我正在使用android中的一个小聊天室，现在当我设置自定义ListView时，我收到以下错误，有什么想法吗？
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)
已编辑：
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)
答案 0 :(得分：2)
您应该添加此行来初始化数组：
_roomData = jsonResult.getJSONArray("roomInfo");
//Add this line
jsonUsernameArray = new String[_roomData.length()];
答案 1 :(得分：1)
您的数组jsonUsernameArray永远不会被初始化。了解如何正确使用数组：
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html