ViewPager 不显示页面内容/更改视图后不刷新

Question

我在我的一个应用程序片段中使用 ViewPager / FragmentPagerAdapter 在每个页面中显示不同的列表视图（见下图）：

问题是在我更改当前视图（片段）并再次重新打开它后，列表视图没有呈现（见下图）:

行为是随机的，有时当我在不同 tabs/pages 之间滑动时会显示列表视图。

这是我的片段代码：

public class AstucesFragment extends Fragment implements ActionBar.TabListener {

    ActionBar actionBar;
    AppSectionsPagerAdapter mAppSectionsPagerAdapter;

    ViewPager mViewPager;
    public static String[] tabslist = new String[5];

    public AstucesFragment() {

    }

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

        tabslist[0] = getActivity().getResources().getString(R.string.astuces_quotidien);
        tabslist[1] = getActivity().getResources().getString(R.string.astuces_resto);
        tabslist[2] = getActivity().getResources().getString(R.string.astuces_loisirs);
        tabslist[3] = getActivity().getResources().getString(R.string.astuces_transports);
        tabslist[4] = getActivity().getResources().getString(R.string.astuces_tous);

        mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getActivity().getSupportFragmentManager());

        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        mViewPager = (ViewPager) view.findViewById(R.id.astuces_pager);
        mViewPager.setAdapter(mAppSectionsPagerAdapter);
        mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }
        });

        actionBar.addTab(
                actionBar.newTab()
                        .setCustomView(R.layout.fragment_astuces_tabs_quotidien)
                        .setTabListener(this));

        actionBar.addTab(
                actionBar.newTab()
                        .setCustomView(R.layout.fragment_astuces_tabs_resto)
                        .setTabListener(this));

        actionBar.addTab(
                actionBar.newTab()
                        .setCustomView(R.layout.fragment_astuces_tabs_loisirs)
                        .setTabListener(this));

        actionBar.addTab(
                actionBar.newTab()
                        .setCustomView(R.layout.fragment_astuces_tabs_transports)
                        .setTabListener(this));

        actionBar.addTab(
                actionBar.newTab()
                        .setCustomView(R.layout.fragment_astuces_tabs_tous)
                        .setTabListener(this));

        return view;
    }



    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        mViewPager.setCurrentItem(tab.getPosition());
        Log.i("AstucesFragment","onTabSelected()");
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {

    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        mViewPager.setCurrentItem(tab.getPosition());
        Log.i("AstucesFragment","onTabReselected()");
    }


    /**
     * A {@link android.support.v4.app.FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
     * sections of the app.
     */
    public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {


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

        @Override
        public Fragment getItem(int i) {
            Log.i("AppSectionsPagerAdapter","Page ID : "+i);
            // The other sections of the app are dummy placeholders.
            Fragment fragment = new AstucesListFragment();
            Bundle args = new Bundle();
            args.putString(AstucesListFragment.ARG_PAGE_CAT, tabslist[i]);
            fragment.setArguments(args);
            return fragment;
        }

        @Override
        public int getCount() {
            return tabslist.length;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return tabslist[position];
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            super.destroyItem(container, position, object);
        }
    }

    /**
     * A dummy fragment representing a section of the app, but that simply displays dummy text.
     */
    public static class AstucesListFragment extends Fragment {

        public static final String ARG_PAGE_CAT = "page_cat";

        private List<Astuce> astuceList = new ArrayList<Astuce>();
        private ListView listView;
        private AstuceAdapter adapter;
        private AstuceDAO astuceDAO;

        public AstucesListFragment() {

        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_astuces_page, container, false);
            Bundle args = getArguments();

            Log.i("AstucesListFragment","onCreateView()");


            String theme = "";
            if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_quotidien)) theme = "Q";
            else if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_resto)) theme = "R";
            else if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_loisirs)) theme = "L";
            else if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_transports)) theme = "T";
            else theme = "";


            astuceDAO = new AstuceDAO();
            astuceList = astuceDAO.findAstuceByTheme(theme);

            listView = (ListView) rootView.findViewById(R.id.astuces_list);
            adapter = new AstuceAdapter(getActivity(), astuceList);
            listView.setAdapter(adapter);
            adapter.notifyDataSetChanged();


            return rootView;
        }
    }

}

我该如何解决这个问题？

Answer 1

如果您希望片段在更改选项卡后仍保持其状态，试试这个，

mViewPager.setOffscreenPageLimit(5); //因为你有 5 个片段

但这会使activity在调用activity时同时初始化所有片段。

另一种方法是使用 FragmentStatePagerAdapter 而不是 FragmentPagerAdapter。参考，

http://developer.android.com/reference/android/support/v4/app/FragmentStatePagerAdapter.html

Answer 2

您没有正确比较字符串。比较两个字符串时，您需要使用 equals() 方法而不是 == 运算符。所以在 onCreateView() 中 AstucesListFragment 替换

if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_quotidien)) theme = "Q";
else if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_resto)) theme = "R";
else if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_loisirs)) theme = "L";
else if (args.getString(ARG_PAGE_CAT) == getString(R.string.astuces_transports)) theme = "T";
else theme = "";

和

if (args.getString(ARG_PAGE_CAT).equals(getString(R.string.astuces_quotidien))) theme = "Q";
else if (args.getString(ARG_PAGE_CAT).equals( getString(R.string.astuces_resto))) theme = "R";
else if (args.getString(ARG_PAGE_CAT).equals( getString(R.string.astuces_loisirs))) theme = "L";
else if (args.getString(ARG_PAGE_CAT).equals( getString(R.string.astuces_transports))) theme = "T";
else theme = "";

这可能会解决您的问题，因为 == 运算符的结果将不一致，因为两个字符串可能指向也可能不指向同一对象。

ViewPager 不显示页面内容/更改视图后不刷新

ViewPager not showing page content / not refreshing after changing the view

android

android-layout

android-fragments

android-viewpager