title: How to properly retain a DialogFragment through rotation?
body: <p>I have a FragmentActivity that hosts a DialogFragment.</p>
  
  <p>The DialogFragment perform network requests and handles Facebook authentication, so I need to retain it during rotation.</p>
  
  <p>I've read all the other questions relating to this issue, but none of them have actually solved the problem. </p>
  
  <p>I'm using putFragment and getFragment to save the Fragment instance and get it again during activity re-creation.</p>
  
  <p>However, I'm always getting a null pointer exception on the call to getFragment in onRestoreInstanceState. I would also like to keep the dialog from being dismissed during rotation, but so far I can't even retain the instance of it. </p>
  
  <p>Any ideas what's going wrong?</p>
  
  <p>Here's what my code currently looks like:</p>
  
  <pre><code>public class OKLoginActivity extends FragmentActivity implements OKLoginDialogListener
  {
  
      private OKLoginFragment loginDialog;
      private static final String TAG_LOGINFRAGMENT = "OKLoginFragment";
  
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
  
          FragmentManager fm = getSupportFragmentManager();
  
          if(savedInstanceState == null)
          {
              loginDialog = new OKLoginFragment(); 
              loginDialog.show(fm, TAG_LOGINFRAGMENT);
          }
      }
  
  
      @Override
      public void onSaveInstanceState(Bundle outState)
      {
          getSupportFragmentManager().putFragment(outState,TAG_LOGINFRAGMENT, loginDialog);
      }
  
      @Override
      public void onRestoreInstanceState(Bundle inState)
      {
          FragmentManager fm = getSupportFragmentManager();
          loginDialog = (OKLoginFragment) fm.getFragment(inState, TAG_LOGINFRAGMENT);
      }
  
  }
  </code></pre>
  
  <p>This is the exception stack trace:</p>
  
  <pre><code>02-01 16:31:13.684: E/AndroidRuntime(9739): FATAL EXCEPTION: main
  02-01 16:31:13.684: E/AndroidRuntime(9739): java.lang.RuntimeException: Unable to start activity ComponentInfo{io.openkit.example.sampleokapp/io.openkit.OKLoginActivity}: java.lang.NullPointerException
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3692)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread.access$700(ActivityThread.java:141)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1240)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.os.Handler.dispatchMessage(Handler.java:99)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.os.Looper.loop(Looper.java:137)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread.main(ActivityThread.java:5039)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at java.lang.reflect.Method.invokeNative(Native Method)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at java.lang.reflect.Method.invoke(Method.java:511)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at dalvik.system.NativeStart.main(Native Method)
  02-01 16:31:13.684: E/AndroidRuntime(9739): Caused by: java.lang.NullPointerException
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.support.v4.app.FragmentManagerImpl.getFragment(FragmentManager.java:528)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at io.openkit.OKLoginActivity.onRestoreInstanceState(OKLoginActivity.java:62)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.Activity.performRestoreInstanceState(Activity.java:910)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.Instrumentation.callActivityOnRestoreInstanceState(Instrumentation.java:1131)
  02-01 16:31:13.684: E/AndroidRuntime(9739):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2158)
  </code></pre>