在另一个选项卡上滑动时包含 recyclerview 丢失信息的 TabLayout

Question

I have a RecyclerView in a TabLayout, works good.. I full of data the RecyclerView and works good, but when a swipe to other Tab and return and the previous Tab the data in the recyclerView disappears.. What I did wrong?

ScheduleAndGuestList.java

public class ScheduleAndGuestList extends AppCompatActivity {

    private TabLayout tabLayout;

    private ViewPager viewPager;

    private TabItem tabSchedale,tabGuests;

    private pageAdapter pagerAdapter;

    private Button btn;

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

        tabLayout =(TabLayout)findViewById(R.id.tableLayout);

        tabSchedale=(TabItem)findViewById(R.id.tabSchedulePest);
        tabGuests=(TabItem)findViewById(R.id.tabGuestsPest);

        viewPager=findViewById(R.id.viewPager);
        pagerAdapter=new pageAdapter(getSupportFragmentManager(), tabLayout.getTabCount());

        viewPager.setAdapter(pagerAdapter);



        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {

                if (tab.getPosition() == 0) {
                    pagerAdapter.notifyDataSetChanged();

                } else if (tab.getPosition() == 1) {
                    pagerAdapter.notifyDataSetChanged();

                }

            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

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

            }
        });

        viewPager.setOffscreenPageLimit(tabLayout.getTabCount());

        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));

    }
}

tabSchedule.java

public class tabSchedule extends Fragment {

    private String horaMin,stringDescrp;

    private Button btn, seleccHora;

    private EditText descrpEt;

    private ImageView img1,img2;

    private HorizontalScrollView scrollView;

    private ArrayList<String> arrayHora,arrayDescrp;

    private RecyclerView recyclerViewtab;

    listScheduleAdapter adapter=new listScheduleAdapter(arrayHora,arrayDescrp);

    public tabSchedule() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_tab_schedule, container, false);


        btn = (Button) view.findViewById(R.id.button);

        recyclerViewtab=(RecyclerView)view.findViewById(R.id.recyclerViewScheduleId);

        arrayHora=new ArrayList<String>();
        arrayDescrp=new ArrayList<String>();

        //RecyclerView
        recyclerViewtab.setLayoutManager(new LinearLayoutManager(getActivity(),LinearLayoutManager.VERTICAL,false));
        recyclerViewtab.addItemDecoration(new DividerItemDecoration(getActivity(),DividerItemDecoration.VERTICAL));
        adapter=new listScheduleAdapter(arrayHora,arrayDescrp);
        recyclerViewtab.setAdapter(adapter);


        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
                final View view = LayoutInflater.from(getActivity()).inflate(R.layout.alertdialog_addschedule, null);

                scrollView=(HorizontalScrollView)view.findViewById(R.id.scrollView);

                img1=(ImageView)view.findViewById(R.id.img1);
                img2=(ImageView)view.findViewById(R.id.img2);

                //Selecionar hora
                {
                    seleccHora = (Button) view.findViewById(R.id.seleccionarHoraSheduleId);

                    seleccHora.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            Calendar mcurrentTime = Calendar.getInstance();
                            int hour = mcurrentTime.get(Calendar.HOUR_OF_DAY);
                            int minute = mcurrentTime.get(Calendar.MINUTE);
                            TimePickerDialog mTimePicker;
                            mTimePicker = new TimePickerDialog(getActivity(), new TimePickerDialog.OnTimeSetListener() {
                                @Override
                                public void onTimeSet(TimePicker timePicker, int selectedHour, int selectedMinute) {
                                    horaMin = String.format("%02d:%02d", selectedHour, selectedMinute);

                                    seleccHora.setText(horaMin);
                                }
                            }, hour, minute, true);
                            mTimePicker.setTitle("Select Time");
                            mTimePicker.show();
                        }
                    });
                }

                img1.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        img1.setBackgroundColor(Color.parseColor("#FF4081"));
                        Toast.makeText(getActivity(), "Works 1!", Toast.LENGTH_SHORT).show();
                    }
                });

                builder.setTitle("Agregar programacion");
                builder.setPositiveButton("Agregar", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                        descrpEt=(EditText)view.findViewById(R.id.descripScheduleId);
                        stringDescrp=descrpEt.getText().toString();

                        arrayHora.add(horaMin);
                        arrayDescrp.add(stringDescrp);

                        adapter.notifyDataSetChanged();

                    }
                }).setNegativeButton("Cancelar", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                    }
                });

                builder.setView(view);
                builder.show();

            }
        });

        return view;
    }

}

pageAdapter.java

public class pageAdapter extends FragmentPagerAdapter {

    private int numOfTabs;

    public pageAdapter(@NonNull FragmentManager fm, int numOfTabs) {
        super(fm);
        this.numOfTabs = numOfTabs;
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 0:
                return new tabSchedule();
            case 1:
                return new tabGuests();
            default:
                return null;
        }
    }

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

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

Answer 1

Please, try following source code on MainActivity.java

//create viewpageradaper class object
    ViewPagerAdapter adapter=new ViewPagerAdapter(getSupportFragmentManager());
    //adding fragments using adapter object
    adapter.AddFragment(new FirstFragment(), "Home");
    adapter.AddFragment(new SecondFragment(), "Friends");
    adapter.AddFragment(new ThirdFragment(), "Group");

    //set adapter into viewpager
    viewPager.setAdapter(adapter);

    //set viewpager into tablayout
    tabLayout.setupWithViewPager(viewPager);


    //set icon to tab items
    tabLayout.getTabAt(0).setIcon(ICONS[0]);
    tabLayout.getTabAt(1).setIcon(ICONS[1]);
    tabLayout.getTabAt(2).setIcon(ICONS[2]);

ViewPagerAdapter below:

public class ViewPagerAdapter extends FragmentPagerAdapter {

private final List<Fragment> fragmentList=new ArrayList<>();
private final List<String> fragmentListTitles=new ArrayList<>();


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

@Override
public Fragment getItem(int position) {
    return fragmentList.get(position);
}

@Override
public int getCount() {
    return fragmentListTitles.size();
}


//return page title
@Override
public CharSequence getPageTitle(int position) {
    return fragmentListTitles.get(position);
}

public void AddFragment(Fragment fragment,String title)
{
    fragmentList.add(fragment);
    fragmentListTitles.add(title);
}

}