Convert Code To RxJava2 Code

Question

I have been trying to understand RxJava 2 and how to work with it. I am also trying to understand RxJava by converting my code into an RxJava Code. But I still cant seem to understand it. I would really help if anyone can further explain me how to do re-code it.

This is the code I am trying to code in RxJava:

private static User getUserFomCursor(Cursor cursor) {
        if (cursor == null || cursor.getCount() == 0) {
            return null;
        } else {
            int myUserIDColumnIndex = cursor.getColumnIndex("_USER_ID");
            int usernameColumnIndex = cursor.getColumnIndex("USER_NAME");
            int userPasswordColumnIndex = cursor.getColumnIndex("USER_PASSWORD");
            int firstNameColumnIndex = cursor.getColumnIndex("FIRST_NAME");
            int middleNameColumnIndex = cursor.getColumnIndex("MIDDLE_NAME");
            int lastNameColumnIndex = cursor.getColumnIndex("LAST_NAME");
            int emailAddressColumnIndex = cursor.getColumnIndex("EMAIL_ADDRESS");
            int phoneNumberColumnIndex = cursor.getColumnIndex("PHONE_NUMBER");
            int profilePictureColumnIndex = cursor.getColumnIndex("PROFILE_PICTURE");
            try {
                User user = new User(
                        cursor.getInt(myUserIDColumnIndex), cursor.getString(usernameColumnIndex),
                        cursor.getString(userPasswordColumnIndex), cursor.getString(firstNameColumnIndex),
                        cursor.getString(middleNameColumnIndex), cursor.getString(lastNameColumnIndex),
                        cursor.getString(emailAddressColumnIndex), cursor.getString(phoneNumberColumnIndex),
                        cursor.getString(profilePictureColumnIndex));
                return user;
            } catch (Exception e) {
                return null;
            }
        }
    }

public ArrayList<User> getMyUsers() {
        User user = new User();
        ArrayList <User> userArrayList = new ArrayList<User>();
        open();
        try {
            Cursor cursor = userLocalDatabase.query("User", null, null, null, null, null, null);
            while (cursor.moveToNext()) {
                user = getUserFomCursor(cursor);
                userArrayList.add(user);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        close();
        return userArrayList;
    }

I was trying to make getMyUsers() method into an Observable. But I am still confused as to how to approach this problem. I would really appreciate it if someone will point me to the right direction. :)

Answer 1

You should be able to do something like:

public Observable<User> getMyUsers() {
    return Observable.create(subscriber -> {

        open(); 
        try { 
            Cursor cursor = userLocalDatabase.query("User", null, null, null, null, null, null);
            while (cursor.moveToNext()) {
                User user = getUserFomCursor(cursor);
                subscriber.onNext(user);
            } 
        } catch (SQLException e) { 
            e.printStackTrace(); 
        } 
        close(); 
        subscriber.onCompleted();
    });
}