Can there be multiple instances of a dependency in Xamarin.Forms? - xamarin.forms

Question

I have mirrored some code from XLabs to get Network State Tracking on my device from here: Xlabs INetwork Android Implementation
I've pretty much aligned it with coding standards here and changed some method names - everything is working fine, except for some reason on the android implementation i am unable to get my event handlers to respond, the same way they do on iOS.
This is my Adaptation for Android:
[assembly: Dependency(typeof(STM.Droid.DependencyInjection.Network))]
[assembly: UsesPermission("android.permission.ACCESS_NETWORK_STATE")]
[assembly: UsesPermission("android.permission.ACCESS_WIFI_STATE")]
[assembly: UsesPermission("android.permission.CHANGE_NETWORK_STATE")]
[assembly: UsesPermission("android.permission.CHANGE_WIFI_STATE")]
namespace Namespace.Droid
{
[BroadcastReceiver(Enabled = true)]
[IntentFilter(new [] { Android.Net.ConnectivityManager.ConnectivityAction })]
public class Network : BroadcastReceiver, INetwork
{
/// <summary>
/// Internets the connection status.
/// </summary>
/// <returns>NetworkStatus.</returns>
public NetworkStatus GetConnectionStatus()
{
var status = NetworkStatus.NotReachable;
using (var cm = (ConnectivityManager)Application.Context.GetSystemService(Context.ConnectivityService))
using (var ni = cm.ActiveNetworkInfo)
{
if (ni != null && ni.IsConnectedOrConnecting)
{
var name = ni.TypeName.ToUpper();
if (name.Contains("WIFI"))
{
status = NetworkStatus.ReachableViaWiFiNetwork;
}
else if (name.Contains("MOBILE"))
{
status = NetworkStatus.ReachableViaCarrierDataNetwork;
}
else
{
status = NetworkStatus.ReachableViaUnknownNetwork;
}
}
}
return status;
}
private readonly object lockObject = new object();
private EventHandler<NetworkStatus> _reachabilityChanged;
public event EventHandler<NetworkStatus> ReachabilityChanged
{
add
{
lock (this.lockObject)
{
this._reachabilityChanged += value;
}
}
remove
{
lock (this.lockObject)
{
this._reachabilityChanged -= value;
}
}
}
/// <summary>
/// Occurs when [reachability changed].
/// </summary>
// public event EventHandler<NetworkStatus> ReachabilityChanged;
/// <summary>
/// Determines whether the specified host is reachable.
/// </summary>
/// <param name="host">The host.</param>
/// <param name="timeout">The timeout.</param>
public Task<bool> IsReachableAsync(string host, TimeSpan timeout)
{
return Task.Run(
() =>
{
try
{
var address = InetAddress.GetByName(host);
return address != null; // && (address.IsReachable((int)timeout.TotalMilliseconds) || );
}
catch (UnknownHostException)
{
return false;
}
});
}
/// <summary>
/// Determines whether [is reachable by wifi] [the specified host].
/// </summary>
/// <param name="host">The host.</param>
/// <param name="timeout">The timeout.</param>
public async Task<bool> IsReachableByWifiAsync(string host, TimeSpan timeout)
{
return GetConnectionStatus() == NetworkStatus.ReachableViaWiFiNetwork && await IsReachableAsync(host, timeout);
}
/// <summary>
/// This gets called by OS when the <see cref="ConnectivityManager.ConnectivityAction"/> <see cref="Intent"/> fires.
/// </summary>
/// <param name="context">Context for the intent.</param>
/// <param name="intent">Intent information.</param>
public override void OnReceive(Context context, Intent intent)
{
// this is a workaround - which oddly enough forwards events the way i would expect it to.
MessagingCenter.Send(this as INetwork, string.Empty, GetConnectionStatus());
// THIS IS ALWAYS NULL!
var handler = _reachabilityChanged;
if (handler != null)
{
var connectionStatus = this.GetConnectionStatus();
handler(this, connectionStatus);
}
}
}
}
The error in question occurs in OnReceive.
While in debugging i do notice that the handlers are attached correctly on the PCL side - there will just be null on that _reachabilityChanged field oddly enough.
As debugging indicates i am apparently getting
{md50e2cce2f1202796e628729fe0540389b.Network#b422684}
on the droid OnReceive method for "this"
while on the PCL side i am getting
{md50e2cce2f1202796e628729fe0540389b.Network#b562641}
when calling DependencyService.Get
To me this looks like the reason the handler list is empty, is because i am subscribing my handler on another instance and therefore do not get any handlers when a different instance of Network calls OnReceive.
Is it even possible for Xamarin.Forms DependencyService to provide 2 or more instances of an instance? Because that would surprise me a lot...
UPDATE:
In case someone needs a workaround - this works as well:
public event EventHandler<NetworkStatus> ReachabilityChanged
{
add { MessagingCenter.Subscribe(value.Target, string.Empty, (INetwork d, NetworkStatus a) => value(d, a)); }
remove { MessagingCenter.Unsubscribe<INetwork>(value.Target, string.Empty); }
}

Answer 1

for new instance
_client = DependencyService.Get<YOUINTERFACE>(DependencyFetchTarget.NewInstance);
by default DependencyService is keep single