Question

我想创建一个应用，每天在特定时间将整数值减1。为此，我使用的是BroadcastReceiver，该设备应该在上午12点激活。然后从BroadcastReceiver中，调用一个服务，该服务创建一个后台线程来修改数据库（MySQL数据库）中的值，然后关闭该服务。 问题是每天将值递减1次，而不是一次递减。这是代码：

清单

<receiver
    android:name=".myAlarm"
    android:enabled="true"
    android:exported="true"></receiver>

<service android:name=".myService"
    android:enabled="true"
    android:exported="true" />

主要

Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.HOUR_OF_DAY, 23);
        calendar.set(Calendar.MINUTE, 59);
        calendar.set(Calendar.SECOND, 0);

        AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent(Main.this, myAlarm.class);

        PendingIntent pendingIntent = PendingIntent.getBroadcast(this.context, 0, intent, 0);

        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT && Build.VERSION.SDK_INT >=  Build.VERSION_CODES.DONUT) {
            alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
                    AlarmManager.INTERVAL_DAY, pendingIntent);
        }
        else if(Build.VERSION.SDK_INT >=  Build.VERSION_CODES.KITKAT)
        {
            alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
                     AlarmManager.INTERVAL_DAY, pendingIntent);
        }

MyAlram（广播接收器）

public class myAlarm extends BroadcastReceiver {

    public void onReceive(Context context, Intent intent) {

            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                context.startForegroundService(new Intent(context.getApplicationContext(), myService.class));
            } else {
                context.startService(new Intent(context.getApplicationContext(), myService.class));
            }
    }

}

myService（服务）

public class myService extends Service{

    private DBWorkers mydb;
    private Thread backgroundThread;
    private Context context;
    private Boolean isRunning = false;

    /**
     * Called by the system when the service is first created.  Do not call this method directly.
     */
    @Override
    public void onCreate() {
        super.onCreate();
        this.context = this;
        this.backgroundThread = new Thread(myTask);

        if (Build.VERSION.SDK_INT >= 26) {
            String CHANNEL_ID = "my_channel_01";
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID,
                    "Channel human readable title",
                    NotificationManager.IMPORTANCE_DEFAULT);

            ((NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE)).createNotificationChannel(channel);

            Notification notification = new NotificationCompat.Builder(this)
                    .setContentTitle("")
                    .setContentText("").build();

            startForeground(1, notification);
        }
    }

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

    private Runnable myTask = new Runnable() {
        @Override
        public void run() {

            mydb = new DBWorkers(context);

            ArrayList<Worker> myList = new ArrayList<>(mydb.getAllWorkersService());
            ArrayList<Worker> newList = new ArrayList<>();

            //visa and work are the values I need to decrement daily
            for(Worker item : myList){
                int work = item.getWork(), visa = item.getVisa();

                if(visa > 0)
                {
                    visa = visa - 1;
                }
                else if(visa < 0)
                {
                    visa = 0;
                }

                if(work > 0)
                {
                    work = work - 1;
                }
                else if(work < 0)
                {
                    work = 0;
                }

                if(item.getVisa() != visa || item.getWork() != work){
                    newList.add(new Worker(item.getName(), visa, work, item.getId()));
                }
            }

            mydb.updateAllWorkers(newList);

            stopSelf();
        }
    };


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {


        if (!isRunning){
            isRunning = true;
            backgroundThread.start();
        }

        return START_STICKY;
    }

    /**
     * Called by the system to notify a Service that it is no longer used and is being removed.  The
     * service should clean up any resources it holds (threads, registered
     * receivers, etc) at this point.  Upon return, there will be no more calls
     * in to this Service object and it is effectively dead.  Do not call this method directly.
     */
    @Override
    public void onDestroy() {
        super.onDestroy();
    }
}

我还有其他几个问题：

1）对我来说，使用IntentService比普通服务更好吗？为什么？

2）我不知道下面的代码中发生了什么。我从在线答案中复制并粘贴了它，因为我的代码无法在我的手机上运行，并且我认为这是因为我的手机的操作系统是8.0，这是建议的解决方案。非常感谢您的帮助，向我解释一下。

String CHANNEL_ID = "my_channel_01";
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID,
                    "Channel human readable title",
                    NotificationManager.IMPORTANCE_DEFAULT);

            ((NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE)).createNotificationChannel(channel);

            Notification notification = new NotificationCompat.Builder(this)
                    .setContentTitle("")
                    .setContentText("").build();

            startForeground(1, notification);

3）我是否需要创建一个后台线程来运行此任务，还是因为该应用很可能会被杀死，所以它将在后台线程上自动执行？

非常感谢！

我希望我的服务每天工作一次，但它要多次工作

0 个答案: