main.py

def get_message(cursor):
    return (
        cursor.getString(cursor.getColumnIndex('_id')),
        cursor.getString(cursor.getColumnIndex('address')),
        cursor.getString(cursor.getColumnIndex('body')))


def fetch_messages(lastindex):
    if platform == 'android':
        uriSms = Uri.parse('content://sms')
        cursor = context.getContentResolver().query(
            uriSms,
            ['_id', 'address', 'body', 'type', 'read'],
            "type=1", None,
            "date COLLATE LOCALIZED ASC limit 10 offset %s" % lastindex)

        if cursor and cursor.getCount():
            cursor.moveToFirst()
            yield get_message(cursor)
            while cursor.moveToNext():
                yield get_message(cursor)

        cursor.close()
        del(cursor)

    else:
        for i in range(10):
            yield ('%s' % i, 'message%s' % i)

Where did you created context?

if platform == 'android':
    from jnius import autoclass
    Uri = autoclass('android.net.Uri')
    Cursor = autoclass('android.database.Cursor')
    Service = autoclass('org.renpy.android.PythonService')
    context = Service.mService