Question

MainActivity包含导航抽屉。单击导航抽屉项，使用viewpager打开一个片段。单击选项卡上的片段项目，另一个片段即将到来，但是当按下返回按钮时，viewpager片段变成空白。如何维护后退堆栈？

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;
}

}

Answer 1

您可以使用：维护片段的后堆栈：

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();

如何使用FragmentStatePagerAdapter维护片段的堆栈

1 个答案: