我试图获取数据以设置编辑文本框，但是当我启动活动时，致命异常 asynctask（由 NullPointer 异常引起）在我的“GetStudentDetails”类的 doinbackground 中抛出。
日志猫：-
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 类：-
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
}
}