OnClickListener cannot be resolved to a type
<p>I'm diving into Java (this is day 1) and I'm trying to create a button that will trigger a notification when I click it...</p>

<p>This code is based off of the notification documentation <a href="http://developer.android.com/guide/topics/ui/notifiers/notifications.html" rel="nofollow">here</a>, and UI events documentation <a href="http://developer.android.com/guide/topics/ui/ui-events.html" rel="nofollow">here</a></p>

<pre><code>package com.example.contactwidget;

import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;

public class ContactWidget extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Button calc1 = (Button) findViewById(R.id.calc_button_1);
        calc1.setOnClickListener(buttonListener);

        setContentView(R.layout.main);
    }

    private static final int HELLO_ID = 1;

    //Error: OnClickListener cannot be resolved to a type
    private OnClickListener buttonListener = new OnClickListener() {
        public void onClick (View v) {
            String ns = Context.NOTIFICATION_SERVICE;
            NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);

            int icon = R.drawable.icon;
            CharSequence ticketBrief = "Button Pressed Brief";
            CharSequence ticketTitle = "Button pressed";
            CharSequence ticketText = "You pressed button 1";
            long when = System.currentTimeMillis();

            Notification notification = new Notification(icon, ticketBrief, when);

            Intent notificationIntent = new Intent(this, ContactWidget.class);
            PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);

            notification.setLatestEventInfo(getApplicationContext(), ticketTitle, ticketText, contentIntent);

            mNotificationManager.notify(HELLO_ID, notification);
        }
    }
}
</code></pre>

<p>I'm running into a problem: <code>OnClickListener cannot be resolved to a type</code>.  The problem here is that I don't see any problems with my code in relation to the example I'm using</p>
