Flutter .infoconnected 这两个代码之间有什么区别吗

需要推送和移除的是什么，是否仅适用于多个设备？

https://firebase.google.com/docs/database/flutter/offline-capabilities#section-sample个

代码1:

final myConnectionsRef =
    FirebaseDatabase.instance.ref("users/joe/connections");
final lastOnlineRef =
    FirebaseDatabase.instance.ref("users/joe/lastOnline");
final connectedRef = FirebaseDatabase.instance.ref(".info/connected");
connectedRef.onValue.listen((event) {
  final connected = event.snapshot.value as bool? ?? false;
  if (connected) {
    final con = myConnectionsRef.push();
    con.onDisconnect().remove();
    lastOnlineRef.onDisconnect().set(ServerValue.timestamp);
    con.set(true);
  }
});

代码2:

final connectedListRef =
    FirebaseDatabase.instance.ref('.info/connected');
final userStatusDatabaseRef =
    FirebaseDatabase.instance.ref().child('users/joe');
connectedListRef.onValue.listen((event) {
  final connected = event.snapshot.value as bool? ?? false;
  if (connected) {
    userStatusDatabaseRef
        .set({'online': true, 'lastOnline': ServerValue.timestamp});
    userStatusDatabaseRef.onDisconnect().set({
      'online': false,
      'lastOnline': ServerValue.timestamp,
    });
  }
});