显示用户离线的最佳方式 - Firebase Android

Question

I am developing an app in which the presence status of the user must be visible to other users. Following this tutorial I built the following code in my first activity

override fun onStart() {
    super.onStart()
    val database = FirebaseDatabase.getInstance()

    val lastOnlineRef = database.getReference("/usuarios/${UsuarioFirebase.getId()}/status")

    val connectedRef = database.getReference(".info/connected")
    connectedRef.addValueEventListener(object : ValueEventListener {
        override fun onDataChange(snapshot: DataSnapshot) {
            val connected = snapshot.getValue(Boolean::class.java) ?: false
            if (connected) {

                lastOnlineRef.setValue("online")

                lastOnlineRef.onDisconnect().setValue(System.currentTimeMillis().toString())

            } else {
                Log.d("ONLINE", "not connected")
            }
        }

        override fun onCancelled(error: DatabaseError) {
            Log.w("ONLINE", "Listener was cancelled at .info/connected")
        }
    })
}

The code works fine when closing the app, saving the time the app was last active. However when opening another app and my app is in the background, firebase shows my user as "online".

Maybe I should indicate that the user is offline in the onPause () method of each actvity, but my app has a lot of actvities. What is the best way to solve this problem?

Answer 1

Best way to handle such a scenario is to use ActivityLifecycleHandler

Below is the example which must be extended by Application Class

Hope it will answer your question

Note: I made this to track start and resume, similarly you can have it for pause state

    private LifecycleListener listener;
    private int started;
    private int resumed;

    public ActivityLifecycleHandler(LifecycleListener listener) {
        this.listener = listener;
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle bundle) {
    }

    @Override
    public void onActivityStarted(Activity activity) {
        if (started == 0 && listener != null) {
            listener.onApplicationStarted();
        }
        started++;
    }

    @Override
    public void onActivityResumed(Activity activity) {
        resumed++;
    }

    @Override
    public void onActivityPaused(Activity activity) {
        resumed--;
    }

    @Override
    public void onActivityStopped(Activity activity) {
        started--;
    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle bundle) {
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
    }

    /**
     * Informs the listener about application lifecycle events.
     */
    public interface LifecycleListener {
        /**
         * Called right before the application is stopped.
         */
        void onApplicationStopped();

        /**
         * Called right after the application has been started.
         */
        void onApplicationStarted();

        /**
         * Called when the application has gone to the background.
         */
        void onApplicationPaused();

        /**
         * Called right after the application has come to the foreground.
         */
        void onApplicationResumed();
    }
}

Answer 2

You can tell firebase to go offline in your onStop method

    FirebaseDatabase.getInstance().goOffline();

Again, go online in your onResume method

    FirebaseDatabase.getInstance().goOnline();