Drawer NavigationView + Fragments with viewpager，如何避免在导航抽屉中的片段从一个切换到另一个时缓存数据？

Question

我在左侧有一个抽屉导航视图，它连接到具有不同 viewpager 的不同片段。结构如下

主要活动抽屉 NavigationView

| Fragment A  -- ViewPagerA ----Tab1 - Fragment1
                                Tab2 - Fragment2
|                               Tab3 - Fragment3

| Fragment B -- ViewPagerB ----Tab1 - Fragment4
                               Tab2 - Fragment5
|                              Tab3 - Fragment6

Fragment1-6 是列表视图片段。

问题是当我从Fragment A切换到Fragment B时，viewpager会从Fragment1缓存列表视图的内容，并尝试将缓存的内容显示给Fragment4的适配器。以至于我第一次从导航抽屉中切换片段时总是显示错误信息。

我的代码：

主要活动：

    public class MainActivity extends Activity {
  @InjectView(R.id.navigation_view) public NavigationView mNavigationView;
    @InjectView(R.id.drawerLayout) public DrawerLayout mDrawerLayout;
//......Layout injections..............///
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

  mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout, mToolbar,R.string.app_name,
                R.string.app_name){

             /** Called when a drawer has settled in a completely closed state. */
             public void onDrawerClosed(View view) {


super.onDrawerClosed(view);
         }

         /** Called when a drawer has settled in a completely open state. */
         public void onDrawerOpened(View drawerView) {
             super.onDrawerOpened(drawerView);
         }
     };

}


  public void setUpToggle()
    {


        mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

            // This method will trigger on item Click of navigation menu
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {


                if (menuItem.isChecked()) menuItem.setChecked(false);
                else menuItem.setChecked(true);

                //Closing drawer on item click
                mDrawerLayout.closeDrawers();

            switch (menuItem.getItemId()) {



                    case R.id.a_drawer:
                        startFragment(FragmentA.newInstance());
                        return true;

                   case R.id.b_drawer:
                        startFragment(FragmentB.newInstance());
                        return true;



     default:
   Toast.makeText(getApplicationContext(),"More things need to be added",Toast.LENGTH_SHORT).show();
                            return true;

                }
            }
        });


        mDrawerLayout.setDrawerListener(mDrawerToggle);


            mDrawerToggle.syncState();
}
}

片段A/B（完全相同的结构和布局）

public class TabFragment extends Fragment {

public static TabLayout tabLayout;
public static ViewPager viewPager;
public static int int_items = n; //n is any positive integer
private Context mContext;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    /**
     *Inflate tab_layout and setup Views.
     */

    View tabView =  inflater.inflate(R.layout.fragment_tab,null);
    tabLayout = (TabLayout) tabView.findViewById(R.id.tabs);
    viewPager = (ViewPager) tabView.findViewById(R.id.viewpager);

    viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));



    tabLayout.post(new Runnable() {
        @Override
        public void run() {
            tabLayout.setupWithViewPager(viewPager);

        }
    });
    return tabView;

}



class MyAdapter extends FragmentStatePagerAdapter{

    public MyAdapter(FragmentManager fm) {
        super(fm);


    }


    @Override
    public Fragment getItem(int position)
    {
        switch (position){
            case 0 : return  new Fragment1();//or Fragment4 5 6 here
            case 1 : return new  Fragment2();
            case 2 : return new  Fragment3();

            default:return new Fragment1();

        }
    }

    @Override
    public int getCount() {

        return int_items;

    }



    @Override
    public CharSequence getPageTitle(int position) {

        switch (position){
            case 0 :
                return "F1";
            case 1 :
                return  "F2";
            case 2 :
                return "F3";

        }
        return null;
    }
}

片段 1 - 6：

public class TabFocusFragmentextends extends Fragment
implements LoaderManager.LoaderCallbacks<Cursor>


{


private TabFocusAdapter mAdapter;
private List<E> mList;

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

    loadData();// never been executed,:(
    setHasOptionsMenu(true);
}

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

    loadData();
    setupRecyclerView();
    return view;
}

@Override
public void onResume() {
    super.onResume();
}



    @Override
    public void onLoadMore() {
if(NeedLoad)
       loadData();
    }

    private void loadData() {
        //RequestData
    ……
}


private void setupRecyclerView() {
  …...

}

@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    return new CursorLoader(mActivity, ContentProvider.createUri(E.class, null),
            null, null, null, null);
}

@Override //fragment starts here, why??
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {


    if (loadedList.size() > 0) {
     //crashes here …...

    if (!fullPacketLoaded) {
    }
}

@Override
public void onLoaderReset(Loader<Cursor> loader) {

}

如果新片段列表适配器不适合显示以前的内容，它将崩溃。

基于这个问题，您是否也对下面的问题有更好的解决方案？

Answer 1

终于修复了。

在我实现 LoaderManager 片段的 onCreate() 方法中，我这样做了

  getLoaderManager().initLoader(0, null, this);
        if(!getLoaderManager().getLoader(0).isReset()) {
            getLoaderManager().restartLoader(0, null, this);
        }

当新加载程序未正确激活时它可以工作。

Drawer NavigationView + Fragments with viewpager，如何避免在导航抽屉中的片段从一个切换到另一个时缓存数据？

Drawer NavigationView + Fragments with viewpager, how to avoid caching data when switching fragments in navigation drawer from one to another?

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