Android: How to hide a button using Parse and an If Statement?

I'm using Parse to pass objects as strings and populate the text of 4 buttons for a quiz app.

Since the response options will vary, I've implemented an if statement to hide a button in case a string is not available.

Doing some trial runs, I can't get the button to hide when there isn't a string available.

Here's my code:

activity_quiz.xml

<Button
        android:layout_width="200dp"
        android:layout_height="40dp"
        android:text="Hello"
        android:id="@+id/firstOption"
        android:visibility="invisible"
        android:onClick="one"
        android:layout_gravity="center_horizontal"
        android:background="@drawable/shapes"
        android:textColor="#ebf4fa"
        android:layout_marginRight="30dp" />

Quiz.java

public class Quiz extends Activity {

TextView questionDisplay;
Button first;
String firstChoice;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_quiz);


    first = (Button) findViewById(R.id.firstOption);
    first.setTypeface(custom_font);

    firstChoice = first.getText().toString();

    ParseQuery<ParseObject> vote = ParseQuery.getQuery("quizAndroid");
        vote.findInBackground(new FindCallback<ParseObject>() {
           @Override
           public void done(List<ParseObject> items, ParseException e) {
            if (e == null) {
                for (ParseObject x : items) {
                    String display = x.getString("question");
                    questionDisplay.setText(display);
                        if (firstChoice.length() > 0) {
                            firstChoice = x.getString("optionone");
                            first.setVisibility(View.VISIBLE);
                            first.setText(firstChoice);

                        } else {

                            first.setVisibility(View.INVISIBLE);

                        }