Android/SQLite get all items from one column

[Flanelman]

Hey Guys, so I want to get every category that is saved in my Database and save it into an ArrayList<String> in my main activity but I'm unsure of how to do so. Here's what I've tried:

 

//in the database manager class

 public ArrayList<String> get_all_Category()
    {
        SQLiteDatabase db = getWritableDatabase();
        
        ArrayList<String> all_categories = new ArrayList<String>();
        String dbString = "";
    
        String get_all_cat_query = " SELECT " + COLUMN_CATEGORY + " FROM " + TABLE_ITEMS + " WHERE 1 "; 

        Cursor cursor = db.rawQuery(get_all_cat_query, null);
        cursor.moveToFirst(); 
        while(!cursor.isAfterLast()) //while there is still data to check
        {
            if(cursor.getString(cursor.getColumnIndex("item_index"))!=null); 
            {
                dbString = cursor.getString(cursor.getColumnIndex("item_category"));
                all_categories.add(dbString);

            }
        }
        return all_categories;
    }

//in my main class

        db_manager = new databaseManager(this, null, null, 1); //create the database
        long index_value = db_manager.Get_Length_of_DB();
        int index = (int) index_value;
        if(index != 0) 
        {
            category_List.add(db_manager.get_all_Category().toString());
        }

 

I'm getting this error on this code which I don't really understand: 

 

Failed to read row 0, column -1 from a CursorWindow which has 2 rows, 1 columns.
java.lang.RuntimeException: Unable to start activity ComponentInfo{bit.powlz1.zak_mobileassignment/bit.powlz1.zak_mobileassignment.NewItemScreen}: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

Any help would be greatly appreciated!

[zwirek2201]

3 hours ago, Flanelman said:

Hey Guys, so I want to get every category that is saved in my Database and save it into an ArrayList<String> in my main activity but I'm unsure of how to do so. Here's what I've tried:
 

I'm getting this error on this code which I don't really understand: 

 

Failed to read row 0, column -1 from a CursorWindow which has 2 rows, 1 columns.
java.lang.RuntimeException: Unable to start activity ComponentInfo{bit.powlz1.zak_mobileassignment/bit.powlz1.zak_mobileassignment.NewItemScreen}: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

Any help would be greatly appreciated!

From the error I can imagine that cursor is trying to access a column with a negative index meaning it is not found. In lines:

 

if(cursor.getString(cursor.getColumnIndex("item_index"))!=null); 
{
  dbString = cursor.getString(cursor.getColumnIndex("item_category"));
  all_categories.add(dbString);
}

you're accessing two column's indexes by their names. One of the two "cursor.getColumnIndex" probably returns -1 (it did not find the column) and that's where you're getting the error. Your error also says that your cursor has 2 rows and 1 column, but you're trying to access columns "item_index" and "item_category" so one of them is surely missing.

[kva1992]

21 hours ago, Flanelman said:

Hey Guys, so I want to get every category that is saved in my Database and save it into an ArrayList<String> in my main activity but I'm unsure of how to do so. Here's what I've tried:

 

//in the database manager class

 public ArrayList<String> get_all_Category()
    {
        SQLiteDatabase db = getWritableDatabase();
        
        ArrayList<String> all_categories = new ArrayList<String>();
        String dbString = "";
    
        String get_all_cat_query = " SELECT " + COLUMN_CATEGORY + " FROM " + TABLE_ITEMS + " WHERE 1 "; 

        Cursor cursor = db.rawQuery(get_all_cat_query, null);
        cursor.moveToFirst(); 
        while(!cursor.isAfterLast()) //while there is still data to check
        {
            if(cursor.getString(cursor.getColumnIndex("item_index"))!=null); 
            {
                dbString = cursor.getString(cursor.getColumnIndex("item_category"));
                all_categories.add(dbString);

            }
        }
        return all_categories;
    }

//in my main class

        db_manager = new databaseManager(this, null, null, 1); //create the database
        long index_value = db_manager.Get_Length_of_DB();
        int index = (int) index_value;
        if(index != 0) 
        {
            category_List.add(db_manager.get_all_Category().toString());
        }

 

I'm getting this error on this code which I don't really understand: 

 

Failed to read row 0, column -1 from a CursorWindow which has 2 rows, 1 columns.
java.lang.RuntimeException: Unable to start activity ComponentInfo{bit.powlz1.zak_mobileassignment/bit.powlz1.zak_mobileassignment.NewItemScreen}: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

Any help would be greatly appreciated!

Also If I am not mistaken your sql query is limiting what is being return. For example, if i am not mistaken should should "SELECT * FROM" +TABLE_ITEMS, (the where clause is optional I would personally use when I need to filteror check/match conditions if not no point in having it.) This wall all results are returned. It may solve your issue then again I do not want to say that is the issue. Also I would recommend using .movetonext() instead of .isafterlast(). Personally this is how I would write the syntax

if(cursor.moveToFirst()){

do{

 if(cursor.getString(cursor.getColumnIndex("item_index"))!=null); 
            {
                dbString = cursor.getString(cursor.getColumnIndex("item_category"));
                all_categories.add(dbString);

            }

}while(cursor.moveToNext());

}

 

No idea if what i stated helps, but i hope it does. If I can help out anymore feel free to contact me.