当应用程序关闭时，AlarmManager 不工作。这是为什么？

Question

美好的一天，我在我的 Android 应用程序中内置了一个计时器，它会在特定时间后发送一条消息。为此，我添加了一个带有未决意图的 AlarmManager。当我打开应用程序时，一切正常。它也适用于锁定屏幕。但是当我关闭应用程序时，挂起的意图不再被激活并且在给定时间没有消息出现。这是我的警报管理器：

Intent notifyIntent = new Intent(getContext(), MyReceiver.class);
 alarmManager = (AlarmManager) getContext().getSystemService(Context.ALARM_SERVICE);
        pendingIntent = PendingIntent.getBroadcast
                (getContext(), NOTIFICATION_ID, notifyIntent, PendingIntent.FLAG_UPDATE_CURRENT);

//when the alarm gets activated:

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                            alarmManager.setExact(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+delta_time2, pendingIntent);

                        }
 else {
                            alarmManager.set(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+delta_time2, pendingIntent);

                        }

在IntentService-Class（声明和调用通知的地方）：


Intent notifyIntent = new Intent(this, BigTextMainActivity.class);

      
        notifyIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);

        PendingIntent notifyPendingIntent =
                PendingIntent.getActivity(
                        this,
                        0,
                        notifyIntent,
                        PendingIntent.FLAG_UPDATE_CURRENT
                );



       
        Intent snoozeIntent = new Intent(this, BigTextIntentService.class);
        snoozeIntent.setAction(BigTextIntentService.ACTION_SNOOZE);

        PendingIntent snoozePendingIntent = PendingIntent.getService(this, 0, snoozeIntent, 0);
        NotificationCompat.Action snoozeAction =
                new NotificationCompat.Action.Builder(
                        R.drawable.ic_alarm_white_48dp,
                        "Snooze",
                        snoozePendingIntent)
                        .build();

        Intent dismissIntent = new Intent(this, BigTextIntentService.class);
        dismissIntent.setAction(BigTextIntentService.ACTION_DISMISS);

        PendingIntent dismissPendingIntent = PendingIntent.getService(this, 0, dismissIntent, 0);
        NotificationCompat.Action dismissAction =
                new NotificationCompat.Action.Builder(
                        R.drawable.ic_cancel_white_48dp,
                        "Dismiss",
                        dismissPendingIntent)
                        .build();

        NotificationCompat.Builder notificationCompatBuilder =
                new NotificationCompat.Builder(
                        getApplicationContext(), notificationChannelId);

        GlobalNotificationBuilder.setNotificationCompatBuilderInstance(notificationCompatBuilder);

        Notification notification = notificationCompatBuilder
                .setStyle(bigTextStyle)
                .setContentTitle(bigTextStyleReminderAppData.getContentTitle())
                .setContentText(bigTextStyleReminderAppData.getContentText())
                .setSmallIcon(R.drawable.ic_launcher)
                .setLargeIcon(BitmapFactory.decodeResource(
                        getResources(),
                        R.drawable.ic_alarm_white_48dp))
                .setContentIntent(notifyPendingIntent)
                .setDefaults(NotificationCompat.DEFAULT_ALL)
    
                .setColor(ContextCompat.getColor(getApplicationContext(), R.color.colorPrimary))


                .setCategory(Notification.CATEGORY_REMINDER)

                .setPriority(bigTextStyleReminderAppData.getPriority())

                .setVisibility(bigTextStyleReminderAppData.getChannelLockscreenVisibility())

             
                .addAction(snoozeAction)
                .addAction(dismissAction)

                .build();
//I am not quite shure, if I declared the foregroundservice for the notification at the right place
 
        startForeground(NOTIFICATION_ID, notification);
        mNotificationManagerCompat.notify(NOTIFICATION_ID, notification);
        Vibrator vibrator = (Vibrator) getApplication().getSystemService(Context.VIBRATOR_SERVICE);
        vibrator.vibrate(2 * 1000);

这些是我的权限：

<uses-permission android:name="android.permission.WAKE_LOCK"/>
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
    <uses-permission android:name="android.permission.VIBRATE"/>
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

感谢您的帮助！（顺便说一句，如果这个问题很愚蠢或者是因为我没有真正处理这个话题，只是想快速为我的应用程序发出警报，提前抱歉）

Answer 1

根据您的评论，警报似乎正常触发，但您的 BroadcastReceiver 在尝试启动 Service 时失败了。最可能的原因是您的设备对后台处理有额外的限制。一些设备，主要是低端设备和中国制造的设备，对允许运行“在后台”运行的应用程序有限制。如果您的应用不在允许应用的“白名单”中，Android 将不允许应用的组件在后台启动。

请参阅 https://developer.android.com/about/versions/oreo/background to read about background Service limitations and see 作为我讨论某些制造商限制后台处理的问题的答案示例。

注意：由于您无法在 Android 8 及更高版本上启动背景 Service（由于限制），您可以将 Service 作为前景 Service 启动，如下所示：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    context.startForegroundService(intent)
} else {
    context.startService(intent)
}

当应用程序关闭时，AlarmManager 不工作。这是为什么？

AlarmManager does not work when the app is closed. Why is that?

permissions

android

alarmmanager

android-pendingintent