Firebase Service Worker-如何让Service Worker实时监听Firebase的更改数据库？

Question

我有服务人员的代码。

self.addEventListener('activate', function(event) {

    database.on("child_added", function(snapshot) {
        var lists = firebase.database().ref('notify');
        lists.once('value', function(snapshot) {
            snapshot.forEach(function(childSnapshot) {
                var childKey = childSnapshot.key;
                var childData = childSnapshot.val();
                if(childData.show == true){
                    childData.show = false;
                    firebase.database().ref('notify/' + childKey).set(childData);

                    // Just notify show == true 
                    var notify = childData;
                    if (Notification.permission !== 'default'){
                        var title = notify.title;
                        var options = {
                            body: notify.body,
                            image: notify.image,
                            icon: notify.icon,
                            data: [
                                notify.link
                            ]
                        };
                        return self.registration.showNotification(title,
                            options);
                    }
                }else{
                    return;
                }
            });
        });

    });
});

self.addEventListener('notificationclick', function(event) {
    var click_action = event.notification.data[0];
    return clients.openWindow(click_action);
});

和index.html

<script>
        if ('serviceWorker' in navigator) {
            navigator.serviceWorker.register("{{url('/')}}" + '/firebase-messaging-sw.js').then((registration) => {
                messaging.useServiceWorker(registration);
            });
        }
</script>

当我打开正在运行的网站服务工作者并转发我的列表数据库时，但是当我关闭它时，它会更改状态“已激活并已停止”。 如何为工作人员实时运行并收听Firebase数据库上的更改提供服务？