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()

score 48 · Accepted Answer · answered Aug 29 '11 at 18:25

48

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()");
}

answered Aug 29 '11 at 18:25

Joris Wit

496
5
2

Please point to the documentation if you would found. Thanks. – Eugene Aug 30 '11 at 19:01
There are examples in the ApiDocs that do it, but as far as I know it isn't explained in the actual documentation. – Timmmm Nov 13 '12 at 15:12
4

The most formal documentation I've found on this is the following example: http://developer.android.com/training/basics/fragments/fragment-ui.html#AddAtRuntime – gardarh Jul 01 '13 at 13:24

score 13 · Answer 2 · answered Jan 17 '13 at 16:08

Yes, this is very bad documented. The explanation is that when the Activity is restored it will "auto-magically" restore the Fragments that were added in it, so adding another Fragment in your Activity will basically add another new Fragment on top of the previous Fragment\s that are actually restored by Android.

This behavior is definitely intended, and the approach suggested by @Joris Wit is the correct one.

Also this is very helpful when you think about it, because let's say you have a stack of Fragments added one on top of each other, and you can navigate back to them using the back key. In the case of a rotation, if Android would not restore the backstack of Fragments you will lose all of them, or you will have to implement some mechanism to keep track of your Fragment stack.

score 6 · Answer 3 · answered Nov 06 '11 at 17:56

6

If you don't use different layouts for different orientations, I think that you should use android:configChanges="orientation" in your manifest. http://developer.android.com/guide/topics/manifest/activity-element.html#config

answered Nov 06 '11 at 17:56

Tom Esterez

21,567
8
39
44

This is very wise! Thank you for pointing this out. As I prefer when things are said clearly: Actually you have to use `android:configChanges="orientation|screenSize"` as attribute to the related activity's `` tag in your manifest. – 1111161171159459134 Aug 23 '15 at 11:03
Yet, this practice is not recommended and `"should be avoided and used only as a last resort."` This is one of the first thing we can read when we click on your link. – 1111161171159459134 Aug 23 '15 at 11:34

franta kocourek · Answer 4 · 2013-11-25T16:37:16.747

3

Looks like you have so many fragments there! If you define fragment in xml file you can not define "it" again in your code! There are two ways how to define fragmets: dynamiclly (in your code) and statically (in your xml)! Take a look here: http://marakana.com/s/post/1250/android_fragments_tutorial

It is really good tutorial.

edited Nov 25 '13 at 16:37

answered Feb 02 '13 at 12:04

franta kocourek

1,289
13
19

score 1 · Answer 5 · edited Nov 20 '11 at 04:26

An orientation change causes the system to go through the process of saving instance state, pausing, stopping, destroying, and then creating a new instance of the activity with the saved state. So this is the reason why there is so much onCreate and onCreateView calls.

I do not think the if (savedInstanceState == null) condition in the onCreate method is a good idea; the state-saving mechanism will not work properly...

score -1 · Answer 6 · answered Apr 26 '13 at 00:31

-1

main class should extend FragmentActivity and not Activity.

also look up Activity life cycle on the android doc

answered Apr 26 '13 at 00:31

Victor Odiah

1,061
11
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onCreate() and onCreateView() invokes a lot more than required (Fragments)

6 Answers6

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