Problem with Android Fun Facts code

package com.example.timmy.funfacts;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class FunFactsActivity extends AppCompatActivity {
    //private FactBook factBook = new FactBook();
    // declare variables
    private TextView factTextView;
    private Button showFactButton;
    //private RelativeLayout relativelayout;


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

        // Assign the views from the layout file to the corresponding variables
        factTextView = findViewById(R.id.factTextView);
        showFactButton = findViewById(R.id.showFactButton);

        OnClickListener listener = new OnClickListener() {
            @Override
            public void onClick(View v) {
                String fact = factBook.getFact();
                // update the screen with new fact
                factTextView.setText(fact);
            }
        };

        showFactButton.setOnClickListener(listener);
    }
}