致命的异常：asynctask＃1 doInBackground

Im新的android编程，我不能找出哪个触发错误。我有这样的错误：致命的异常：asynctask＃1 doInBackground

10-29 02:34:17.989: E/AndroidRuntime(853): FATAL EXCEPTION: AsyncTask #1 
10-29 02:34:17.989: E/AndroidRuntime(853): java.lang.RuntimeException: An error occured while executing doInBackground() 
10-29 02:34:17.989: E/AndroidRuntime(853): at android.os.AsyncTask$3.done(AsyncTask.java:299) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.util.concurrent.FutureTask.setException(FutureTask.java:219) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.util.concurrent.FutureTask.run(FutureTask.java:239) 
10-29 02:34:17.989: E/AndroidRuntime(853): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.lang.Thread.run(Thread.java:841) 
10-29 02:34:17.989: E/AndroidRuntime(853): Caused by: java.lang.NullPointerException 
10-29 02:34:17.989: E/AndroidRuntime(853): at com.agf.tripassigner.CreateTripActivity$CreateTrip.doInBackground(CreateTripActivity.java:104) 
10-29 02:34:17.989: E/AndroidRuntime(853): at com.agf.tripassigner.CreateTripActivity$CreateTrip.doInBackground(CreateTripActivity.java:1) 
10-29 02:34:17.989: E/AndroidRuntime(853): at android.os.AsyncTask$2.call(AsyncTask.java:287) 
10-29 02:34:17.989: E/AndroidRuntime(853): at java.util.concurrent.FutureTask.run(FutureTask.java:234) 
10-29 02:34:17.989: E/AndroidRuntime(853): ... 4 more 
10-29 02:34:18.848: W/EGL_emulation(853): eglSurfaceAttrib not implemented 
10-29 02:34:19.909: E/WindowManager(853): Activity com.agf.tripassigner.CreateTripActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{41844d20 V.E..... R......D 0,0-456,144} that was originally added here 
10-29 02:34:19.909: E/WindowManager(853): android.view.WindowLeaked: Activity com.agf.tripassigner.CreateTripActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{41844d20 V.E..... R......D 0,0-456,144} that was originally added here 
10-29 02:34:19.909: E/WindowManager(853): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:345) 
10-29 02:34:19.909: E/WindowManager(853): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:239) 
10-29 02:34:19.909: E/WindowManager(853): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69) 
10-29 02:34:19.909: E/WindowManager(853): at android.app.Dialog.show(Dialog.java:281) 
10-29 02:34:19.909: E/WindowManager(853): at com.agf.tripassigner.CreateTripActivity$CreateTrip.onPreExecute(CreateTripActivity.java:80) 
10-29 02:34:19.909: E/WindowManager(853): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586) 
10-29 02:34:19.909: E/WindowManager(853): at android.os.AsyncTask.execute(AsyncTask.java:534) 
10-29 02:34:19.909: E/WindowManager(853): at com.agf.tripassigner.CreateTripActivity$1.onClick(CreateTripActivity.java:58) 
10-29 02:34:19.909: E/WindowManager(853): at android.view.View.performClick(View.java:4240) 
10-29 02:34:19.909: E/WindowManager(853): at android.view.View$PerformClick.run(View.java:17721) 
10-29 02:34:19.909: E/WindowManager(853): at android.os.Handler.handleCallback(Handler.java:730) 
10-29 02:34:19.909: E/WindowManager(853): at android.os.Handler.dispatchMessage(Handler.java:92) 
10-29 02:34:19.909: E/WindowManager(853): at android.os.Looper.loop(Looper.java:137) 
10-29 02:34:19.909: E/WindowManager(853): at android.app.ActivityThread.main(ActivityThread.java:5103) 
10-29 02:34:19.909: E/WindowManager(853): at java.lang.reflect.Method.invokeNative(Native Method) 
10-29 02:34:19.909: E/WindowManager(853): at java.lang.reflect.Method.invoke(Method.java:525) 
10-29 02:34:19.909: E/WindowManager(853): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
10-29 02:34:19.909: E/WindowManager(853): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
10-29 02:34:19.909: E/WindowManager(853): at dalvik.system.NativeStart.main(Native Method)

，这些都是我在班上的AsyncTask代码：

class CreateTrip extends AsyncTask<String, String, String> { 
     /** 
     * Before Sttarting Background thread Show Progress Dialog 
     */ 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      pDialog = new ProgressDialog(CreateTripActivity.this); 
      pDialog.setMessage("Creating Trip..."); 
      pDialog.setIndeterminate(false); 
      pDialog.setCancelable(true); 
      pDialog.show(); 

     } 
     /** 
     * Creating Trip 
     */ 
     protected String doInBackground(String... args) { 
      String plate = inputPlate.getText().toString(); 
      String customer = inputCustomer.getText().toString(); 
      String area = inputArea.getText().toString(); 
      String driver = inputDriver.getText().toString(); 

      //Building parameters 
      List<NameValuePair> params = new ArrayList<NameValuePair>(); 
      params.add(new BasicNameValuePair("plate", plate)); 
      params.add(new BasicNameValuePair("customer", customer)); 
      params.add(new BasicNameValuePair("area", area)); 
      params.add(new BasicNameValuePair("driver", driver)); 

      //getting JSON Object 
      // Note that create trip url accepts post method 
      JSONObject json = jsonParser.makeHttpRequest(url_create_trip, "POST", params); 

      // check log cat for response 
      Log.d("Create Response", json.toString()); 

      // check for success tag 
      try{ 
       int success = json.getInt(TAG_SUCCESS); 

       if (success == 1){ 
        //successfully created trip 
        Intent i = new Intent(getApplicationContext(), CreateTripActivity.class); 
        startActivity(i); 

        //closing this screen 
        finish(); 

       }else { 
        // failed to create trip 
       } 
      } catch (JSONException e){ 
       e.printStackTrace(); 
      } 
      return null; 
     } 
     /** 
     * After Completing background task Dismiss the progress Dialog 
     */ 
     protected void onPostExecute(String file_url) { 
      // dismiss the dialog once done 
      pDialog.dismiss(); 

     } 
    } 
}

请帮助：（（

来源

2013-10-29 user2930918

什么是第104行'CreateTripActivity.java'？ – Raghunandan

你在这里得到了NullPointerException：引起：java.lang.NullPointerException 10-29 02：34：17.989：E/AndroidRuntime（853）：at com.agf.tripassigner.CreateTripActivity $ CreateTrip.doInBackground（CreateTripActivity.java:104 ）'，在第104行检查你的文件，也许有些变量在使用前没有被初始化。 – user2652394

因为你必须在对话框中使用.cancel（），而不是.dismiss（） – Tejas

// try this way 
class CreateTrip extends AsyncTask { 
     ProgressDialog pDialog; 
     /** * Before Sttarting Background thread Show Progress Dialog */ 
     @Override protected void onPreExecute() { 
      super.onPreExecute(); 
      pDialog = new ProgressDialog(CreateTripActivity.this); 
      pDialog.setMessage("Creating Trip..."); pDialog.setIndeterminate(false); 
      pDialog.setCancelable(true); pDialog.show(); 
     } 
     /** 
     * Creating Trip 
     */ 
     protected String doInBackground(String... args) { 
      String plate = inputPlate.getText().toString(); 
      String customer = inputCustomer.getText().toString(); 
      String area = inputArea.getText().toString(); 
      String driver = inputDriver.getText().toString(); 

      //Building parameters 
      List<NameValuePair> params = new ArrayList<NameValuePair>(); 
      params.add(new BasicNameValuePair("plate", plate)); 
      params.add(new BasicNameValuePair("customer", customer)); 
      params.add(new BasicNameValuePair("area", area)); 
      params.add(new BasicNameValuePair("driver", driver)); 

      //getting JSON Object 
      // Note that create trip url accepts post method 
      JSONObject json = jsonParser.makeHttpRequest(url_create_trip, "POST", params); 

      // check log cat for response 
      Log.d("Create Response", json.toString()); 

      // check for success tag 
      try{ 
       int success = json.getInt(TAG_SUCCESS); 

       if (success == 1){ 
        // success to create trip 
        return "1"; 
       }else { 
        return "0"; 
        // failed to create trip 
       } 
      } catch (JSONException e){ 
       e.printStackTrace(); 
      } 
      return null; 
     } 
     /** 
     * After Completing background task Dismiss the progress Dialog 
     */ 
     protected void onPostExecute(String result) { 
      // dismiss the dialog once done 
      pDialog.dismiss(); 
      if(result!=null && result.equals("1")){ 
       // success to create trip 
       Intent i = new Intent(getApplicationContext(), CreateTripActivity.class); 
       startActivity(i); 
       finish(); 
      }else{ 
       // failed to create trip 
      } 

     } 
    }

来源

2013-10-29 06:50:54

但在op的代码中会导致NPE的原因是什么？ – Raghunandan

@Raghunanadan我想这是导致NPE Log.d（“Create Response”，json.toString（））;可能是json为null。 –

bcz你不能开始活动doInBackground（）。，doInBackground（）运行在ui线程之外，你可以在doInBackground（）中启动任何ui任务。 –

不要执行相关操作的UI doInBackgroungd()方法，只需将结果返回onPostExecute()，然后写入开始活动的代码即可

/** 
    * After Completing background task Dismiss the progress Dialog 
    */ 
    protected void onPostExecute(String result) { 
     // dismiss the dialog once done 
     pDialog.dismiss(); 
     if(result!=null && result.equals("1")){ 
      // success to create trip 
      Intent i = new Intent(getApplicationContext(), CreateTripActivity.class); 
      startActivity(i); 
      finish(); 
     }else{ 
      // failed to create trip 
     } 

    }

来源

2013-10-29 06:53:49 GrIsHu

致命的异常：asynctask＃1 doInBackground

回答

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