如何在没有前台服务/警报管理器的情况下通过 Push Notif 在 Android 上播放警报声音，而不管设备已锁定或应用程序已被杀死？

Question

I am building an emergency security Android App. One of the important requirements is to play an Alarm sound from a push notification. This happens very rarely so most likely the App won't be running (maybe force stopped) and device might be locked or in sleep mode.

I am using FCM to send a push notification like this:

public class NotificationManager extends FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        playAlarmSound();

    }
}

And my Service looks like this:

<service
    android:name=".notification.NotificationManager"
    android:directBootAware="true"
    android:exported="true">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
        <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
    </intent-filter>
</service>

However, I only receive the notification if the Device is not locked. How can ensure that happens?

I have seen some posts to use an Alarm Manager & Foreground Services - but I don't want to be constantly running and draining battery for an infrequent (but extremely important) usecase?

Answer 1

I would recommend using custom sound so you can play the alarm sound. Set it to high priority so FCM will attempt to deliver it immediately even if the device is in Doze mode.

However, if you still consider using Alarm Manager, you can check out these posts about battery usage:

• Android: correct way to use AlarmManager without draining battery
• About alarmManager and perfomance/battery issue