jetpack rxjava demo

private void updateUserName() {
    String userName = mUserNameInput.getText().toString();
    // Disable the update button until the user name update has been done
    mUpdateButton.setEnabled(false);
    // Subscribe to updating the user name.
    // Re-enable the button once the user name has been updated
    mDisposable.add(mViewModel.updateUserName(userName)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(() -> mUpdateButton.setEnabled(true),
                    throwable -> Log.e(TAG, "Unable to update username", throwable)));
}

/**
 * Data Access Object for the users table.
 */
@Dao
public interface UserDao {

    /**
     * Get the user from the table. Since for simplicity we only have one user in the database,
     * this query gets all users from the table, but limits the result to just the 1st user.
     *
     * @return the user from the table
     */
    @Query("SELECT * FROM Users LIMIT 1")
    Flowable<User> getUser();

    /**
     * Insert a user in the database. If the user already exists, replace it.
     *
     * @param user the user to be inserted.
     */
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    Completable insertUser(User user);

    /**
     * Delete all users.
     */
    @Query("DELETE FROM Users")
    void deleteAllUsers();
}

Get the user name of the user.

/**
 * Get the user name of the user.
 *
 * @return a {@link Flowable} that will emit every time the user name has been updated.
 */
public Flowable<String> getUserName() {
    return mDataSource.getUser()
            // for every emission of the user, get the user name
            .map(user -> {
                mUser = user;
                return user.getUserName();
            });

}