Question

I want to create a two level ExpandableListView from a local database.

The group level I want to get the names from the database Category table

category_id | name
-------------------
    1       | NameOfCategory

the children level I want to get the names from the List table

list_id |   name   | foreign_category_id
--------------------------------
   1    | Listname |     1 

I’ve got a method in DatabaseDAO to get all the values from the table

public List<Category> getAllCategories()
{
    database = dbHelper.getReadableDatabase();
    List<Category> categories = new ArrayList<Category>();
    Cursor cursor = database.query(SQLiteHelper.TABLE_CATEGORY, null, null, null, null, null, null);

    cursor.moveToFirst();
    while(!cursor.isAfterLast())
    {
        Category category = cursorToCategory(cursor);
        categories.add(category);
        cursor.moveToNext();
    }
    cursor.close();

    return categories;
}

Now adding the names to the group level is easy I do it the following way:

ArrayList<String> groups;

for(Category c : databaseDao.getAllCategories())
            {
                groups.add(c.getName());
            }

Now I want to add the children to the ExpandableListView in the following array ArrayList<ArrayList<ArrayList<String>>> children;.

How do I get the children under the correct group name?
I think it has to do somenthing with groups.indexOf() but in the list table I only have a foreign category_id and not the actual name.

Answer 1

I’ve got the following which kinda works now.

I’ve created a rawQuery to get get the list names grouped with the category in rows.

public List<CategoryAndLists> getCategoryAndListNames()
{
    database = dbHelper.getReadableDatabase();
    List<CategoryAndLists> calList = new ArrayList<CategoryAndLists>();
    Cursor cursor = database.database.rawQuery("SELECT c.category_id, c.name, w.name FROM category AS c, lists AS w WHERE c.category_id = w.category_id ORDER BY c.category_id, w.name", null);

    cursor.moveToFirst();
    while(!cursor.isAfterLast())
    {
        CategoryAndLists categoryAndLists = new CategoryAndLists();
        categoryAndLists.setCategory(cursor.getString(0));
        categoryAndLists.setWishlist(cursor.getString(1));

        System.out.println(cursor.getString(0));
        System.out.println(cursor.getString(1));

        calList.add(categoryAndLists);

        cursor.moveToNext();
    }

    return calList;
}

And changed the loadData() method to the following:

private void loadData(){

        groups= new ArrayList<String>();
        children= new ArrayList<ArrayList<ArrayList<String>>>();

        int childrenIndex = 0;
        String lastCategory = "";


        for(Category c : databaseDao.getAllCategories())
        {
            if(!groups.contains(c.getName()))
            {
                groups.add(c.getName());
            }   
        }

        for(CategoryAndLists c : databaseDao.getCategoryAndListNames())
        {
            if(!children.contains(c.getWishlist()))
            {

                    if(lastCategory.equals(c.getCategory()))
                    {
                        childrenIndex++;
                        System.out.println("childrenIndex++ Called");
                    }
                    else
                    {
                        childrenIndex = 0;
                        System.out.println("childrenIndex = 0 Called");
                    } 

                //Get the groups ArrayList index id to add the children to
                int index = groups.indexOf(c.getCategory());

                System.out.println("INDEX CHILDRENINDEX: " +childrenIndex);

                children.add(new ArrayList<ArrayList<String>>());
                children.get(index).add(new ArrayList<String>());
                children.get(index).get(childrenIndex).add(c.getWishlist());

                childrenIndex++;
            }

        }

I’m going to do a couple of test runs but for now this works and I can’t think of any other solution, if someone has some input, it’s more than welcome.