Apps Help debugging

package tutorial.helloviews;

import android.app.Activity;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class HelloViews extends Activity {
    boolean playing = false;
    MediaPlayer mp = MediaPlayer.create(this, R.raw.play);
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        Button button = (Button) findViewById(R.id.play);
        if(mp != null)
        {
        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v)
            {
                if(playing)
                {
                    mp.start();
                    playing = true;
                }
                else
                {
                    mp.stop();
                    playing = false;
                }
            }
        });}
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <Button android:id="@+id/play"
    android:text="Play"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    </Button>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="tutorial.helloviews"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".HelloViews"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>


</manifest>

Thread [<1> main] (Suspended (exception RuntimeException))    
    ActivityThread.performLaunchActivity(ActivityThread$ActivityRecord, Intent) line: 2585    
    ActivityThread.handleLaunchActivity(ActivityThread$ActivityRecord, Intent) line: 2679    
    ActivityThread.access$2300(ActivityThread, ActivityThread$ActivityRecord, Intent) line: 125    
    ActivityThread$H.handleMessage(Message) line: 2033    
    ActivityThread$H(Handler).dispatchMessage(Message) line: 99    
    Looper.loop() line: 123    
    ActivityThread.main(String[]) line: 4627    
    Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]    
    Method.invoke(Object, Object...) line: 521    
    ZygoteInit$MethodAndArgsCaller.run() line: 868    
    ZygoteInit.main(String[]) line: 626    
    NativeStart.main(String[]) line: not available [native method]