title: IllegalStateException: Fragment already added in the tabhost fragment
body: <pre><code>FATAL EXCEPTION: main
  Process: com.example.loan, PID: 24169
  java.lang.IllegalStateException: Fragment already added: FormFragment{428f10c8 #1 id=0x7f050055 form}
      at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1192)
      at android.support.v4.app.BackStackRecord.popFromBackStack(BackStackRecord.java:722)
      at android.support.v4.app.FragmentManagerImpl.popBackStackState(FragmentManager.java:1533)
      at android.support.v4.app.FragmentManagerImpl$2.run(FragmentManager.java:489)
      at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1484)
      at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:450)
      at android.os.Handler.handleCallback(Handler.java:733)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:136)
      at android.app.ActivityThread.main(ActivityThread.java:5068)
      at java.lang.reflect.Method.invokeNative(Native Method)
      at java.lang.reflect.Method.invoke(Method.java:515)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
      at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <p>So, I have an android app that build with the tabhost. There are three tabs in total, in the tab2, there is a button to make the fragment transaction in tab2 (which is calling the function in the fragment activity)</p>
  
  <pre><code>FragmentTransaction t = getSupportFragmentManager().beginTransaction();
          t.replace(R.id.realtabcontent, mFrag);
          t.addToBackStack(null);
          t.commit();
  </code></pre>
  
  <p>There is exception if I run like this:</p>
  
  <ol>
  <li>Inside the tab2, I press the button to change fragment</li>
  <li>Go to other tab (eg. tab 1 or tab 3)</li>
  <li>Press back button</li>
  <li>Throw exception</li>
  </ol>
  
  <p>How to fix that? Thanks for helping</p>