Getting an error when clicking the choice button.

public class StoryActivity extends AppCompatActivity {

    private String name;
    private Story story;
    private ImageView storyImageView;
    private TextView storyTextView;
    private Button choice1Button;
    private Button choice2Button;

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

        storyImageView = (ImageView)findViewById(R.id.storyImageView);
        storyTextView = (TextView)findViewById(R.id.storyTextView);
        choice1Button = (Button)findViewById(R.id.choice1Button);
        choice2Button = (Button)findViewById(R.id.choice2Button);

        Intent intent = getIntent();
        name = intent.getStringExtra(getString(R.string.key_name));
        if(name.isEmpty() || name == null)
        {
            name = "Ahmed";
        }

        story = new Story();
        LoadPage(0);
    }

    private void LoadPage(int pageNumber) {
        final Page page = story.getPage(pageNumber);

        Drawable image = ContextCompat.getDrawable(this, page.getImageId());
        storyImageView.setImageDrawable(image);

        String pageText = getString(page.getTextId());
        pageText = String.format(pageText, name);
        storyTextView.setText(pageText);


        choice1Button.setText(page.getChoice1().getTextId());
        choice1Button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int nextPage = page.getChoice1().getNextPage();
                LoadPage(nextPage);
            }
        });
        choice2Button.setText(page.getChoice2().getTextId());
        choice2Button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int nextPage = page.getChoice2().getNextPage();
                LoadPage(nextPage);
            }
        });
    }
}