android - NavigationDrawer 不显示 View

Question

我有一个带导航 View 的抽屉导航，有四个选项卡，其中一个是一个 fragment ，其中包括 ViewPager，即是其他 fragment 的宿主。一切正常，但是当使用 ViewPager 从 fragment 切换时，NavigationDrawer 的任何其他 fragment 都不会显示任何内容。查了日志，onCreate，onCreateView这几个 fragment 都调用了，但是为什么不显示...谁知道为什么？

抽屉导航

public class NavigationDrawerHost extends AppCompatActivity implements
        NavigationView.OnNavigationItemSelectedListener {
//буду использовать эту активность как хост под все фрагменты, чтобы верно работал мой drawer!

    public static String WHERE_FROM = NavigationDrawerHost.class.getSimpleName();

    public static Toolbar toolbar;
    public static ProgressBar progressBar;
    private DrawerLayout drawer;
    private NavigationView navigationView;
    private ActionBarDrawerToggle drawerToggle;
    private int navItemId;
    private static final String NAV_ITEM_ID = "NAV_ITEM_ID";

    private TextView userFirstNameTextView, userLastNameTextView;
    private ImageView userPhotoImageView;

    private VKAccessToken access_token; //токен это информация о правах доступа
    private VKApiUser user; //текущий пользователь

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.navigation_drawer_host);

        progressBar = (ProgressBar) findViewById(R.id.progressBar);

        drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        // Find the toolbar view inside the activity layout
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        // Set a Toolbar to replace the ActionBar.
        setSupportActionBar(toolbar);

        //setTitle(R.string.drawer_menu_posts);

        // load saved navigation state if present
        if (null == savedInstanceState) {
            navItemId = R.id.posts_fragment;
        } else {
            navItemId = savedInstanceState.getInt(NAV_ITEM_ID);
        }

        // Find our drawer view
        navigationView = (NavigationView) findViewById(R.id.nvView);
        navigationView.setNavigationItemSelectedListener(this);

        // select the correct nav menu item
        navigationView.getMenu().findItem(navItemId).setChecked(true);

        // если хотим добавить какие-то элементы в наш header,
        // то нужно добавить их в layout, а затем инициализировать нижеприведенным способом
        // Inflate the header view at runtime
        View headerLayout = navigationView.inflateHeaderView(R.layout.nav_header);
        // We can now look up items within the header if needed
        userFirstNameTextView = (TextView) headerLayout.findViewById(R.id.user_first_name);
        userLastNameTextView = (TextView) headerLayout.findViewById(R.id.user_last_name);
        userPhotoImageView = (ImageView) headerLayout.findViewById(R.id.user_photo);

        drawerToggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.drawer_open, R.string.drawer_close);

        // Tie DrawerLayout events to the ActionBarToggle
        drawer.setDrawerListener(drawerToggle);
        drawerToggle.syncState();

        selectItem(navItemId);
    }

    @Override
    protected void onSaveInstanceState(final Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt(NAV_ITEM_ID, navItemId);
    }

    // Menu icons are inflated just as they were with actionbar
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.menu_exit:
                //quitDialog();
                VKSdk.logout();
                finish();
                return true;

            default:
                return drawerToggle.onOptionsItemSelected(item) || super.onOptionsItemSelected(item);
        }
    }

    // Make sure this is the method with just `Bundle` as the signature
    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        drawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggles
        drawerToggle.onConfigurationChanged(newConfig);
    }

    private void selectItem(final int itemId) {
        // perform the actual navigation logic, updating the main content fragment etc
        // Create a new fragment and specify the planet to show based on position
        Fragment fragment = null;
        Class fragmentClass = null;

        switch (itemId) {
            case R.id.posts_fragment:
                fragmentClass = PostsFragment.class;
                fragment = new PostsFragment();
                break;
            case R.id.albums_fragment:
                fragmentClass = FragmentTest.class;
                fragment = new FragmentTest();
                break;
            case R.id.friends_fragment:
                fragmentClass = FragmentTest.class;
                fragment = new FragmentTest();
                break;
            case R.id.likes_fragment:
                fragmentClass = LikesFragment.class;
                fragment = new LikesFragment();
                break;
            /*default:
                fragmentClass = PostsFragment.class;*/
        }

        /*try {
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }*/

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.replace(R.id.fragment_container, fragment);
        transaction.addToBackStack(null);
        transaction.commit();

        drawer.closeDrawers();
    }

    @Override
    public boolean onNavigationItemSelected(final MenuItem item) {
        // update highlighted item in the navigation menu
        item.setChecked(true);
        setTitle(item.getTitle());
        navItemId = item.getItemId();

        // allow some time after closing the drawer before performing real navigation
        // so the user can see what is happening
        drawer.closeDrawer(GravityCompat.START);
        selectItem(item.getItemId());
        return true;
    }

    @Override
    public void onBackPressed() {
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
            quitDialog();
        } else {
            getSupportFragmentManager().popBackStack();
        }
    }

    private void quitDialog() {
        AlertDialog.Builder quitDialog = new AlertDialog.Builder(this);
        quitDialog.setTitle("Вы хотите выйти?");

        quitDialog.setPositiveButton("Да", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                //стираем БД
                Delete.tables(PostTable.class, PictureTable.class, PostTableMyLikes.class, PictureTableMyLikes.class);

                FlowManager.getDatabase(WallDatabase.DB_NAME).reset(NavigationDrawerHost.this);
                FlowManager.getDatabase(WallDatabaseMyLikes.DB_NAME).reset(NavigationDrawerHost.this);

                Intent intent = new Intent(Intent.ACTION_MAIN);
                intent.addCategory(Intent.CATEGORY_HOME);
                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(intent);
            }
        });

        quitDialog.setNegativeButton("Нет",
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                    }
                });

        quitDialog.show();
    }


}

Fragments的ViewPager宿主，需要通过ViewPager显示

//этот фрагмент является хостом для MyLikesFragment и FriendLikesFragment, так же тут содержатся табы
public class LikesFragment extends Fragment {

    public static String WHERE_FROM_FRIENDS_LIKES = LikesFragment.class.getSimpleName() + "_FRIENDSLIKES";

    private ViewPager viewPager;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.likes_fragment, container, false);

        TabLayout tabLayout = (TabLayout) v.findViewById(R.id.tab_layout);
        tabLayout.addTab(tabLayout.newTab().setText("Мои лайки"));
        tabLayout.addTab(tabLayout.newTab().setText("Лайки друзей"));
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

        viewPager = (ViewPager) v.findViewById(R.id.view_pager);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        viewPager.setAdapter(new LikesPagerAdapter(getChildFragmentManager()));

        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 v;
    }

    public static class LikesPagerAdapter extends FragmentPagerAdapter {
        public LikesPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public int getCount() {
            return 2;
        }

        //сделано так, чтобы передавать те аргументы, от которых будет зависеть функционал фрагмента
        @Override
        public Fragment getItem(int position) {
            return (position == 0) ? new MyLikesPostsFragment() : new PostsFragment();
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return (position == 0) ? "Мои лайки" : "Лайки друзей";
        }

    }

}

附言并且在转到同一个 fragment ViewPager 后选择抽屉中的几个项目，这不应该是

Answer 1

问题是我在主线程中调用了 adapter.notifyDataSetChanged() 并在 AsyncTask 中调用了 onPostExecute()。我的粗心......