title: Caused by: java.lang.IllegalStateException: Fragment already added
body: <p>My MainActivity's <code>onStart()</code> throws <code>IllegalStateException</code> with 'Fragment Already Added' message. What am i doing wrong?</p>
  
  <pre><code>public class MainActivity extends FragmentActivity implements ServiceConnection {
  
      @Override
      protected void onStart() {
          super.onStart();
      }
  }
  </code></pre>
  
  <p>Following is exception stacktrace:</p>
  
  <pre><code>java.lang.RuntimeException: 
  Unable to start activity ComponentInfo{com.xxx/com.xxx.MainActivity}:
  java.lang.IllegalStateException: Fragment already added: cj{38f8de4c #0 id=0x7f0b0079 cj}
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3190)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3300)
      at android.app.ActivityThread.access$1000(ActivityThread.java:211)
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1705)
      at android.os.Handler.dispatchMessage(Handler.java:102)
      at android.os.Looper.loop(Looper.java:145)
      at android.app.ActivityThread.main(ActivityThread.java:6946)
      at java.lang.reflect.Method.invoke(Native Method)
      at java.lang.reflect.Method.invoke(Method.java:372)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
      Caused by: java.lang.IllegalStateException: Fragment already added: cj{38f8de4c #0 id=0x7f0b0079 cj}
      at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1366)
      at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:734)
      at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1682)
      at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
      at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:607)
      at com.xxx.MainActivity.onStart(MainActivity.java:692)
      at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1264)
      at android.app.Activity.performStart(Activity.java:6613)
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3153)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3300) 
      at android.app.ActivityThread.access$1000(ActivityThread.java:211) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1705) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:145) 
      at android.app.ActivityThread.main(ActivityThread.java:6946) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:372) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199) 
  </code></pre>