仅当应用程序在Android API 28中运行时才运行定期工作

Question

我在API级别24和28中测试了相同的代码。使用API​​ 24，它每半小时显示一次通知，无论应用程序是在后台还是在前台甚至停止。但是使用API​​ 28时，仅在应用程序处于前台时才每半小时显示一次通知。当应用在后台运行时，它会随机随机显示通知。当应用程序停止时，它永远不会显示通知。如何创建在新版本的Android中显示常规通知的应用程序？我尝试使用WorkManger和NotificationManagerCompat。 WorkManager版本是最新的2.2.0。我测试的代码很简单，我是从官方文档中获得的：

class MainActivity : AppCompatActivity() {

    companion object {
        const val CHANNEL_ID = "channel_id_1"
    }

    class MyWorker(context: Context, workerParams: WorkerParameters) 
        : Worker(context, workerParams ) { 

        override fun doWork(): Result {
            var builder = NotificationCompat.Builder(applicationContext, MainActivity.CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_launcher_foreground)
                .setContentTitle("notificattion")
                .setContentText("notification")
                .setPriority(NotificationCompat.PRIORITY_DEFAULT)

            with(NotificationManagerCompat.from(applicationContext)) {
                // notificationId is a unique int for each notification that you must define
                notify(ThreadLocalRandom.current().nextInt(1, 1000), builder.build())
            }

            return Result.success()
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        createNotificationChannel()

        val myWork = PeriodicWorkRequestBuilder<MyWorker>(30, TimeUnit.MINUTES).build()

        WorkManager.getInstance(this).enqueueUniquePeriodicWork(
            "MyUniqueWorkName",
            ExistingPeriodicWorkPolicy.KEEP, myWork)
    }

    private fun createNotificationChannel() {
        // Create the NotificationChannel, but only on API 26+ because
        // the NotificationChannel class is new and not in the support library
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val importance = NotificationManager.IMPORTANCE_DEFAULT
            val channel = NotificationChannel(CHANNEL_ID, "channel mine", importance).apply {
                description = "description"
            }
            // Register the channel with the system
            val notificationManager: NotificationManager =
                getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            notificationManager.createNotificationChannel(channel)
        }
    }
}