Retain Current Visible Fragment After Orientation Changes

Question

In my application I have 3 Fragments. suppose fragment1, fragment2, and Fragment3. these three fragments hosted on single activity. there is a Navigation drawer available to navigate each fragment. and Fragment1 is the default fragment, ie., Fragment1 is visible when the application starts. the problem is when the orientation of phone changes the current visible fragment goes out and the default fragment shows, because the activity restarts. I am keeping a the tag of current visible fragment's tag in bundle, and checks in onCreate method. but I cant create Fragment object of corresponding fragment by tag.

onCreate

if (savedInstanceState == null) {
            mFragment = new Fragment1();
            showFragment(mFragment, FRAGMENT1_TAG);
        } else {
            String tag = savedInstanceState.getString(CURRENT_FRAGMENT_TAG);
            mFragment = mFragmentManager.findFragmentByTag(tag);

            if (mFragment != null)
                mFragmentManager.beginTransaction().replace(R.id.content_frame, mFragment, tag).commit();
            else
                Toast.makeText(getBaseContext(), "Something went wrong, please restart application", Toast.LENGTH_SHORT).show();
        }

onSaveInstanceState

String fragmentTag = mFragmentManager.findFragmentById(R.id.content_frame).getTag();
        dataOut.putString(CURRENT_FRAGMENT_TAG, fragmentTag);

when the orientation changes I am getting a null pointer exception, that is the mFragment is null, how can I resolve this

UPDATE

 public static void showFragment(Fragment fragment, String tag) {
        mFragmentTag = tag;

        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.content_frame, fragment, mFragmentTag);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }

http://stackoverflow.com/questions/11182180/understanding-fragments-setretaininstanceboolean — Gordak, Jul 22 '15 at 08:34
that is about restoring fragment state, but i have to keep the activity state — droidev, Jul 22 '15 at 08:39

score 2 · Answer 1 · answered Jul 22 '15 at 08:53

2

Keep the name of the class of your Fragments in the Bundle.

Then recreate your Fragment with the name of the class, using the static method instantiate.

String name = savedInstanceState.getString(CURRENT_FRAGMENT_TAG);
Fragment fragment = Fragment.instantiate (Activity.this, "com.example." + name);

The method expects the full name (package included).

answered Jul 22 '15 at 08:53

Gordak

2,060
22
32

but in that case you will lose your backstack info , isn't there a way to kepp that also ? – Jesus Dimrix May 12 '19 at 14:36

Georgy · Accepted Answer · 2015-07-22T09:32:13.513

0

The easiest way to do it is to prevent the activity from recreating by setting android:configChanges="screenSize|orientation" in your manifest file.

UPDATE

You need to call to: super.onSaveInstanceState(outState); when overriding the onSaveInstanceState method

edited Jul 22 '15 at 09:32

answered Jul 22 '15 at 08:31

Georgy

364
2
14

actually I am making some layout changes when orientation changes. so I can't lock orientation – droidev Jul 22 '15 at 08:34
can you post the code of `showFragment` function please? – Georgy Jul 22 '15 at 08:46
Are you calling to `super.onSaveInstanceState(outState);` in your onSaveInstanceState function? – Georgy Jul 22 '15 at 09:02
That is the problem... The fragment manager doesn't save its state. Add the call to super and everything will be fine. You should always call to super when you override the life cycle methods. – Georgy Jul 22 '15 at 09:15
Not a good practice: https://developer.android.com/guide/topics/resources/runtime-changes.html#HandlingTheChange – Francis Straccia Jan 31 '17 at 09:00

Retain Current Visible Fragment After Orientation Changes

2 Answers2

UPDATE