6 Fragments hided/shown by ViewPager without being dismissed

Question

I have 6 Fragments within an activity that I created as I want to swipe from one to the other and need them to not being dismissed but onyl hide/show y the viewpager.

Is there a way to derive a viewpager class or a SectionsPagerAdapter to do that.

I already add

mViewPager.setOffscreenPageLimit(6); 

but it didn't work. When swiping from the 4th fragment to 3rd or to 5th, the app crashes.

Relevant parts of my code simpified and renamed Fragment classes to get the code readable:

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // create the fragment once for all !
    if (savedInstanceState == null) {
        fragment1 = Fragment1.newInstance(1);
        fragment2 = Fragment2.newInstance(2);
        fragment3 = Fragment3.newInstance(3);
        fragment4 = Fragment4.newInstance(4);
        fragment5 = Fragment5.newInstance(5);
        fragment6 = Fragment6.newInstance(6);
     }
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    mViewPager.setOffscreenPageLimit(6);
    });


    public static class Fragment1 extends Fragment {
    private static final String ARG_SECTION_NUMBER = "section_number";

    public Fragment1() {
    }

    public static Fragment1 newInstance(int sectionNumber) {
        Fragment1fragment = new Fragment1();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        fragment.setRetainInstance( true);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_1, container, false);
        TextView textView = (TextView) rootView.findViewById(R.id.section_label);
        // "Main Frag"
        textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }

    @Override
    public void onResume() {
        super.onResume();
        // The activity is about to become visible again, recalcule  
    }
}



   public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        //return PlaceholderFragment.newInstance(position + 1);
        switch (position)
        {
            case 0 : return fragment1;   //instead  of Fragment1.newInstance(1);
            case 1 : return fragment2;
            case 2 : return fragment3; 
            case 3 : return fragment4;
            case 4 : return fragment5;
            case 5 : return fragment6;
            default: return null;
        }
    }

    @Override
    public int getCount() {
        // Show 6 total pages.
        return 6;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return "SECTION 1";
            case 1:
                return "SECTION 2";
            case 2:
                return "SECTION 3";
            case 3:
                return "SECTION 4";
            case 4:
                return "SECTION 5";
            case 5:
                return "SECTION 6";
        }
        return null;
    }
}

Answer 1

Extend your section pager adapter by FragmentSatePagerAdaper And set mViewPager.setOffscreenPageLimit(6);