保留viewpager片段android的状态

Question

我在一个片段中有一个viewpager,我在其中显示3个片段,但是当我第一次打开片段时它打开正常,当我移动到另一个片段并返回到viewpager片段时,它不显示视图寻呼机中的片段然后我必须更改手机的方向或继续滑动viewpager以显示隐藏的片段.

我用google搜索它,现在我知道我必须将标记设置为每个片段并使用findfragmentbytag方法检索片段但问题是当我尝试将标记设置为片段时

getSupportFragmentManager().beginTransaction().add(myFragment, "Some Tag").commit();

上面的行崩溃我的应用程序和logcat显示"不能将标签设置为片段",我知道我在做一些愚蠢的错误

这是我片段的完整代码.如果能指导我在哪里编写用于设置片段标记的代码,我将非常感激.提前致谢.

public class MatchesListingFragment extends Fragment implements ActionBar.TabListener {

    Context context;
    SectionsPagerAdapter mSectionsPagerAdapter;
    ViewPager mViewPager;
    ActionBar actionBar;
    Matchlistings db;
    Bundle savedInstanceState;

    Fragment livescore,fixture,results;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        this.savedInstanceState = savedInstanceState;
        db = new Matchlistings(getActivity());
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_matches, container, false);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        context = getActivity().getApplicationContext();

        if(savedInstanceState == null){
            livescore = new LiveScoreListingFragment();
            fixture = new FixturesListingFragment();
            results = new ResultsListingFragment();
        }

        if(!Constants.is_listing_refreshed){
            Log.i(MainActivity.TAG,"refreshing list");
            db.loadListingsFromServer().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        }

        actionBar = getActivity().getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        if(mSectionsPagerAdapter == null)
        mSectionsPagerAdapter = new SectionsPagerAdapter(getActivity().getSupportFragmentManager());
        mViewPager = (ViewPager) getView().findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }
        });


        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            Tab tb = actionBar.newTab()
            .setText(mSectionsPagerAdapter.getPageTitle(i))
            .setTabListener(this);

            actionBar.addTab(tb);

        }
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {
        Fragment fragment;

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

        @Override
        public Fragment getItem(int position) {
            switch(position){
            case 0:

                fragment = livescore;
                return fragment;
            case 1:
                fragment = fixture;
                return fragment;
            case 2:
                fragment = results;
                return fragment;
            case 3:
                fragment = new LiveScoreListingFragment();
                return fragment;
            }
            return null;
        }

        @Override
        public int getCount() {
            return 4;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
            case 0:
                return "LIVE";
            case 1:
                return "FIXTURES";
            case 2:
                return "RESULTS";
            case 3:
                return "HOT";
            }
            return null;
        }
    }

    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        actionBar.removeAllTabs();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    }

    @Override
    public void onTabReselected(Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onTabSelected(Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onTabUnselected(Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }

}

编辑:我现在试图通过标签从viewpager获取片段,而不是每次都创建新的片段.但问题仍然存在.

FixturesListingFragment fixture = (FixturesListingFragment) getActivity().getSupportFragmentManager().findFragmentByTag("android:switcher:"+R.id.pager+":1");
                if(fixture == null)
                    fixture = new FixturesListingFragment();

Answer 1

你试过用setOffscreenPageLimit吗？如果您有3个页面,则将其设置为2.这样即使应用程序处于谜语状态,也不会重新创建页面.这是链接

Answer 2

我通过仅使用 setOffScreenpageLimit(int) 来解决我拥有的附加选项卡数量的问题。

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new FragmentHome(), "Home");
    adapter.addFragment(new FragmentEProfile(), "e-Profile");
    adapter.addFragment(new FragmentResults(), "Results");
    adapter.addFragment(new FragmentOutpass(), "Outpass");
    viewPager.setAdapter(adapter);
    viewPager.setOffscreenPageLimit(3);
}

Answer 3

尝试保留实例，如下所述：

 @Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    //add this line
    setRetainInstance(true);

    context = getActivity().getApplicationContext();