Android tab fragment not calling OnCreateView switching from tab2 to tab1

Question

This is the autogenerated code from android studio when selecting a 3 tabbed layout. The problem is when it starts at the first tab, it will call onCreateView in class PlaceholderFragment. When i switch to the 2nd tab, it calls it again for that tab. Now the problem starts with going back to tab1, it doesn't call onCreateView. Now if i go to tab3 it gets called for that tab, then go back to tab1 it now gets called. So tab1's onCreateView never gets called if i go from tab2 to tab1 but gets called going from tab3 to tab1. I can't figure out why it doesn't destroy this view in that specific sequence only.

I haven't modified this auto-generated code so i'd think it would have worked correctly.

public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {

SectionsPagerAdapter mSectionsPagerAdapter;

ViewPager mViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
            actionBar.setSelectedNavigationItem(position);
        }
    });

    for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {

        actionBar.addTab(
                actionBar.newTab()
                        .setText(mSectionsPagerAdapter.getPageTitle(i))
                        .setTabListener(this));
    }
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        return PlaceholderFragment.newInstance(position + 1);
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        Locale l = Locale.getDefault();
        switch (position) {
            case 0:
                return getString(R.string.title_section1).toUpperCase(l);
            case 1:
                return getString(R.string.title_section2).toUpperCase(l);
            case 2:
                return getString(R.string.title_section3).toUpperCase(l);
        }
        return null;
    }
}

public static class PlaceholderFragment extends Fragment {

    private static final String ARG_SECTION_NUMBER = "section_number";


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

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }
}

}

Answer 1

Viewpager has one public method named setOffScreenPageLimit() which indicates the number of pages that will be retained to either side of the current page in the view hierarchy in an idle state.

When you use the default implementation of setOffscreenPageLimit() it is only loading the one fragment which is to the right of it.

For example, if you are currently on index1, it has index 2 loaded in memory but not index 0, so swiping to left will load a new fragment from scratch. Use setOffScreenLimit(1), setOffScreenLimit(2) etc. it will help clear out your doubts about the concept.