使用Firebase使用xamarin表单进行用户在线跟踪

Posted 2023-01-17

我正在使用firebase在我的应用上跟踪我的设备。当我的设备断开网络连接时，我想在firebase上通知。根据以下链接，https://firebase.google.com/docs/database/android/offline-capabilities我使用以下代码：

#if __android__
FirebaseDatabase firebase = FirebaseDatabase.Instance;
FirebaseDatabase.Instance.SetPersistenceEnabled(true);
                var userListRef = firebase.GetReference("USERS_ONLINE");
                var myUserRef = userListRef.Push();
                DatabaseReference connectedRef = firebase.GetReference(".info/connected");

                connectedRef.AddValueEventListener(new ValueEventListener());

ValueEventListener类：

internal class ValueEventListener : Java.Lang.Object, IValueEventListener
    
       // public IntPtr Handle => throw new NotImplementedException();

        public void Dispose()
        
            throw new NotImplementedException();
        

        public void OnCancelled(DatabaseError error)
        
            throw new NotImplementedException();
        

        public void OnDataChange(DataSnapshot snapshot)
        
            FirebaseDatabase firebase = FirebaseDatabase.Instance;
            DatabaseReference myConnectionsRef = firebase.GetReference("users/joe/connections");
                        bool connected =  Convert.ToBoolean(snapshot.GetValue(true));
            myConnectionsRef.KeepSynced(true);

            if (connected)
            
                DatabaseReference con = myConnectionsRef.Push();
                con.OnDisconnect().RemoveValue();
                myConnectionsRef.SetValue(Boolean.TrueString);
            
            else
            
                DatabaseReference con = myConnectionsRef.Push();
                con.OnDisconnect().RemoveValue();
                myConnectionsRef.SetValue(Boolean.FalseString);
            
        
    

但它只在网上工作。任何人都可以帮我解决这个问题。

答案

在我的xaml.cs文件中：

#if __ANDROID__
                string myConnectionsRefNode = "users/Truckers/Joe/connections";
                Constants.connectedRef = FirebaseDatabase.Instance.GetReference(".info/connected");
                Constants.myConnectionsRef = FirebaseDatabase.Instance.GetReference(myConnectionsRefNode);
                Constants.connectedRef.AddValueEventListener(new MyProject.Droid.Services.ValueEventListener());

#elif __ios__
                var context = AppDelegate.Instance;
                if(context!=null)
        
                    context.FCMOfflineAccess();
                
#endif

在Constants.cs文件中：

public static bool IsFCMOffline = true;
public static DatabaseReference connectedRef;
public static DatabaseReference myConnectionsRef;

在Droid / ValueEventListener.cs文件中：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Firebase.Database;
using MyProject.Common;
namespace MyProject.Droid.Services

    public class ValueEventListener : Java.Lang.Object, IValueEventListener
    
        public void OnCancelled(DatabaseError error)
        
            throw new NotImplementedException();
        

        public void OnDataChange(DataSnapshot snapshot)
        
            DatabaseReference con = Constants.myConnectionsRef.Ref;
            con.OnDisconnect().SetValue("Offline");
            con.SetValue("Online");
        
    

在iOS / AppDelegate.cs文件中：

public void FCMOfflineAccess()
        
                var connectedRef = Database.DefaultInstance;
                var MyConnectedRef = connectedRef.GetReferenceFromPath("users/Truckers/" + TruckerId);
                var connectedRef1 = connectedRef.GetReferenceFromPath(".info/connected");
                connectedRef1.ObserveEvent(DataEventType.Value, HandleAction);
        

        private void HandleAction(DataSnapshot snapshot)
        
            try
            
                var connectedRef = Database.DefaultInstance;
                var con = connectedRef.GetReferenceFromPath("users/Truckers/Joe");

                string[] statOffline =  "Offline" ;
                string[] keyOffline =  "connections" ;
                var dataOffline = NSDictionary.FromObjectsAndKeys(statOffline, keyOffline, keyOffline.Length);
                con.SetValueOnDisconnect(dataOffline);

                string[] statOnline =  "Online" ;
                string[] keyOnline =  "connections" ;
                var dataOnline = NSDictionary.FromObjectsAndKeys(statOnline, keyOnline, keyOnline.Length);
                con.SetValue(dataOnline);

            
            catch (Exception ex)