I'm having a bit of a problem understanding what's happening here, so any help would be very much appreciated. I'm kind of new to the Android development.
Those are the errors I'm receiving:
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.example.benignfella.workorganizer, PID: 9956
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:300)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
Caused by: java.lang.NullPointerException
at com.example.benignfella.workorganizer.Fragment.RecordsListFragment$GetRecordsTask.doInBackground(RecordsListFragment.java:87)
at com.example.benignfella.workorganizer.Fragment.RecordsListFragment$GetRecordsTask.doInBackground(RecordsListFragment.java:77)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
and here's the class which is apparently problematic (which begins at the line 77, as described by RecordsListFragment.java:77)
public class GetRecordsTask extends AsyncTask<Void, Void, ArrayList<Records>> {
private final WeakReference<Activity> activityWeakRef;
public GetRecordsTask(Activity context) {
this.activityWeakRef = new WeakReference<Activity>(context);
}
@Override
protected ArrayList<Records> doInBackground(Void... arg0) {
ArrayList<Records> recordsArrayList = recordsDAO.getRecords();
return recordsArrayList;
}
@Override
protected void onPostExecute(ArrayList<Records> empList) {
if (activityWeakRef.get() != null && !activityWeakRef.get().isFinishing()) {
records = empList;
if (empList != null) {
if (empList.size() != 0) {
recordsListAdapter = new RecordsListAdapter(activity, empList);
recordsListView.setAdapter(recordsListAdapter);
} else {
Toast.makeText(activity, "No Records about records... wait wot m8?",
Toast.LENGTH_LONG).show();
}
}
}
}
}
Error points at the doInBackground method, more specifically, this line:
ArrayList<Records> recordsArrayList = recordsDAO.getRecords();
I've read something about conveying block of code to onPostExecute method, but I'm not sure how. It'd be great if someone could help me out on that one.
Edit: The proposed thread did not solve my problem the reason why I'm posting a question is that I'm not able to solve the problem myself.
According to the thread, NPE can occur because I'm assuming that object was created before the method was called, but wasn't that what I did here: public class GetRecordsTask extends AsyncTask<Void, Void, ArrayList<Records>>?
I genuinely do not understand what I'm doing wrong, so I'm really asking for some concrete help.
Edit 2: here is the RecordsDAO class in its entirety
public class RecordsDAO extends RecordsDBDAO {
public static final String RECORDS_ID_WITH_PREFIX = "records.id";
private static final String WHERE_ID_EQUALS = DatabaseHelper.ID + " =?";
private static final SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH);
//Constructor
public RecordsDAO(Context context) {
super(context);
}
public long save(Records records) {
//Use ContentValues to access database
ContentValues values = new ContentValues();
//Should I add the ID field as well?
values.put(DatabaseHelper.DESCRIPTION, records.getDescription());
values.put(DatabaseHelper.KEY_CREATED_AT, formatter.format(records.getDateofRecord()));
values.put(DatabaseHelper.STARTINGHOUR, records.getStart());
values.put(DatabaseHelper.FINISHINGHOUR, records.getFinish());
values.put(DatabaseHelper.COMMENTS, records.getComments());
return database.insert(DatabaseHelper.TABLE_RECORDS, null, values);
}
public long update(Records records) {
//Use ContentValues to access database
ContentValues values = new ContentValues();
values.put(DatabaseHelper.DESCRIPTION, records.getDescription());
values.put(DatabaseHelper.KEY_CREATED_AT, formatter.format(records.getDateofRecord()));
values.put(DatabaseHelper.STARTINGHOUR, records.getStart());
values.put(DatabaseHelper.FINISHINGHOUR, records.getFinish());
values.put(DatabaseHelper.COMMENTS, records.getComments());
long result = database.update(
DatabaseHelper.TABLE_RECORDS,
values,
WHERE_ID_EQUALS,
new String[] {
String.valueOf(records.getId())
}
);
return result;
}
public int deleteRecord(Records records) {
return database.delete(DatabaseHelper.TABLE_RECORDS,
WHERE_ID_EQUALS,
new String[] {
records.getId() + ""
});
}
public ArrayList<Records> getRecords() {
ArrayList<Records> records = new ArrayList<Records>();
String query = "SELECT " + RECORDS_ID_WITH_PREFIX + ", "
+ DatabaseHelper.DESCRIPTION + " ,"
+ DatabaseHelper.KEY_CREATED_AT + ", "
+ DatabaseHelper.STARTINGHOUR + ", "
+ DatabaseHelper.FINISHINGHOUR + ", "
+ DatabaseHelper.COMMENTS + " FROM "
+ DatabaseHelper.TABLE_RECORDS + " rec,"
+ DatabaseHelper.TABLE_LOCATIONS + " loc,"
+ DatabaseHelper.TABLE_TAGS + " tg WHERE rec."
+ DatabaseHelper.LOCATIONS_ID + " = loc." + DatabaseHelper.ID + " AND "
+ DatabaseHelper.TAGS_ID + " = tg." + DatabaseHelper.ID;
Cursor cursor = database.rawQuery(query, null);
while (cursor.moveToNext()) {
Records records1 = new Records();
records1.setId(cursor.getInt(0));
records1.setDescription(cursor.getString(1));
try {
records1.setDateofRecord(formatter.parse(cursor.getString(2)));
} catch (ParseException e) {
records1.setDateofRecord(null);
}
records1.setStart(cursor.getString(3));
records1.setFinish(cursor.getString(4));
records1.setComments(cursor.getString(5));
Locations locations = new Locations();
locations.setId(cursor.getInt(6));
locations.setLocation(cursor.getString(7));
Tags tags = new Tags();
tags.setId(cursor.getInt(8));
tags.setName(cursor.getString(9));
records1.setLocations(locations);
records1.setTags(tags);
records.add(records1);
}
return records;
}
public void loadTags() {
Tags tag = new Tags("Ljubljana, Faculty");
Tags tag1 = new Tags("Kranj, OpenLab");
Tags tag2 = new Tags("Ljubljana, Other");
Tags tag3 = new Tags("Kranj, Other");
List<Tags> tagsList = new ArrayList<Tags>();
tagsList.add(tag);
tagsList.add(tag1);
tagsList.add(tag2);
tagsList.add(tag3);
for (Tags tg : tagsList) {
ContentValues values = new ContentValues();
values.put(DatabaseHelper.TAGS, tg.getName());
database.insert(DatabaseHelper.TABLE_TAGS, null, values);
}
}
}
Solution
As @Mangal has pointed out, my mistake was in not initializing the RecordsDAO in its entirety, hence the Null Pointer Exception. The class which includes GetRecordsTask class did declare
RecordsDAO recordsDAO;
but this is incomplete initialization. In reality, it should be
RecordsDAO recordsDAO = new RecordsDAO(getActivity());
and that solved my issue. Big thanks for helping me out on that one, problem solved.
