onCreate() and onCreateView() invokes a lot more than required (Fragments)

Question

Can somebody explain why the onCreate() and onCreateView() are being invoked so many times which increments with each orientation change?

Here is very simple app which consists of one Activity composed of two Fragments. The second Fragment loads dynamically. If you define these two Fragments in main.xml there would not be such a behavior.

Here is main.xml:

       <fragment class="ets.saeref.Left"         android:id="@+id/left_frag"         android:layout_weight="70"         android:layout_width="match_parent"         android:layout_height="match_parent"/>       <FrameLayout android:id="@+id/right_frag"          android:layout_weight="30"         android:layout_width="match_parent"          android:layout_height="match_parent"/>  </LinearLayout> 

Here is left frag:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical" android:layout_width="match_parent"     android:layout_height="match_parent" android:background="#000000">     <Button android:text="Landscape" android:id="@+id/button1"         android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>  </LinearLayout> 

Here is right frag:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical" android:layout_width="match_parent"     android:layout_height="match_parent" android:background="#ffffff">     <Button android:text="Landscape" android:id="@+id/button1"         android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>  </LinearLayout> 

Left.class:

public class Left extends Fragment {      @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         Log.i("Left", "onCreate()");     }      @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,             Bundle savedInstanceState) {         Log.i("Left", "onCreateView()");         return inflater.inflate(R.layout.left, container, false);     } } 

Right.class:

public class Right extends Fragment {      @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         Log.i("Right", "onCreate()");     }      @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,             Bundle savedInstanceState) {         Log.i("Right", "onCreateView()");         return inflater.inflate(R.layout.right, container, false);     } } 

Main class:

public class Main extends Activity {     /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);          Fragment fg = new Right();         getFragmentManager().beginTransaction().add(R.id.right_frag, fg)             .commit();         Log.i("Main", "onCreate()");     } } 

Log after several orientation changes:

08-28 21:47:38.220: INFO/Main(1099): onCreate() 08-28 21:47:38.220: INFO/Right(1099): onCreateView() 08-28 21:47:38.220: INFO/Right(1099): onCreateView() 08-28 21:47:38.220: INFO/Right(1099): onCreateView() 08-28 21:47:38.220: INFO/Right(1099): onCreate() 08-28 21:47:38.220: INFO/Right(1099): onCreateView() 08-28 21:47:41.110: INFO/ActivityManager(142): Config changed: {1.0 0mcc0mnc en_US sw800dp w1280dp h752dp xlrg land finger -keyb/v/h -nav/h s.162} 08-28 21:47:41.140: INFO/Right(1099): onCreate() 08-28 21:47:41.140: INFO/Right(1099): onCreate() 08-28 21:47:41.140: INFO/Right(1099): onCreate() 08-28 21:47:41.140: INFO/Right(1099): onCreate() 08-28 21:47:41.170: INFO/Left(1099): onCreate() 08-28 21:47:41.170: INFO/Left(1099): onCreateView() 08-28 21:47:41.170: INFO/Main(1099): onCreate() 08-28 21:47:41.170: INFO/Right(1099): onCreateView() 08-28 21:47:41.170: INFO/Right(1099): onCreateView() 08-28 21:47:41.170: INFO/Right(1099): onCreateView() 08-28 21:47:41.170: INFO/Right(1099): onCreateView() 08-28 21:47:41.190: INFO/Right(1099): onCreate() 08-28 21:47:41.190: INFO/Right(1099): onCreateView() 08-28 21:47:45.070: INFO/ActivityManager(142): Config changed: {1.0 0mcc0mnc en_US sw800dp w800dp h1232dp xlrg port finger -keyb/v/h -nav/h s.163} 08-28 21:47:45.120: INFO/Right(1099): onCreate() 08-28 21:47:45.120: INFO/Right(1099): onCreate() 08-28 21:47:45.120: INFO/Right(1099): onCreate() 08-28 21:47:45.120: INFO/Right(1099): onCreate() 08-28 21:47:45.120: INFO/Right(1099): onCreate() 08-28 21:47:45.130: INFO/Left(1099): onCreate() 08-28 21:47:45.130: INFO/Left(1099): onCreateView() 08-28 21:47:45.130: INFO/Main(1099): onCreate() 08-28 21:47:45.130: INFO/Right(1099): onCreateView() 08-28 21:47:45.130: INFO/Right(1099): onCreateView() 08-28 21:47:45.130: INFO/Right(1099): onCreateView() 08-28 21:47:45.140: INFO/Right(1099): onCreateView() 08-28 21:47:45.140: INFO/Right(1099): onCreateView() 08-28 21:47:45.140: INFO/Right(1099): onCreate() 08-28 21:47:45.140: INFO/Right(1099): onCreateView() 

Answer 1

I can't point to the documentation which explains this, but the solution is to only create and add the fragment when the activity first loads, like this:

@Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);      if (savedInstanceState == null) {         Fragment fg = new Right();         getFragmentManager().beginTransaction().add(R.id.right_frag, fg)             .commit();     }     Log.i("Main", "onCreate()"); }