android - 在 fragment 之间切换时清空 RecyclerView

Question

我正在尝试实现 tablayout在fragment这已经是 BottomNavigationView 的一部分了，我在浏览导航栏时遇到问题，有一个 recycler view在fragment这是tablayout的一部分，现在当我通过 BottomNavigation 在 fragment 之间导航时recyclerview变为空，logcat 中没有任何内容.

主 Activity

public class MainActivity extends AppCompatActivity {

    private BottomNavigationView navigation;

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

        loadFragment(new HomeFragment());

    }

    private void initComponent() {


        navigation = findViewById(R.id.navigation);
        BottomNavigationViewHelper.disableShiftMode(navigation);


        navigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

               // ViewAnimation.fadeOutIn(fragme);

                Fragment fragment = null;

                switch (item.getItemId()) {
                    case R.id.home_main:
                        fragment = new HomeFragment();
                        break;

                    case R.id.search:
                        fragment = new SearchFragment();
                        break;

                    case R.id.notifications:
                        fragment = new NotificationsFragment();
                        break;

                    case R.id.favourite:
                        fragment = new FavouriteFragment();
                        break;
                }

                return loadFragment(fragment);
            }
        });

        findViewById(R.id.bt_menu).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });

    }



    private boolean loadFragment(Fragment fragment) {

        if (fragment != null) {

            getSupportFragmentManager()
                    .beginTransaction()
                    .replace(R.id.fragment_container, fragment)
                    .commit();

            return true;

        }
        return false;
    }

首页 fragment

public class HomeFragment extends Fragment {

    private ViewPager view_pager;
    private TabLayout tab_layout;


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_home, null);

        view_pager = view.findViewById(R.id.view_pager);

        setupViewPager(view_pager);

        tab_layout = view.findViewById(R.id.tab_layout);
        tab_layout.setupWithViewPager(view_pager);

        return view;
    }

    private void setupViewPager(ViewPager viewPager) {

        SectionsPagerAdapter adapter = new SectionsPagerAdapter(getActivity().getSupportFragmentManager());



        adapter.addFragment(new PresetsFragment(), "Presets");
/*        adapter.addFragment(new PresetsFragment(), "Tutorials");
        adapter.addFragment(new PresetsFragment(), "Categories");*/
        viewPager.setAdapter(adapter);
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        tab_layout = null;
        view_pager = null;
    }

预设 fragment

public class PresetsFragment extends Fragment {

    RecyclerView recyclerView;
    PresetsAdapter presetsAdapter;

    String[] presetList = {"s", "s", "d", "d"};


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_presets, container, false);
        recyclerView = view.findViewById(R.id.presetsRecyclerView);

        presetsAdapter = new PresetsAdapter(presetList, getActivity());
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        recyclerView.setAdapter(presetsAdapter);
        //presetsAdapter.notifyDataSetChanged();

        return view;
    }

    @Override
    public void onResume() {
        super.onResume();


    }
}

我花了很多时间弄明白了，但还是搞不定..

Answer 1

从您的 loadFragment 方法中，您正在使用 FrameLayout 并在 BottomNavigation 选择上替换 fragment ，当您这样做时，您每次都在创建一个新 fragment 如果您使用 ViewPager，它会很好地工作