Saving Fragment state in ViewPager

Question

I tried out the sample code from the API and it didn't really work so I implemented my own:

FragmentPagerSupport

public class FragmentPagerSupport extends FragmentActivity {  static final int NUM_ITEMS = 10; MyAdapter mAdapter; ViewPager mPager;  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);      mAdapter = new MyAdapter(getSupportFragmentManager());     Log.i("Pager", "mAdapter = " + mAdapter.toString());      mPager = (ViewPager)findViewById(R.id.pager);     if (mPager == null)         Log.i("Pager", "mPager = null");     else          Log.i("Pager", "mPager = " + mPager.toString());      Log.i("Pager", "Setting Pager Adapter");     mPager.setAdapter(mAdapter); }  public static class MyAdapter extends FragmentPagerAdapter {     public MyAdapter(FragmentManager fm) {         super(fm);         Log.i("Pager", "MyAdapter constructor");     }      @Override     public int getCount() {         Log.i("Pager", "MyAdapter.getCount()");         return NUM_ITEMS;                 }      @Override     public Fragment getItem(int position) {         Log.i("Pager", "MyAdapter.getItem()");          return TestFragment.newInstance(position);     } }  public static class TestFragment extends Fragment {      public static TestFragment newInstance(int position) {         Log.i("Pager", "TestFragment.newInstance()");          TestFragment fragment = new TestFragment();          Bundle args = new Bundle();         args.putInt("position", position);         fragment.setArguments(args);          return fragment;     }     @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,             Bundle savedInstanceState) {         // TODO Auto-generated method stub         Log.i("Pager", "TestFragment.onCreateView()");          LinearLayout layout = (LinearLayout)inflater.inflate(R.layout.fragment_item, null);         int position = getArguments().getInt("position");          TextView tv = (TextView)layout.findViewById(R.id.text);         tv.setText("Fragment # " + position);         tv.setTextColor(Color.WHITE);         tv.setTextSize(30);          return layout;     }  } 

}

main.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     >     <android.support.v4.view.ViewPager     android:id="@+id/pager"     android:layout_width="match_parent"     android:layout_height="match_parent"     /> </LinearLayout> 

fragment_item.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     >     <TextView       android:id="@+id/text"     android:layout_width="match_parent"      android:layout_height="match_parent"     android:gravity="center"      android:text="@string/hello"     /> </LinearLayout> 

My question is, instead of creating a new Fragment instance each time the user swipes left and right, how do I save a fragment's state (to some data structure) and then restore it?

The API demo doesn't seem to have any state information saving code at all.

Answer 1

Use ViewPager.setOffscreenPageLimit() in FragmentActivity

ViewPager pager = (ViewPager) findViewById(R.id.viewPager); pager.setOffscreenPageLimit(2); 

See more at How do I tell my custom FragmentPagerAdapter to stop destroying my fragments?

Answer 2

just override this method in FragmentpagerAdapter

@Override         public void destroyItem(ViewGroup container, int position, Object object) {             // TODO Auto-generated method stub             super.destroyItem(ViewGroup container, int position, Object object);         } 

remove super.destroyItem(ViewGroup container, int position, Object object);

from your code