使用getSupportFragmentManager（）時，findFragmentByTag（）返回null

Question

我正在使用支持庫ActionBar，因爲我使用的是較舊的最低SDK。在該活動中，我使用FragmentTabHost，因爲我有3個選項卡。 ActionBar還有一個SearchView，所以當進行搜索時，第三個選項卡會隨搜索結果切換出來。

我能夠從SearchView獲得輸入，但是當我有搜索結果時我無法切換出第三個選項卡。我用這作爲一個例子： Dynamically changing the fragments inside a fragment tab host?

我的問題是，當我嘗試去的第三個標籤的參考，我用getSupportFragmentManager（）findFragmentByTag（），返回的片段總是空。

我的基本容器，有助於在標籤交換多個片段：

public class BaseContainerFragment extends Fragment{ 

    public void replaceFragment(Fragment fragment, boolean addToBackStack) { 
     FragmentTransaction transaction = getChildFragmentManager().beginTransaction(); 
     if (addToBackStack) { 
      transaction.addToBackStack(null); 
     } 
     transaction.replace(R.id.container_framelayout, fragment); 
     transaction.commit(); 
     getChildFragmentManager().executePendingTransactions(); 
    } 

    public boolean popFragment() { 
     //Log.e("test", "pop fragment: " + getChildFragmentManager().getBackStackEntryCount()); 
     boolean isPop = false; 
     if (getChildFragmentManager().getBackStackEntryCount() > 0) { 
      isPop = true; 
      getChildFragmentManager().popBackStack(); 
     } 
     return isPop; 
    } 
} 

延伸BaseContainerFragment

public class LibraryContainerFragment extends BaseContainerFragment { 

    private boolean mIsViewInited; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     Log.e("test", "tab 1 oncreateview"); 
     return inflater.inflate(R.layout.container_fragment, null); 
    } 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 
     Log.e("test", "tab 1 container on activity created"); 
     if (!mIsViewInited) { 
      mIsViewInited = true; 
      initView(); 
//   setRetainInstance(true); 
     } 
    } 

    private void initView() { 
     Log.e("test", "tab 1 init view"); 

     replaceFragment(new LibraryFragment, false); 

    } 
} 

用於切換出片段（container_fragment.xml）的XML的容器：

<?xml version="1.0" encoding="utf-8"?> 
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/container_framelayout" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

</FrameLayout> 

我的主要活動：

public class BookSetup extends ActionBarActivity { 

    // For accessing SlidingMenu library 
    private SlidingMenu slidingMainMenu; 
    private FragmentTabHost mTabHost; 
    private SlidingMenu slidingContextMenuFavourites; 
    private SlidingMenu slidingContextMenuMyPrayerBook; 
    private SlidingMenu slidingContextMenuLibrary; 
    private android.support.v4.app.FragmentManager fragmentManager; 

    LibraryContainerFragment libraryContainerFragment; 


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


     // Settings for the clickable top-left button in the action bar 
     android.support.v7.app.ActionBar bar = getSupportActionBar(); 

     bar.setDisplayHomeAsUpEnabled(false); 
     bar.setHomeButtonEnabled(true); 
     bar.setIcon(R.drawable.main_menu); 

     // Setting up tabbed navigation 
     bar.setDisplayShowTitleEnabled(false); 


     // Setting up tabs  
     fragmentManager = getSupportFragmentManager(); 
     mTabHost = (FragmentTabHost)findViewById(android.R.id.tabhost); 
     mTabHost.setup(this, fragmentManager, R.id.realtabcontent); 



     // Add tabs 
     mTabHost.addTab(mTabHost.newTabSpec("Favourites").setIndicator(getString(R.string.favourites)), 
       FavouritesFragment.class, null); 

     mTabHost.addTab(mTabHost.newTabSpec("My Book").setIndicator(getString(R.string.my_book)), 
       MyBookFragment.class, null); 
     mTabHost.addTab(mTabHost.newTabSpec("Library").setIndicator(getString(R.string.library)), 
       LibraryContainerFragment.class, null); 

     mTabHost.setCurrentTab(2); 


     //mTabHost. 

     // Creates a sliding animation when activity is started 
     overridePendingTransition(R.anim.slide_in_from_right, R.anim.slide_out_to_left); 
    } 



     @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 

     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main_menu_with_search_context_menu, menu); 


     SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE); 
     //SearchView searchView = (SearchView) menu.findItem(R.id.action_search).getActionView(); 



     final MenuItem searchMenuItem = menu.findItem(R.id.action_search); 
     searchView = (android.support.v7.widget.SearchView) MenuItemCompat.getActionView(searchMenuItem); 
     //searchView = (SearchView)menu.findItem(R.id.action_search).getActionView(); 
     searchView.setSearchableInfo(searchManager 
       .getSearchableInfo(getComponentName())); 
     //searchView.requestFocus(); 
     searchView.requestFocusFromTouch(); 

     //searchView.setIconifiedByDefault(true); 


     // Listener for the search input found in the action bar, when the magnifying glass is 
     // clicked 
     searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() { 

      // Activated when a search string is submitted 
      @Override 
      public boolean onQueryTextSubmit(String query) { 
       // TODO : query is the text from the search view after you clicked search 

       if(query != null){ 


        // If results are found, then switch the fragments 
        if(!sectionsFound.isEmpty()){ 

         // Initialize the search fragment and send bundles of data to it 
         SearchLibraryResultFragment fragment = new SearchLibraryResultFragment(); 
         Bundle bundle = new Bundle(); 
         bundle.putParcelableArrayList("values", 
           (ArrayList<? extends Parcelable>) sectionsFound); 
         bundle.putStringArrayList("names", sectionNames); 
         fragment.setArguments(bundle); 

         mTabHost.setCurrentTab(2); 
         libraryContainerFragment = (LibraryContainerFragment)fragmentManager.findFragmentByTag("Library"); 


         ((BaseContainerFragment) libraryContainerFragment.getParentFragment()).replaceFragment(fragment,true); 


       return true; 
      } 


     }); 

    } 
} 

這是始終處於BookSetup.java返回null行：您正在使用ChildFragmentManager，以取代Fragments權

((BaseContainerFragment) libraryContainerFragment.getParentFragment()).replaceFragment(fragment,true); 

Answer 1

？

這可能是你的問題，而不是

libraryContainerFragment = (LibraryContainerFragment)fragmentManager.findFragmentByTag("Library"); 

使用

libraryContainerFragment = (LibraryContainerFragment) getChildFragmentManager().findFragmentByTag("Library");