Firebase聊天应用程序中的在线用户 [英] Online users in firebase chat app

问题描述

我正在使用Firebase数据库构建一个chatapp。我需要显示在线用户，我该怎么做？
我已经尝试过这个

I am building a chatapp using firebase database. I need to show online users, how can I do that? I already tried this

connectedRef = FirebaseDatabase.getInstance().getReference(".info/connected");
    connectedRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            boolean connected = snapshot.getValue(Boolean.class);
            if (connected) {

            } else {

            }
        }

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

但是我不知道如何使用，请帮帮我。

But I don't know how to use it, please help me.

推荐答案

要实现此目的，您需要在Firebase数据库中创建一个名为 onlineUsers 的新类别。每次用户连接到您的应用程序时，请将其添加到此新创建的类别中。然后，您可以在该类别上查询以查看确切的用户数量，如下所示：

To achieve this, you need to create a new category in your Firebase database called onlineUsers. Every time a user is connecting to your app, add him to this newly created category. Then you can query on that category to see the exact number of users like this:

int numberOfUsers = dataSnapshot.getChildrenCount();.

如果您需要在成员列表中为在线成员显示绿点，则输入方式您需要在这些新节点中添加这些用户的方法是将id作为键，并将值作为布尔值。默认布尔值必须为 false ，这意味着用户尚未登录。新节点应如下所示：

If you need to display a green dot for online members in a list of members, then the way in which you need to add these users in this new node, is to have the id as it's key and the value as a boolean. The default boolean value must be false, which means that the user is not logged in. Your new node should look like this:

userId1: true
userId2: false
userId3: true

每次用户登录时，将该用户的值从 false 更改为 true 。要显示它们，只需相应地查询您的数据库，以查看哪些用户具有 true 的值。

Every time a user signs in, change the value of that user from false to true. To display them, just query your database accordingly to see which users have the value of true.

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