I have used the solutions provided in this answer Stopping & Starting music on incoming calls but can't figure out how to implement it in my code. This is what I did -
public class KameWidget extends AppWidgetProvider {
public static String ACTION_WIDGET_RECEIVER = "ActionReceiverWidget";
MediaPlayer mPlay;
Context mContext;
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager,
        int[] appWidgetIds) {
    RemoteViews remoteViews = new RemoteViews(context.getPackageName(),
            R.layout.main);
    Intent active = new Intent(context, KameWidget.class);
    active.setAction(ACTION_WIDGET_RECEIVER);
    PendingIntent actionPendingIntent = PendingIntent.getBroadcast(context,
            0, active, 0);
    remoteViews.setOnClickPendingIntent(R.id.IBWidget, actionPendingIntent);
    appWidgetManager.updateAppWidget(appWidgetIds, remoteViews);
}
@Override
public void onReceive(Context context, Intent intent) {
    final String action = intent.getAction();
    if (AppWidgetManager.ACTION_APPWIDGET_DELETED.equals(action)) {
        final int appWidgetId = intent.getExtras().getInt(
                AppWidgetManager.EXTRA_APPWIDGET_ID,
                AppWidgetManager.INVALID_APPWIDGET_ID);
        if (appWidgetId != AppWidgetManager.INVALID_APPWIDGET_ID) {
            this.onDeleted(context, new int[] { appWidgetId });
        }
    } else {
        if (intent.getAction().equals(ACTION_WIDGET_RECEIVER)) {
            mPlay = MediaPlayer.create(context, R.raw.kamehameha);
            mPlay.start();
            PhoneStateListener phoneStateListener = new PhoneStateListener() {
                @Override
                public void onCallStateChanged(int state,
                        String incomingNumber) {
                    if (state == TelephonyManager.CALL_STATE_RINGING
                            || state == TelephonyManager.CALL_STATE_OFFHOOK) {
                        mPlay.stop();
                    }
                    super.onCallStateChanged(state, incomingNumber);
                }
            };
            TelephonyManager mgr = (TelephonyManager) mContext
                    .getSystemService(Context.TELEPHONY_SERVICE);
            if (mgr != null) {
                mgr.listen(phoneStateListener,
                        PhoneStateListener.LISTEN_CALL_STATE);
            }
        } else {
        }
        super.onReceive(context, intent);
    }
  }
}