Using Firebase for user presence tracking using xamarin forms - xamarin.forms

Question

I am using firebase to track my device on my app. When network is disconnected on my device, I want to notify on the firebase. Based on the below link,
https://firebase.google.com/docs/database/android/offline-capabilities
I am using the following code:
#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 Class:
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);
}
}
}
But it is working only if online only. Can anyone help me to resolve this issue.

Answer 1

In my xaml.cs file:
#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
In Constants.cs file:
public static bool IsFCMOffline = true;
public static DatabaseReference connectedRef;
public static DatabaseReference myConnectionsRef;
In Droid/ValueEventListener.cs file:
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");
}
}
}
In iOS/AppDelegate.cs file:
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)
{
}
}