List return method returning an empty list (although list gets filled)

Question

I'm working on an Android app that uses an SQLite database to load data into a list and display it. I have a DatabaseHelper class that deals with CRUD methods for the database. I'm trying to find specific results from a given date, however, although my query returns expected results and fills up a list to return, I can't get this list returned in my Main activity.

My query method:

public List<Earthquake>getListByDate(LocalDate dateInput){

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor data = db.rawQuery("SELECT * FROM " + TABLE_NAME + " WHERE " + PUB_DATE + " = " + "'"+dateInput+"'", null);

        Log.e("Cursor", ""+data.getColumnCount());
        Log.e("QueryReturnList", ""+QueryReturnList(data));

        return QueryReturnList(data);
    }

Log:

E/Cursor: 12

E/returnList: [object, object, object...]

E/QueryReturnList: [object, object, object...]

QueryReturnList: (This method builds a list of objects from the input cursor)

    private List<Earthquake>QueryReturnList(Cursor data){

            List<Earthquake>returnList = new ArrayList<>();

            int titleIndex = data.getColumnIndex(TITLE_COL),
                    descIndex = data.getColumnIndex(DESC_COL),
                    //... ;

            while(data.moveToNext()){
                Earthquake e = new Earthquake(
                        data.getString(titleIndex),
                        data.getString(descIndex),
                        //... ;
                );
                returnList.add(e);
            }
            Log.e("returnList",""+returnList);
            return returnList;
        }

Log:

E/returnList: [object, object, object...]

As I log these results, they work as expected in the DatabaseHelper. The correct results are found, and QueryReturnList returns the expected list object.

---

However, when I call this list from my main activity and set it to a new list, it appears to be empty when I log it (or debug).

List<Earthquake>earthquakes = mDatabaseHelper.getListByDate(currentDateSelection);
Log.e("earthquakesByDate", ""+earthquakes);

Log:

E/returnList: []

E/earthquakesByDate: []

---

Why am I getting an empty list returned when it does return and log a filled list initially (in my DatabaseHelper)?

Note: It seems to log "returnList" and "QueryReturnList" multiple times while running in an unexpected order. Are the methods not having time to get all the data and return?

Answer 1

This line:

Log.e("QueryReturnList", ""+QueryReturnList(data));

calls QueryReturnList(data), so after this has finished, the cursor is iterated and because of:

while(data.moveToNext())

the cursor's pointer is after the last row.
Then this:

return QueryReturnList(data);

calls again QueryReturnList(data) and when it reaches this:

while(data.moveToNext())

it skips the loop because moveToNext() returns false.
So better drop this line:

Log.e("QueryReturnList", ""+QueryReturnList(data));

or rewrite getListByDate() like this:

public List<Earthquake>getListByDate(LocalDate dateInput){
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor data = db.rawQuery("SELECT * FROM " + TABLE_NAME + " WHERE " + PUB_DATE + " = " + "'"+dateInput+"'", null);
    Log.e("Cursor", ""+data.getColumnCount());
    List<Earthquake> list = QueryReturnList(data);
    Log.e("QueryReturnList", ""+list);
    return list;
}