當它作爲回調函數被調用時，菜單對象將變爲空

Question

我需要在進度條/工具欄中放置進度條。我可以通過以下鏈接進行操作（http://www.michenux.net/android-refresh-item-action-bar-circular-progressbar-578.html）。 但是我面臨的問題是爲了顯示和隱藏進度條，遵循我在此使用的回調設計模式。下面是代碼片段 -

public interface ICallBack { 
     void setRefreshActionButtonState(boolean b); 
    } 

    public class MyFragment extends Fragment implements View.OnClickListener, ICallBack { 
     private Menu optionsMenu; 

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

     @Override 
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
      webView = (WebView) findViewById(R.id.main_web); 

      webView.setWebViewClient(new MyWebViewClient());  
      webView.loadUrl("http://stackoverflow.com/"); 
     } 

     @Override 
     public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { 
      this.optionsMenu = menu; 
      getActivity().getMenuInflater().inflate(R.menu.menu_home_base, menu); 
     } 

     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 
      int id = item.getItemId(); 
      if (id == R.id.action_refresh) { 
       // Logic to load the webview again 
      } 
      return super.onOptionsItemSelected(item); 
     } 

     @Override 
     public void setRefreshActionButtonState(boolean refreshing) { 
      if (optionsMenu != null) { 
       final MenuItem refreshItem = optionsMenu.findItem(R.id.action_refresh); 
       if (refreshItem != null) { 
        if (refreshing) { 
         refreshItem.setActionView(R.layout.toolbar_indeterminate_progress); 
        } else { 
         refreshItem.setActionView(null); 
        } 
       } 
      } 
     } 
    } 


public class MyWebViewClient extends WebViewClient { 
     ICallBack callBack; 
     public MyWebViewClient(Activity context) { 
      callBack = new MyFragment(); 
     } 

     @Override 
     public boolean shouldOverrideUrlLoading(WebView view, String url) { 
      view.loadUrl(url); 
      return true; 
     } 

     @Override 
     public void onPageStarted(WebView view, String url, Bitmap favicon) { 
      super.onPageStarted(view, url, favicon); 
      callBack.setRefreshActionButtonState(true);//Showing the progressbar 
     } 

     @Override 
     public void onPageFinished(WebView view, String url) { 
      super.onPageFinished(view, url); 
      callBack.setRefreshActionButtonState(false);//Hiding the progressbar 
     } 
    } 

當setRefreshActionButtonState（）得到調用，然後我得到optionsMenu值空，導致無法顯示和隱藏進度。

有人可以幫助我弄清楚，在那裏我做錯了。

感謝，

Answer 1

你可以上傳XML在項目action_refresh是。問題可能在於findItem(R.id.action_refresh);