自定义阵列适配器问题

我正在Android上的一个小型聊天室工作，现在当我设置自定义ListView我收到以下错误，有什么想法？自定义阵列适配器问题

public class roomActivity extends Activity 
{ 
    ListView mainListView; 
    ProgressDialog progressDialog; 
    String[] jsonUsernameArray, jsonMessageArray; 
    UpdateTask mTask = null; 

    @Override 
    public void onCreate(Bundle activityCycle) 
    { 
     super.onCreate(activityCycle); 
     setContentView(R.layout.room_layout); 
     mainListView = (ListView)findViewById(R.id.roomListView); 
     progressDialog = new ProgressDialog(this); 
     progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER); 
     progressDialog.setMessage("Fetech the data..."); 
     progressDialog.setCancelable(false); 
     progressDialog.show(); 
     mTask = new UpdateTask(); 
     mTask.execute(); 
    } 

    public class UpdateTask extends AsyncTask<Void, Void, JSONObject> 
    { 
     JSONArray _roomData = null; 
     protected void onPostExecute(JSONObject jsonResult) 
     { 
      try 
      { 
       _roomData = jsonResult.getJSONArray("roomInfo"); 
       for (int cnt = 0; cnt < _roomData.length(); cnt++) 
       { 
        JSONObject c = _roomData.getJSONObject(cnt); 
        jsonUsernameArray[cnt] = c.getString("name"); 
        jsonMessageArray[cnt] = c.getString("message"); 
       } 
      } 
      catch (JSONException e) 
      { 
       e.printStackTrace(); 
      } 
      mainListView.setAdapter(new customAdapter()); 
      progressDialog.dismiss(); 
     } 

     @Override 
     protected JSONObject doInBackground(Void... backgroundProcess) 
     { 
      UserFunctions userFunction = new UserFunctions(); 
      return userFunction.sendMessageToROOM("50", "Reza", "Salam dadash :-)", "89988");  
     } 
    } 

    public class customAdapter extends BaseAdapter 
    { 

     public int getCount() 
     { 
      return jsonMessageArray.length; 
     } 

     public Object getItem(int itemData) 
     { 
      return null; 
     } 

     public long getItemId(int itemPosition) 
     { 
      return itemPosition; 
     } 

     public View getView(int _position, View mainView, ViewGroup mainViewGroup) 
     { 
      LayoutInflater maniInFlater = getLayoutInflater(); 
      View _row = null; 
      TextView _usernameText, _messageText; 
      if (_position % 2 == 0) 
      { 
       _row = maniInFlater.inflate(R.layout.conversion_layout_odd, mainViewGroup, false); 
       _usernameText = (TextView)_row.findViewById(R.id.txtUsername); 
       _messageText = (TextView)_row.findViewById(R.id.txtMessage); 
       _usernameText.setText(jsonUsernameArray[_position]); 
       _messageText.setText(jsonMessageArray[_position]); 
      } 
      else 
      { 
       //do sth... 
      } 
      return _row; 
     } 

    } 
}

logcat的错误：

08-01 00:53:04.065: E/AndroidRuntime(17114): FATAL EXCEPTION: main 
08-01 00:53:04.065: E/AndroidRuntime(17114): java.lang.NullPointerException 
08-01 00:53:04.065: E/AndroidRuntime(17114): at com.merlingames.thermotalk.roomActivity$UpdateTask.onPostExecute(roomActivity.java:52) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at com.merlingames.thermotalk.roomActivity$UpdateTask.onPostExecute(roomActivity.java:1) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at android.os.AsyncTask.finish(AsyncTask.java:602) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at android.os.AsyncTask.access$600(AsyncTask.java:156) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at android.os.Handler.dispatchMessage(Handler.java:99) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at android.os.Looper.loop(Looper.java:137) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at android.app.ActivityThread.main(ActivityThread.java:4575) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at java.lang.reflect.Method.invokeNative(Native Method) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at java.lang.reflect.Method.invoke(Method.java:511) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556) 
08-01 00:53:04.065: E/AndroidRuntime(17114): at dalvik.system.NativeStart.main(Native Method)

编辑：

08-01 01:26:07.260: E/AndroidRuntime(18381): at android.app.ActivityThread.main(ActivityThread.java:4575) 
08-01 01:27:36.327: W/dalvikvm(18870): threadid=1: thread exiting with uncaught exception (group=0x40a561f8) 
08-01 01:27:36.327: E/AndroidRuntime(18870): FATAL EXCEPTION: main 
08-01 01:27:36.327: E/AndroidRuntime(18870): java.lang.NullPointerException 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.AbsListView.obtainView(AbsListView.java:2024) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.ListView.measureHeightOfChildren(ListView.java:1244) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.ListView.onMeasure(ListView.java:1155) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.View.measure(View.java:12723) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.RelativeLayout.measureChild(RelativeLayout.java:579) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:392) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.View.measure(View.java:12723) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.View.measure(View.java:12723) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.View.measure(View.java:12723) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2092) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.View.measure(View.java:12723) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1064) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.os.Handler.dispatchMessage(Handler.java:99) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.os.Looper.loop(Looper.java:137) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at android.app.ActivityThread.main(ActivityThread.java:4575) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at java.lang.reflect.Method.invokeNative(Native Method) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at java.lang.reflect.Method.invoke(Method.java:511) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556) 
08-01 01:27:36.327: E/AndroidRuntime(18870): at dalvik.system.NativeStart.main(Native Method)

来源

2012-07-31 iSun

什么是'roomActivity.java'第52行？ – kcoppock 2012-07-31 20:30:59

@kcoppock jsonUsernameArray [cnt] = c.getString（“name”）; – iSun 2012-07-31 20:45:39

然后'c'或'jsonUsernameArray'为空。最有可能的是'jsonUsernameArray'，因为你永远不会初始化它。 – kcoppock 2012-07-31 20:47:35

你应该加入这行来初始化数组：

_roomData = jsonResult.getJSONArray("roomInfo"); 

//Add this line 
jsonUsernameArray = new String[_roomData.length()];

来源

2012-07-31 20:52:50 kcoppock

谢谢，该错误已经消失，但我得到新的错误。请参阅我的编辑。 – iSun 2012-07-31 21:00:26

您正在'getItem（）'中返回'null'。所以是的，获得一个'View'会给你一个'NullPointerException'。返回数组中该位置的项目，而不是'null'。 – kcoppock 2012-07-31 21:02:15

不，你需要能够自己找出那种东西，它超出了原始问题的范围，我的评论基本上是伪代码。 – kcoppock 2012-07-31 21:11:22

您的数组jsonUsernameArray永远不会初始化。了解如何正确使用阵列：

http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html

来源

2012-07-31 20:56:55

谢谢，该错误已经消失，但我得到新的错误。请参阅我的编辑。 – iSun 2012-07-31 21:05:39

自定义阵列适配器问题

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