Firebase离线数据库数据清除当我重新启动移动设备或此Android/Firebase应用程序？**

Question

我离线使用此代码，并使用Firebase同步Android应用程序中的数据。Firebase离线数据库数据清除当我重新启动移动设备或此Android/Firebase应用程序？

    DatabaseReference scoresRef = FirebaseDatabase.getInstance().getReference("scores");
    scoresRef.keepSynced(true);

    final FirebaseDatabase database = FirebaseDatabase.getInstance();
    final DatabaseReference myConnectionsRef = database.getReference("users/joe/connections");

//存储我最后一次断开连接的时间戳（我最后一次被看到在线）最终数据库参考lastOnlineRef=database.get参考（/用户/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) {

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

                // 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);


            }
        }

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

Answer 1

***********在mFirebaseDatabase之前编写此代码。getReference（）*********

     mFirebaseDatabase = FirebaseDatabase.getInstance();

    // Fire up data persistence to work offline.
    // It's used once in app (not in each activity).
    try {
        mFirebaseDatabase.setPersistenceEnabled(true);
    } catch (DatabaseException e) {
        // Do anything
    }