arrayadapter中的Nullpointerexception。沒有找到視圖？

Question

我遇到了問題。每當我的應用嘗試打開一個片段時，我都會收到一個nullpointerexception。我認爲我的適配器沒有在我的片段中找到視圖。

以下是錯誤：

11-24 13:00:27.429: E/AndroidRuntime(31304): FATAL EXCEPTION: main 
11-24 13:00:27.429: E/AndroidRuntime(31304): java.lang.NullPointerException 
11-24 13:00:27.429: E/AndroidRuntime(31304): at android.widget.ArrayAdapter.init(ArrayAdapter.java:310) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at com.laurenswuyts.witpa.ListEventAdapter.<init>(ListEventAdapter.java:23) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at com.laurenswuyts.witpa.EventFragment.parseEventFromFQLResponse(EventFragment.java:154) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at com.laurenswuyts.witpa.EventFragment$2.onCompleted(EventFragment.java:119) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at com.facebook.Request$4.run(Request.java:1669) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at android.os.Handler.handleCallback(Handler.java:615) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at android.os.Handler.dispatchMessage(Handler.java:92) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at android.os.Looper.loop(Looper.java:137) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at android.app.ActivityThread.main(ActivityThread.java:4944) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at java.lang.reflect.Method.invokeNative(Native Method) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at java.lang.reflect.Method.invoke(Method.java:511) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805) 
11-24 13:00:27.429: E/AndroidRuntime(31304): at dalvik.system.NativeStart.main(Native Method) 

這裏是我的mainactivity：

public class EventFragment extends Fragment { 

    //Arraylist with event details 
    private static List<EventDetails> dataEvent; 

    //Adapter to put event details in listview 
    ListEventAdapter eventAdapter; 

    //Listview with the events 
    ListView lvEvents; 

    //To show Progress Circle 
    LinearLayout linearProgress; 

    private static final String TAG = "EventFragment"; 

    private static final int REAUTH_ACTIVITY_CODE = 100; 

    @Override 
    public View onCreateView(LayoutInflater inflater, 
      ViewGroup container, Bundle savedInstanceState) { 
     super.onCreateView(inflater, container, savedInstanceState); 
     View view = inflater.inflate(R.layout.event, 
       container, false); 
     linearProgress = (LinearLayout) view.findViewById(R.id.linProgress); 
     lvEvents = (ListView) view.findViewById(R.id.lvEvent); 
     // Check for an open session 
     Session session = Session.getActiveSession(); 
     if (session != null && session.isOpened()) { 
      // Get the user's data 
      ShowEventsFromFQL(); 

     } 
     return view; 
    } 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     uiHelper = new UiLifecycleHelper(getActivity(), callback); 
     uiHelper.onCreate(savedInstanceState); 


    } 


    public void ShowEventsFromFQL(){ 
     // Check for an open session 
     Session session = Session.getActiveSession(); 
     if (session != null && session.isOpened()) { 

      //Progressbar active   
      linearProgress.setVisibility(View.VISIBLE); 


      // Get the user's data 
      // ORDER BY attending_count DESC 
      String fqlQuery = "....."; 
      Bundle params = new Bundle(); 
      params.putString("q", fqlQuery); 
      Session session2 = Session.getActiveSession(); 
      Request request = new Request(session2, 
       "/fql",       
       params,       
       HttpMethod.GET,     
       new Request.Callback(){   
        public void onCompleted(Response response) { 
         Log.i(TAG, "Result: " + response.toString()); 
         parseEventFromFQLResponse(response);             
        }     
      }); 
      Request.executeBatchAsync(request); 
    }   
    } 

    public final void parseEventFromFQLResponse(Response response) 
    { 
     dataEvent = new ArrayList<EventDetails>(); 
     try 
     { 
      GraphObject graphObj = response.getGraphObject(); 
      JSONObject jsonObj = graphObj.getInnerJSONObject(); 
      JSONArray jsonArr = jsonObj.getJSONArray("data"); 

      for (int i = 0; i < (jsonArr.length()); i++) 
      { 
       JSONObject jObject = jsonArr.getJSONObject(i); 

        int attending_count = jObject.getInt("attending_count"); 
        String name = jObject.getString("name"); 
        String host = jObject.getString("host"); 
        String description = jObject.getString("description"); 
        String location = jObject.getString("location");   
        String start_time = jObject.getString("start_time"); 
        String end_time = jObject.getString("end_time"); 


        dataEvent.add(new EventDetails(attending_count, name, host, description, location, start_time, end_time)); 


      } 
     // if(dataEvent != null){ 

      eventAdapter = new ListEventAdapter(getActivity(), R.layout.event_item, dataEvent); 

      lvEvents.setAdapter(eventAdapter); 
      eventAdapter.notifyDataSetChanged(); 

      //Progressbar gone 
      linearProgress.setVisibility(View.GONE); 

     // } 
     } 
     catch (JSONException e) { 
      e.printStackTrace(); 
     } 
    } 


    @Override 
    public void onActivityResult(int requestCode, int resultCode, Intent data) { 
     super.onActivityResult(requestCode, resultCode, data); 
     if (requestCode == REAUTH_ACTIVITY_CODE) { 
      uiHelper.onActivityResult(requestCode, resultCode, data); 
     } 
    } 


    private void onSessionStateChange(final Session session, SessionState state, Exception exception) { 
     if (session != null && session.isOpened()) { 
      // Get the user's data. 
      ShowEventsFromFQL(); 

     } 
    } 

    private UiLifecycleHelper uiHelper; 
    private Session.StatusCallback callback = new Session.StatusCallback() { 
     @Override 
     public void call(final Session session, final SessionState state, final Exception exception) { 
      onSessionStateChange(session, state, exception); 
     } 
    }; 

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

    @Override 
    public void onSaveInstanceState(Bundle bundle) { 
     super.onSaveInstanceState(bundle); 
     uiHelper.onSaveInstanceState(bundle); 
    } 

    @Override 
    public void onPause() { 
     super.onPause(); 
     uiHelper.onPause(); 
    } 

    @Override 
    public void onDestroy() { 
     super.onDestroy(); 
     uiHelper.onDestroy(); 
    } 


} 

這裏是我的適配器：

public class ListEventAdapter extends ArrayAdapter<EventDetails> { 

    public ListEventAdapter(Context context, int textViewResourceId) { 
     super(context, textViewResourceId); 
     // TODO Auto-generated constructor stub 
    } 

    private List<EventDetails> eItems; 

    public ListEventAdapter(Context context, int resource, List<EventDetails> eItems) { 

     super(context, resource, eItems); 

     this.eItems = eItems; 
      } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     View v = convertView; 

     TextView txtAttending_count = null; 
     TextView txtName = null; 

     if (v == null) { 

      LayoutInflater vi; 
      vi = LayoutInflater.from(getContext()); 
      v = vi.inflate(R.layout.event_item, null);    
     } 

     txtAttending_count = (TextView) v.findViewById(R.id.attending_count); 
     txtName = (TextView) v.findViewById(R.id.name); 

     EventDetails p = eItems.get(position); 

     if (p != null) { 

      if (txtAttending_count != null) { 
       txtAttending_count.setText(""+p.getAttending_count()); 
      } 
      if (txtName != null) { 

       txtName.setText(""+p.getName()); 
      } 
     } 
     return v; 

    } 
} 

任何人可以幫我，因爲我真不」不知道問題是什麼。

Answer 1

如果我看的堆棧跟蹤我看到事情不對勁的構造 11-24 13:00:27.429: E/AndroidRuntime(31304): at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153) 11-24 13:00:27.429: E/AndroidRuntime(31304): at com.laurenswuyts.witpa.ListEventAdapter.<init>(ListEventAdapter.java:23)

望着ArrayAdapter的代碼調用到傳遞的上下文中提出： mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

所以我的猜測是context是null。

附加一個調試器並在您的構造函數中設置一個斷點以查看這個假設是否正確。

上下文是null，因爲getActivity()調用返回null。