Android Build an Interactive Story App User Input Finding Views by IDs

I'm confused. What am I missing?

Am I not declaring this Button correctly?

MainActivity.java
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    protected Button exterminateButton;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Declare our view variables
        exterminateButton = (Button) findViewById(R.id.button1);
    }

}