How to handle savedInstanceState when using ViewPager?

Question

I'm using android.support.v4.view.ViewPager in an application.

When the user rotates the screen, the activity is destroyed and recreated. The fragments that are currently active in the ViewPager (usually the one on screen, the one to the left of it, and the one to the right of it) are all stored to the savedInstanceState.

A new activity is created, FragmentActivity.onCreate(savedInstanceState) is called with the fragment state, and those three fragments are re-created using the bundle. However, my onCreate also sets up the ViewPager and ViewPager adapter, which create their own fragments afresh, thus resulting in TWO of each of those three fragments.

How can I associate the automatically re-created fragments with my ViewPager's adapter rather than re-creating them from scratch?

Answer 1

Never mind. It appears that I was using FragmentPagerAdapter incorrectly.

The correct way to use FragmentPagerAdapter is to instantiate your new fragment in getItem(). I was instantiating all my fragments in the adapter's constructor instead, storing them in an array, and then looking them up in the array and returning the appropriate fragment in getItem().

If you instantiate your fragment from getItem(), then FragmentPagerAdapter.instantiateItem() will automatically use the recycle fragment instead of instantiating a new one.