Android : App Crash at start extending Activity to ActionBarActivity

Other problem.

This is My eclipse project:

http://i60.tinypic.com/1zoyhip.jpg
http://i61.tinypic.com/2rqhmo1.jpg

This My MainActivity

package com.radio.radiostar;


import android.app.Activity;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnBufferingUpdateListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Bundle;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

import java.io.IOException;



 public class MainActivity extends ActionBarActivity implements OnClickListener {

private final static String RADIO_STATION_URL = "http://178.32.137.180:8665/stream";


private Button buttonPlay;

private Button buttonStopPlay;

private MediaPlayer player;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    initializeUIElements();

    initializeMediaPlayer();
}


private void initializeUIElements() {

    buttonPlay = (Button) findViewById(R.id.buttonPlay);
    buttonPlay.setOnClickListener(this);

    buttonStopPlay = (Button) findViewById(R.id.buttonStopPlay);
    buttonStopPlay.setEnabled(false);
    buttonStopPlay.setOnClickListener(this);

}

public void onClick(View v) {
    if (v == buttonPlay) {
        startPlaying();
        Context context = getApplicationContext();
        CharSequence text = "In Connessione...";
        int duration = android.widget.Toast.LENGTH_LONG;
        android.widget.Toast toast = android.widget.Toast.makeText(context, text, duration);
        toast.show();
        Intent intent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.drawable.ic_launcher)
                .setContentTitle("Radio Star")
                .setContentText("In Diretta")
                .setContentIntent(pendingIntent);
        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify( 0, mBuilder.build());

    } else if (v == buttonStopPlay) {
        stopPlaying();

        Intent svc=new Intent(this, BackgroundSoundService.class);
        startService(svc);

    }
}

private void startPlaying() {
    if (player.isPlaying()) {
        buttonPlay.setVisibility(View.INVISIBLE);
    }
    buttonStopPlay.setEnabled(true);
    buttonPlay.setEnabled(false);
    buttonPlay.setVisibility(View.INVISIBLE);



    player.prepareAsync();

    player.setOnPreparedListener(new OnPreparedListener() {

        public void onPrepared(MediaPlayer mp) {
            player.start();
        }

    });

}

private void stopPlaying() {
    if (player.isPlaying()) {
        player.stop();
        player.release();
        initializeMediaPlayer();
        NotificationManager notificationManager = (NotificationManager) getApplicationContext().getSystemService(NOTIFICATION_SERVICE);
        notificationManager.cancel(0);
    }

    buttonPlay.setEnabled(true);
    buttonStopPlay.setEnabled(false);

    buttonPlay.setVisibility(View.VISIBLE);

}

private void initializeMediaPlayer() {
    player = new MediaPlayer();
    try {
        player.setDataSource(RADIO_STATION_URL);
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    player.setOnBufferingUpdateListener(new OnBufferingUpdateListener() {

        public void onBufferingUpdate(MediaPlayer mp, int percent) {

            Log.i("Buffering", "" + percent);
        }
    });
}

@Override
public void onBackPressed()
{
   moveTaskToBack(false);


}


};

Android Manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.radio.radiostar"
    android:versionCode="9"
    android:versionName="1.7.1" >

    <uses-sdk
        android:minSdkVersion="7"
        android:targetSdkVersion="21" />

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" 
            android:launchMode="singleTop">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Now, the problem: If i use this code, implementing v7 appcompat, and extending to ActionBarActivity, my app crash on start. I'm trying to use material design on my app, for the "non lollipop" devices, but it don't work.... Who can help me?