onOptionsItemSelected（）方法不能在android

Question

中工作我想打開片段，當點擊菜單項，但它不工作，我不知道爲什麼。我試圖調試，但沒有任何幫助。如果有人能幫忙，我會很高興。預先感謝。

menu_main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:app="http://schemas.android.com/apk/res-auto" 
xmlns:tools="http://schemas.android.com/tools" 
tools:context="com.lineup.android.webbrowser.activities.MainActivity"> 
<item 
    android:id="@+id/clear_spinner" 
    android:icon="@drawable/ic_clear" 
    android:orderInCategory="50" 
    android:title="Clear" 
    app:showAsAction="collapseActionView|ifRoom" /> 
<item 
    android:id="@+id/action_menu" 
    android:icon="@drawable/ic_menu" 
    android:orderInCategory="200" 
    android:title="@string/menu" 
    app:showAsAction="always"> 
    <menu> 
     <item 
      android:id="@+id/downloads" 
      android:title="@string/downloads" 
      android:icon="@drawable/ic_download"/> 
     <item 
      android:id="@+id/draw" 
      android:title="@string/draw" 
      android:icon="@drawable/ic_paint"/> 
     <item 
      android:id="@+id/history" 
      android:title="@string/history" 
      android:icon="@drawable/ic_action_clock"/> 
     <item 
      android:id="@+id/settings" 
      android:title="@string/settings" 
      android:icon="@drawable/ic_settings"/> 
    </menu> 
</item> 
<item 
    android:id="@+id/action_search" 
    android:icon="@drawable/ic_search" 
    android:orderInCategory="100" 
    android:title="Search" 
    app:actionViewClass="android.support.v7.widget.SearchView" 
    app:showAsAction="collapseActionView|ifRoom" /> 

MainActivity.class

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    super.onCreateOptionsMenu(menu); 
    MenuInflater inflater = getMenuInflater(); 
    inflater.inflate(R.menu.menu_main, menu); 
    return true; 
} 


@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    int id = item.getItemId(); 
    switch (id) { 
     case R.id.downloads: 
      DownloadsFragment dlfrag = new DownloadsFragment(); 
      getSupportFragmentManager().beginTransaction() 
        .add(R.id.container, dlfrag) 
        .commit(); 
      return true; 
     default: 
      return super.onOptionsItemSelected(item); 
    } 
} 

DownloadsFragment.class

public class DownloadsFragment extends Fragment { 

private RecyclerView.Adapter adapter; 
private RecyclerView recyclerView; 
private RecyclerView.LayoutManager layoutManager; 
private ArrayList<String> listOfFiles=new ArrayList(); 

@Nullable 
@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 

    View view = inflater.inflate(R.layout.fragment_downloads, container, false); 

    Toolbar toolbar = (Toolbar)view.findViewById(R.id.downloads_toolbar); 
    toolbar.setTitle("Загрузки"); 
    ((AppCompatActivity)getActivity()).setSupportActionBar(toolbar); 
    ((AppCompatActivity)getActivity()). getSupportActionBar().setDisplayHomeAsUpEnabled(true); 

    recyclerView = (RecyclerView) view.findViewById(R.id.rv_downloads); 
    layoutManager = new LinearLayoutManager(getActivity()); 
    recyclerView.setLayoutManager(layoutManager); 

    adapter=new DownloadsAdapter(listOfFiles); 
    recyclerView.setAdapter(adapter); 

    return super.onCreateView(inflater, container, savedInstanceState); 
} 

}

Answer 1

return super.onCreateView(inflater, container, savedInstanceState);

你需要回到你這裏view

Answer 2

在onCreate方法添加setHasOptionsMenu(true);