Question

我一直在开发一个使用导航抽屉和View寻呼机的应用。我正面临着让它正常工作的问题。问题：当我启动应用程序时，摘要选项从导航抽屉和Viewpager中选择，在UI上显示3个页面。这里一切正常。当我从导航抽屉中选择其他选项并再次返回“摘要”选项时，视图寻呼机中的视图会丢失。

CODE：

为了从导航抽屉中选择不同的选项，我写了以下代码：

@Override
public void onNavigationDrawerItemSelected(int position) {
    Log.d("DataAnalyticActivity", "onNavigationDrawerItemSelected ");
    FragmentManager fragmentManager = getFragmentManager();
    Fragment fragment = new Fragment();
    switch (position) {
    case 0:
        fragment = SummaryFragment.newInstance();

        break;

    case 1:
        fragment = SettingsFragment.newInstance();
        break;

    case 2:
        fragment = HelpFragment.newInstance();
        break;
    }


    // This code is for handling orientation change 
    // After orientation change it will check for existing fragment and 
    // if it of same class of previous orientation it will use it.
    if (!mIsUserInitiatedNavItemSelection)
    {
        mIsUserInitiatedNavItemSelection = true;
        Fragment existingFragment = getFragmentManager().findFragmentById(R.id.container);
        Log.d("DataAnalyticActivity", "inisde " + existingFragment);
        if (existingFragment != null && existingFragment.getClass().equals(fragment.getClass()))
        {
            return ;  
        }
    }


    fragmentManager.beginTransaction()
    .replace(R.id.container, fragment)
    .addToBackStack(null)
    .commit();

}

SummaryFragment.java文件

public class SummaryFragment extends Fragment {

    SummaryPagerAdapter mSummaryPagerAdapter;
    static SummaryFragment summaryFrag ;
    ViewPager mViewPager;


    public static SummaryFragment newInstance() {
        if (summaryFrag == null) {
            summaryFrag = new SummaryFragment();
        }
        return summaryFrag;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("SummaryFragment", "onCreate " + savedInstanceState);
        setRetainInstance(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        Log.d("SummaryFragment", "onCreateView " + savedInstanceState);

        View v = inflater.inflate(R.layout.activity_summary, container, false);

        mSummaryPagerAdapter = new SummaryPagerAdapter(getFragmentManager());

        mViewPager = (ViewPager) v.findViewById(R.id.pager);
        mViewPager.setAdapter(mSummaryPagerAdapter);

        return v;

    }
}

SummaryPagerAdapter.java文件

public class SummaryPagerAdapter extends FragmentPagerAdapter {

    DailyFragment dailyFragment;
    WeeklyFragment weeklyFragment;
    MonthlyFragment monthlyFragment;

    public SummaryPagerAdapter(FragmentManager fm) {
        super(fm);
        Log.d("SummaryPager", "SummaryPagerAdapter");

        dailyFragment = DailyFragment.newInstance();
        weeklyFragment = WeeklyFragment.newInstance();
        monthlyFragment = MonthlyFragment.newInstance();

    }

    @Override
    public Fragment getItem(int position) {
        Log.d("SummaryPager", "getItem");
        switch (position) {
        case 0:
            return dailyFragment; 
        case 1:
            return weeklyFragment; 
        case 2:
            return monthlyFragment; 

        }
        return null;
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {

        switch (position) {
        case 0:
            return "Daily";
        case 1:
            return "Weekly";
        case 2:
            return "Monthly";
        }
        return null;
    }
}

DailyFragment，WeeklyFragment和MonthlyFragment类似于下面描述的DailyFragment。他们内部有不同的观点，这只是差异。 DailyFragment.java

public class DailyFragment extends Fragment implements HttpCallTask.OnHttpCallTaskListener {

    Button dateButton;
    ListView list;
    static DailyFragment dailyfaragment;

    public DailyFragment() {

    }

    public static DailyFragment newInstance() {
        if (dailyfaragment == null) {
            Log.d("DailyFragment", "newInstance");
            dailyfaragment = new DailyFragment();
        }

        return dailyfaragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("DailyFragment", "onCreate " + savedInstanceState);
        setRetainInstance(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        Log.d("DailyFragment", "onCreateView " + savedInstanceState + " check " + check);
        View rootView = inflater.inflate(R.layout.fragment_daily,
            container, false);

        list = (ListView) rootView.findViewById(R.id.list);
        dateButton = (Button) rootView.findViewById(R.id.button_date);
        return rootView;
    }
}

请帮助解决此问题。我花了很多时间研究它。提前谢谢。

Answer 1

由于ViewPager位于另一个片段中，导致嵌套片段＆＃39;，您需要用getChildFragments()替换适配器的参数，即

mSummaryPagerAdapter = new SummaryPagerAdapter(getChildFragmentManager());

getChildFragmentManager()仅适用于API leval＆gt; = 17，但存在于支持库中。

也可以参考我的问题。 ViewPager in NavigationDrawer failed to load the fragment content when navigation back from another drawer items

带有导航抽屉的ViewPager不可见

1 个答案: