PasswordStream.java

// Return true jika password yang diketik user < 6 karakter
Observable<Boolean> passwordStream = RxTextView.textChanges(etPassword)
        .map(new Func1<CharSequence, Boolean>() {
            @Override
            public Boolean call(CharSequence charSequence) {
                return !TextUtils.isEmpty(charSequence)
                        && charSequence.toString().trim().length() < 6;
            }
        });

Subscriber<Boolean> passwordSubscriber = new Subscriber<Boolean>() {
    @Override
    public void onCompleted() {
        Log.d("rx","Password stream completed");
    }

    @Override
    public void onError(Throwable e) {
        Log.d("rx",e.getMessage());
    }

    @Override
    public void onNext(Boolean passwordLessThanLimit) {
        Log.d("passwordSubscriber",String.valueOf(passwordLessThanLimit.booleanValue()));
        showPasswordMinimalAlert(passwordLessThanLimit.booleanValue());
    }
};

public void showPasswordMinimalAlert(boolean value){
        if(value) {
            textPasswordAlert.setText(getString(R.string.password_minimal_alert));
            textPasswordAlert.setVisibility(View.VISIBLE);
        } else {
            textPasswordAlert.setVisibility(View.GONE);
        }
}

passwordStream.subscribe(passwordSubscriber);