android - Firebase 监听器在空闲时间后无法识别或恢复连接

Question

我的项目是识别客户端是在线还是离线。我使用 Android-Firebase 文档中提供的代码，它在“.info/connected”中使用 EventListener。

// since I can connect from multiple devices, we store each connection instance separately
// any time that connectionsRef's value is null (i.e. has no children) I am offline
final FirebaseDatabase database = FirebaseDatabase.getInstance();
final DatabaseReference myConnectionsRef = database.getReference("users/joe/connections");

// stores the timestamp of my last disconnect (the last time I was seen online)
final DatabaseReference lastOnlineRef = database.getReference("/users/joe/lastOnline");

final DatabaseReference connectedRef = database.getReference(".info/connected");
connectedRef.addValueEventListener(new ValueEventListener() {
  @Override
  public void onDataChange(DataSnapshot snapshot) {
    boolean connected = snapshot.getValue(Boolean.class);
    if (connected) {
      DatabaseReference con = myConnectionsRef.push();

      // when this device disconnects, remove it
      con.onDisconnect().removeValue();

      // when I disconnect, update the last time I was seen online
      lastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP);

      // add this device to my connections list
      // this value could contain info about the device or a timestamp too
      con.setValue(Boolean.TRUE);
    }
  }

  @Override
  public void onCancelled(DatabaseError error) {
    System.err.println("Listener was cancelled at .info/connected");
  }
});

此方法正确识别用户何时终止或重新打开应用程序，或者何时在 Internet 上发生轻微断开连接。但是，我做了一个测试，关闭设备的 Wifi 2 分钟，在 Firebase 数据库中识别为未连接，但是当我打开 Wifi，恢复互联网连接时，Firebase 无法识别 Activity 连接，看起来好像用户仍然处于非 Activity 状态。

这段代码 fragment 被插入到我的 MainActivity 的 onCreate 方法中。

谁能告诉我为什么会这样？

编辑: 附件







错误日志:

11-14 10:12:55.272 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Trying to fetch auth token

11-14 10:12:55.276 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Successfully fetched token, opening connection

11-14 10:12:55.281 27901-27926/com.example.davi.projetofirebase D/Connection: conn_14 - Opening a connection

11-14 10:12:55.293 27901-27926/com.example.davi.projetofirebase D/WebSocket: ws_14 - WebSocket error. bkx: unknown host: s-usc1c-nss-208.firebaseio.com at bku.d(:com.google.android.gms.DynamiteModulesC@11746448:102) at bkv.run(:com.google.android.gms.DynamiteModulesC@11746448:4) at java.lang.Thread.run(Thread.java:760) Caused by: java.net.UnknownHostException: s-usc1c-nss-208.firebaseio.com at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:174) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:356) at java.net.Socket.connect(Socket.java:586) at com.android.org.conscrypt.OpenSSLSocketImpl.connect(OpenSSLSocketImpl.java:265) at com.android.org.conscrypt.OpenSSLSocketImpl.connect(OpenSSLSocketImpl.java:252) at java.net.Socket.(Socket.java:427) at java.net.Socket.(Socket.java:210) at javax.net.ssl.SSLSocket.(SSLSocket.java:906) at com.android.org.conscrypt.OpenSSLSocketImpl.(OpenSSLSocketImpl.java:192) at com.android.org.conscrypt.OpenSSLSocketFactoryImpl.createSocket(OpenSSLSocketFactoryImpl.java:68) at bku.d(:com.google.android.gms.DynamiteModulesC@11746448:94) at bkv.run(:com.google.android.gms.DynamiteModulesC@11746448:4)  at java.lang.Thread.run(Thread.java:760) 

11-14 10:12:55.294 27901-27926/com.example.davi.projetofirebase D/WebSocket: ws_14 - closing itself

11-14 10:12:55.295 27901-27926/com.example.davi.projetofirebase D/Connection: conn_14 - Realtime connection failed

11-14 10:12:55.295 27901-27926/com.example.davi.projetofirebase D/Connection: conn_14 - closing realtime connection

11-14 10:12:55.295 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Got on disconnect due to OTHER

11-14 10:12:55.296 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Scheduling connection attempt

11-14 10:12:55.297 27901-27926/com.example.davi.projetofirebase D/ConnectionRetryHelper: Scheduling retry in 27403ms

11-14 10:12:55.304 27901-27926/com.example.davi.projetofirebase D/WebSocket: ws_14 - closed

11-14 10:13:02.947 27901-27926/com.example.davi.projetofirebase D/PersistentConnection: pc_0 - Connection interrupted for: connection_idle

11-14 10:13:02.960 27901-27926/com.example.davi.projetofirebase D/ConnectionRetryHelper: Cancelling existing retry attempt

Answer 1

我联系了支持团队 Firebase，他们告诉我一个显然解决了我的问题的解决方案:

显然，如果数据库没有 Activity 的操作或监听器，则 .info/connected 的监听器将停止监听。我向数据库中的任何一个节点添加了另一个帮助监听器，并且它起作用了!

DatabaseReference myConnectionRef2 = database.getReference("/users/joe/lastOnline");
myConnectionRef2.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.getValue() == null) {
            System.out.println("FIREBASE: Aux connected");
        } else {
            System.out.println("FIREBASE: Aux not connected");
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

每次我失去网络连接时，两个监听器都会尝试恢复通信，直到网络重新连接。

感谢所有帮助我解决这个问题的人。