how to maintain backstack of fragment using FragmentStatePagerAdapter

Question

MainActivity containing Navigation drawer. Clicking on navigation drawer item,opening a fragment with viewpager. Clicking on tabs fragment item, another fragment is coming but when pressing back button the viewpager fragment coming blank. How to maintain backstack?

ViewPagerAdapter

public class ViewPagerAdapterProfile extends FragmentStatePagerAdapter{

int mNumOfTabs;

public ViewPagerAdapterProfile(FragmentManager fm, int NumOfTabs) {
    super(fm);
    this.mNumOfTabs = NumOfTabs;
}

@Override
public Fragment getItem(int position) {
    if (position ==0) {
        return new PersonalDetailsFragment();
    } else if (position == 1)
    {
        return new ProfessionalDetailsFragment();

    } else return new EmploymentDetailsFragment();
}

@Override
public int getCount() {
    return mNumOfTabs;
}

@Override
public int getItemPosition(@NonNull Object object)
{
    return PagerAdapter.POSITION_NONE;
}
}

MainActivity

public class MainActivity extends AppCompatActivity {

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

private void setListViewHeight(ExpandableListView listView, int group) {

        if ((listAdapter.getChildrenCount(i) == 0) && (i == group)) {              
            Fragment fragment = null;
            switch (group) {
                case 0:
                    fragment = new DashboardFragment();
                    tv_name.clearComposingText();
                    tv_name.setText("Dashboard");
                    break;
                case 1:
                    fragment = new MyProfileFrament();
                    tv_name.clearComposingText();
                    tv_name.setText("My Profile");
                    break;                  

                default:
                    break;
            }

            //replacing the fragment
            if (fragment != null) {
                FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
                ft.replace(R.id.content_frame, fragment);
                ft.commit();
                mDrawerLayout.closeDrawer(Gravity.LEFT);
            }

        }

    }

    ViewGroup.LayoutParams params = listView.getLayoutParams();
    int height = totalHeight
            + (listView.getDividerHeight() * (listAdapter.getGroupCount() - 1));
    params.height = height;
    listView.setLayoutParams(params);
    listView.requestLayout();
}

@Override
public void onBackPressed() {
    FragmentManager fm = getSupportFragmentManager();
    for (Fragment frag : fm.getFragments()) {
        if (frag.isVisible()) {
            FragmentManager childFm = frag.getChildFragmentManager();
            if (childFm.getBackStackEntryCount() > 0) {
                childFm.popBackStack();
                return;
            }
        }
    }
    super.onBackPressed();
}
}

MyProfileFrament

public class MyProfileFrament extends Fragment{

private ViewPager viewPager;
private TabLayout tabLayout;
private String[] pageTitle = {"Personal Details", "Education/Professional Details", "Employement Details"};

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
{
    View view = inflater.inflate(R.layout.fragment_myprofile, container, false);
    viewPager = (ViewPager) view.findViewById(R.id.view_pager);
    tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);

    for (int i = 0; i < 3; i++) {
        tabLayout.addTab(tabLayout.newTab().setText(pageTitle[i]));
    }

    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

    ViewPagerAdapterProfile pagerAdapter = new ViewPagerAdapterProfile(requireFragmentManager(), pageTitle.length);
    viewPager.setAdapter(pagerAdapter);
    //change Tab selection when swipe ViewPager
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    //change Tab selection when swipe ViewPager
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    //change ViewPager page when tab selected
    tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());
        }
        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }
        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });
    return view;
}

}

score 0 · Answer 1 · answered Jul 17 '18 at 08:44

you can maintain the backstack of fragment using :

Fragment fragment=new YourFragmentClass();
FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction ft=fragmentManager.beginTransaction();
ft.add(R.id.content_frame, fragment);
ft.hide(SourceFragment.this);
ft.addToBackStack(SourceFragment.class.getName());
ft.commit();

how to maintain backstack of fragment using FragmentStatePagerAdapter

1 Answers1