致命的異常AsyncTask＃3被拋出（由空指針異常引起）

Question

我試圖抓取數據來設置edittext框，但是當我啓動活動致命異常asynctask（由NullPointer異常引起）拋出在我的「GetStudentDetails」類的doinbackground ..

logcat的： -

08-30 14:15:49.412: E/AndroidRuntime(1655): FATAL EXCEPTION: AsyncTask #3 
08-30 14:15:49.412: E/AndroidRuntime(1655): java.lang.RuntimeException: An error occured while executing doInBackground() 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at android.os.AsyncTask$3.done(AsyncTask.java:299) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.util.concurrent.FutureTask.setException(FutureTask.java:219) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.util.concurrent.FutureTask.run(FutureTask.java:239) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.lang.Thread.run(Thread.java:856) 
08-30 14:15:49.412: E/AndroidRuntime(1655): Caused by: java.lang.NullPointerException 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at job.placed.placemeant.StudentEditProfile$GetStudentDetails.doInBackground(StudentEditProfile.java:126) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at job.placed.placemeant.StudentEditProfile$GetStudentDetails.doInBackground(StudentEditProfile.java:1) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at android.os.AsyncTask$2.call(AsyncTask.java:287) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  at java.util.concurrent.FutureTask.run(FutureTask.java:234) 
08-30 14:15:49.412: E/AndroidRuntime(1655):  ... 4 more 

studenteditprofile.class包含GetStudentDetails類： -

public class StudentEditProfile extends Activity implements 
    OnItemSelectedListener { 

EditText enrollment, ten, twelve, aggregate, backlog, pendingbacks; 
protected int mPos; 
protected String mSelection; 
Button btnSave; 

Spinner spinnerBranch; 

protected ArrayAdapter<CharSequence> mAdapter; 

// Progress Dialog 
private ProgressDialog pDialog; 
SessionManager session; 

// JSON parser class 
JSONParser jsonParser = new JSONParser(); 

// single product url 
private static final String url_student_detials = "http://192.168.0.2:80/placemeant/getstudent.php"; 

// url to update product 
private static final String url_update_student = "http://192.168.0.2:80/placemeant/update_student.php"; 

// JSON Node names 
private static final String TAG_SUCCESS = "success"; 

private static final String TAG_EMAIL = "email"; 
private static final String TAG_ENROLLMENT = "enrollment"; 
private static final String TAG_POSTS = "posts"; 
private static final String TAG_TEN = "ten"; 
private static final String TAG_TWELVE = "twelve"; 
private static final String TAG_AGGREGATE = "aggregate"; 
private static final String TAG_BACKLOG = "backlog"; 
private static final String TAG_PENDINGBACKS = "pendingbacks"; 
private static final String TAG_BRANCH = "branch"; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.editme); 

    // save button 
    btnSave = (Button) findViewById(R.id.bEDITSubmit); 

    spinnerBranch = (Spinner) findViewById(R.id.EDITspinnerBranch); 

    this.mAdapter = ArrayAdapter.createFromResource(this, 
      R.array.branch_array, 
      android.R.layout.simple_spinner_dropdown_item); 
    spinnerBranch.setAdapter(mAdapter); 

    spinnerBranch.setOnItemSelectedListener(this); 

    // Getting complete student details in background thread 
    new GetStudentDetails().execute(); 

    // save button click event 
    btnSave.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View arg0) { 
      // starting background task to update product 
      new SaveStudentDetails().execute(); 
     } 
    }); 

} 

/** 
* Background Async Task to Get complete product details 
* */ 
class GetStudentDetails extends AsyncTask<String, String, String> implements 
     OnItemSelectedListener { 

    /** 
    * Before starting background thread Show Progress Dialog 
    * */ 
    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     pDialog = new ProgressDialog(StudentEditProfile.this); 
     pDialog.setMessage("Loading student details. Please wait..."); 
     pDialog.setIndeterminate(false); 
     pDialog.setCancelable(true); 
     pDialog.show(); 
    } 

    /** 
    * Getting product details in background thread 
    * */ 
    protected String doInBackground(String... params) { 

     // updating UI from Background Thread 

     // Check for success tag 
     int success; 
     try { 
      HashMap<String, String> user = session.getUserDetails(); 

      String post_useremail = user.get(SessionManager.KEY_EMAIL); 
      // Building Parameters 
      List<NameValuePair> params1 = new ArrayList<NameValuePair>(); 
      params1.add(new BasicNameValuePair("email", post_useremail)); 

      // getting product details by making HTTP request 
      // Note that product details url will use GET request 
      JSONObject json = jsonParser.makeHttpRequest(
        url_student_detials, "POST", params1); 

      // check your log for json response 
      Log.d("Getting Student Details", json.toString()); 

      // json success tag 
      success = json.getInt(TAG_SUCCESS); 
      if (success == 1) { 
       // successfully received product details 
       JSONArray studentObj = json.getJSONArray(TAG_POSTS); // JSON 
                     // Array 

       // get first company object from JSON Array 
       final JSONObject setdetails = studentObj.getJSONObject(0); 

       runOnUiThread(new Runnable() { 
        public void run() { 
         enrollment = (EditText) findViewById(R.id.etEDITEnroll); 

         ten = (EditText) findViewById(R.id.etEDIT10); 
         twelve = (EditText) findViewById(R.id.etEDIT12); 
         aggregate = (EditText) findViewById(R.id.etEDITAggre); 
         backlog = (EditText) findViewById(R.id.etEDITBackLog); 
         pendingbacks = (EditText) findViewById(R.id.etEDITBackpending); 
         spinnerBranch = (Spinner) findViewById(R.id.EDITspinnerBranch); 

         // display product data in EditText 
         try { 
          enrollment.setText(setdetails 
            .getString(TAG_ENROLLMENT)); 
         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 

         try { 
          ten.setText(setdetails.getString(TAG_TEN)); 
         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
         try { 
          twelve.setText(setdetails.getString(TAG_TWELVE)); 
         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
         try { 
          aggregate.setText(setdetails 
            .getString(TAG_AGGREGATE)); 

         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
         try { 
          backlog.setText(setdetails 
            .getString(TAG_BACKLOG)); 

         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
         try { 
          pendingbacks.setText(setdetails 
            .getString(TAG_PENDINGBACKS)); 

         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
         try { 
          String setspin = setdetails 
            .getString(TAG_BRANCH); 

          int spinnerPosition = mAdapter 
            .getPosition(setspin); 
          spinnerBranch.setSelection(spinnerPosition); 

         } catch (JSONException e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
        } 
       }); 
      } else { 

      } 
     } 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 got all details 
     pDialog.dismiss(); 
    } 

    @Override 
    public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, 
      long arg3) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public void onNothingSelected(AdapterView<?> arg0) { 
     // TODO Auto-generated method stub 

    } 
} 

/** 
* Background Async Task to Save product Details 
* */ 
class SaveStudentDetails extends AsyncTask<String, String, String> { 

    /** 
    * Before starting background thread Show Progress Dialog 
    * */ 
    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     pDialog = new ProgressDialog(StudentEditProfile.this); 
     pDialog.setMessage("Saving details ..."); 
     pDialog.setIndeterminate(false); 
     pDialog.setCancelable(true); 
     pDialog.show(); 
    } 

    /** 
    * Saving product 
    * */ 
    protected String doInBackground(String... args) { 

     enrollment = (EditText) findViewById(R.id.etEDITEnroll); 

     ten = (EditText) findViewById(R.id.etEDIT10); 
     twelve = (EditText) findViewById(R.id.etEDIT12); 
     aggregate = (EditText) findViewById(R.id.etEDITAggre); 
     backlog = (EditText) findViewById(R.id.etEDITBackLog); 
     pendingbacks = (EditText) findViewById(R.id.etEDITBackpending); 
     spinnerBranch = (Spinner) findViewById(R.id.EDITspinnerBranch); 
     // getting updated data from EditTexts 
     String enroll = enrollment.getText().toString(); 

     String tenpercent = ten.getText().toString(); 
     String tewlvepercent = twelve.getText().toString(); 
     String aggregatesem = aggregate.getText().toString(); 
     String totalbacklog = backlog.getText().toString(); 
     String totalpending = pendingbacks.getText().toString(); 
     String branchselected = spinnerBranch.getSelectedItem().toString(); 
     HashMap<String, String> usere = session.getUserDetails(); 

     String postuseremail = usere.get(SessionManager.KEY_EMAIL); 
     // Building Parameters 
     List<NameValuePair> params = new ArrayList<NameValuePair>(); 
     params.add(new BasicNameValuePair(TAG_EMAIL, postuseremail)); 
     params.add(new BasicNameValuePair(TAG_ENROLLMENT, enroll)); 

     params.add(new BasicNameValuePair(TAG_TEN, tenpercent)); 
     params.add(new BasicNameValuePair(TAG_TWELVE, tewlvepercent)); 
     params.add(new BasicNameValuePair(TAG_AGGREGATE, aggregatesem)); 
     params.add(new BasicNameValuePair(TAG_BACKLOG, totalbacklog)); 
     params.add(new BasicNameValuePair(TAG_PENDINGBACKS, totalpending)); 
     params.add(new BasicNameValuePair(TAG_BRANCH, branchselected)); 

     // sending modified data through http request 
     // Notice that update product url accepts POST method 
     JSONObject json = jsonParser.makeHttpRequest(url_update_student, 
       "POST", params); 

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

      if (success == 1) { 
       // successfully updated 
       Intent i = getIntent(); 
       // send result code 100 to notify about product update 
       setResult(100, i); 
       finish(); 
      } else { 
       // failed to update details 
      } 
     } 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 product updated 
     pDialog.dismiss(); 
    } 
} 

@Override 
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, 
     long arg3) { 
    // TODO Auto-generated method stub 

} 

@Override 
public void onNothingSelected(AdapterView<?> arg0) { 
    // TODO Auto-generated method stub 

} 

} 

Answer 1

SessionManager session對象爲null。這似乎是你忘了實例化的一些自定義對象。