating.html">http://developer.android.com/training/basics/fragments/creating.html</a></p>
  
  <p>They have a ListFragment and when item is selected through the use of the CallBack interface we eventually get back to this line of code :</p>
  
  <pre><code>// Replace whatever is in the fragment_container view with this fragment,
  // and add the transaction to the back stack so the user can navigate back
  transaction.replace(R.id.fragment_container, newFragment);
  </code></pre>
  
  <p>My other question is:</p>
  
  <p>1) Why does this line of code not replace the ListFragment (left side Fragment) with the article fragment. Since when it was initialised we see:</p>
  
  <pre><code>getSupportFragmentManager().beginTransaction()
                      .add(R.id.fragment_container, firstFragment).commit();
  </code></pre>
  
  <p>Instead ... the ListFragment remains on the left and the right Fragment is updated.
  But the container fragment_container belongs to firstFragment this is the ListFragment.
  And this is not the one that gets updated.</p>
  
  <p>Do you see why I have the question ? This is not explained in the tutorial.</p>