FragmentStatePageAdapter阻止从onPageSelected方法调用片段onResume

Question

我在Activity TabLayout中有3个片段。第一个选项卡片段用于从用户获取数据并保存在数据库中。第2和第3个片段用于在ListView中显示此数据库数据。当有人在第一个片段中输入数据时，我必须立即在第二个和第三个片段中显示数据。所以我必须让我的片段一直刷新。我通过调用onResume（）方法中的每个片段来刷新OnPageSeceted方法中的这个片段数据。我的ViewPagerAdapter类扩展了FragmentStatePagerAdapter。问题是当我在ViewPagerAdapter中扩展FragmentStatePagerAdapter时，我的第二个片段onResume仅在应用启动时调用frist time。但第三个活动onResume每次都在调用。因此，我的第二个片段未显示更新的数据库数据。只有第3个活动正确显示新数据。但有趣的是，当我通过FragmentPagerAdpater扩展ViewPagerAdapter onResume在我更改片段时正确调用。为什么FragmentStatePagerAdpater阻止仅为第二个片段调用onResume（）？

注意： When my phone goes to sleep then after unlocking phone 2nd fragment calling onResume().

Project github链接：https://github.com/Forlonsunny/OnResumeInFragmentWithDataBase

SimpeTabActivity：

package com.theoaktroop.onresumeinfragmentwithdatabase;

import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import com.theoaktroop.onresumeinfragmentwithdatabase.fragments.QuestionnaireFragment;
import com.theoaktroop.onresumeinfragmentwithdatabase.fragments.SavedFormsFragment;
import com.theoaktroop.onresumeinfragmentwithdatabase.fragments.WelcomeFragment;


public class SimpleTabsActivity extends AppCompatActivity {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;
    ViewPagerAdapter adapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_simple_tabs);


        viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);
    }

    private void setupViewPager(final ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFragment(new WelcomeFragment(), "Welcome");
        adapter.addFragment(new QuestionnaireFragment(), "Question Fragment");
        adapter.addFragment(new SavedFormsFragment(), "Answer Fragment");
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                Fragment fragment = ((ViewPagerAdapter) viewPager.getAdapter()).getFragment(position);
                if ((position == 1 || position == 2) & fragment!=null) {
                  System.out.println("Form Tabs position= "+position);
                  fragment.onResume();
                }


            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

    }

}

ViewPagerAdapter：

package com.theoaktroop.onresumeinfragmentwithdatabase;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.view.ViewGroup;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Created by yeahi on 10/26/2015.
 */
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
    //Added
    private Map<Integer,String> fragmentTag;
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();
    //Added
    private FragmentManager fragmentManager;

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
        fragmentManager = manager;
        fragmentTag = new HashMap<Integer,String>();
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    //Added

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Object obj =  super.instantiateItem(container, position);
        if(obj instanceof Fragment){
            Fragment fragment = (Fragment) obj;
            String tag = fragment.getTag();
            fragmentTag.put(position,tag);
        }
        return obj;
    }
    //Added
    public Fragment getFragment(int position){
        String tag = fragmentTag.get(position);
        if(tag == null){
            return null;
        }
        return fragmentManager.findFragmentByTag(tag);
    }

    @Override
    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }
}

第二段：

package com.theoaktroop.onresumeinfragmentwithdatabase.fragments;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;

import com.theoaktroop.onresumeinfragmentwithdatabase.AnswerTabel.AnswerListAdapter;
import com.theoaktroop.onresumeinfragmentwithdatabase.AnswerTabel.AnswerModule;
import com.theoaktroop.onresumeinfragmentwithdatabase.AnswerTabel.AnswerTableDataBaseQuery;
import com.theoaktroop.onresumeinfragmentwithdatabase.R;

import java.sql.SQLException;
import java.util.List;


public class QuestionnaireFragment extends Fragment implements AdapterView.OnItemLongClickListener {


    private ListView mListView;
    private List<AnswerModule> mAnswerModuleList;
    public static AnswerListAdapter mAdapter2;
    private AnswerTableDataBaseQuery mAnswerTableDataBaseQuery;
    private Context context;
    private View rootView;
    long ePID = 0;

    public QuestionnaireFragment() {
        // Required empty public constructor
    }

    @Override
    public void onResume() {
        Log.i("bug", " Question i am here dude");
        context = getActivity();

        mListView = (ListView) rootView.findViewById(R.id.listview_saved_form);
        mAnswerTableDataBaseQuery = new AnswerTableDataBaseQuery(context);

        mAnswerModuleList = mAnswerTableDataBaseQuery.getAllAnswerSavedQuestion();

        mAdapter2 = new AnswerListAdapter(context, mAnswerModuleList);
        // Log.d("bug", "here");
        mListView.setAdapter(mAdapter2);


        mListView.setOnItemLongClickListener(this);

        super.onResume();
    }

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

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

        return rootView;
    }


    @Override
    public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
        ePID = id;
        showDeleteDialog();
        return true;
    }

    private void showDeleteDialog() {
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(context);
        alertDialog.setTitle("Delete Entry?")
                .setMessage("Are you sure you want to delete this entry?")
                .setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // continue with delete
                        try {
                            mAnswerTableDataBaseQuery.answerTableDeleteByAnswerId(ePID);
                        } catch (SQLException e) {
                            e.printStackTrace();
                        }
                        forRefresh();

                    }
                })
                .setNegativeButton(android.R.string.no, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // do nothing

                    }
                })
                .setIcon(android.R.drawable.ic_dialog_alert)
                .show();
    }

    public void forRefresh() {

        mAnswerTableDataBaseQuery = new AnswerTableDataBaseQuery(context);

        mAnswerModuleList = mAnswerTableDataBaseQuery.getAllAnswerSavedQuestion();

        mAdapter2 = new AnswerListAdapter(context, mAnswerModuleList);
        mListView.setAdapter(mAdapter2);

    }
}

第3个片段与第2个片段相同。