创建一个后台服务，该服务启动后在一个新的线程中持续地以 1 秒间隔更新 通知栏，点击“启动服务”按钮后，服务启动，通知栏上出现图标并按照预设间隔交 替更新；点击“停止服务”按钮后，服务停止，通知栏图标被清除。 交替显示两个不同的图标，实验的代码

以下是一个实现上述功能的简单示例代码：

public class NotificationService extends Service {

    private static final int NOTIFICATION_ID = 1;
    private static final int INTERVAL = 1000; // 1秒间隔

    private NotificationManager mNotificationManager;
    private boolean mIsRunning;
    private boolean mIsSwitched; // 切换标记
    private Handler mHandler;

    private Runnable mUpdateRunnable = new Runnable() {
        @Override
        public void run() {
            switchNotificationIcon(); // 切换通知栏图标
            mHandler.postDelayed(this, INTERVAL);
        }
    };

    @Override
    public void onCreate() {
        super.onCreate();
        mNotificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        mHandler = new Handler();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        startForeground(NOTIFICATION_ID, createNotification()); // 启动前台服务
        startUpdate(); // 启动更新线程
        mIsRunning = true;
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        stopUpdate(); // 停止更新线程
        mNotificationManager.cancel(NOTIFICATION_ID); // 取消通知栏图标
        mIsRunning = false;
        super.onDestroy();
    }

    private void startUpdate() {
        mHandler.post(mUpdateRunnable);
    }

    private void stopUpdate() {
        mHandler.removeCallbacks(mUpdateRunnable);
    }

    private Notification createNotification() {
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.drawable.ic_notification_1)
                .setContentTitle(getString(R.string.notification_title))
                .setContentText(getString(R.string.notification_text))
                .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                .setOngoing(true);

        return builder.build();
    }

    private void switchNotificationIcon() {
        Notification notification = createNotification();
        if (mIsSwitched) {
            notification.icon = R.drawable.ic_notification_1;
        } else {
            notification.icon = R.drawable.ic_notification_2;
        }
        mNotificationManager.notify(NOTIFICATION_ID, notification);
        mIsSwitched = !mIsSwitched;
    }

    public static Intent getIntent(Context context) {
        return new Intent(context, NotificationService.class);
    }

    public boolean isRunning() {
        return mIsRunning;
    }
}

在按钮的点击事件中，可以通过以下代码启动或停止服务：

if (!mService.isRunning()) {
    startService(NotificationService.getIntent(this));
} else {
    stopService(NotificationService.getIntent(this));
}