From 0175072fb6730ebdbbc75cf931be07607bf02796 Mon Sep 17 00:00:00 2001
From: James Montemagno <james.montemagno@gmail.com>
Date: Thu, 3 Dec 2020 11:01:00 -0800
Subject: [PATCH] Implement the new ConnectivityManager.NetworkCallback for N+

---
 .../Connectivity/Connectivity.android.cs      | 74 ++++++++++++++++++-
 .../Platform/Platform.android.cs              |  2 +
 2 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/Xamarin.Essentials/Connectivity/Connectivity.android.cs b/Xamarin.Essentials/Connectivity/Connectivity.android.cs
index 40909ea86..21123f6c2 100644
--- a/Xamarin.Essentials/Connectivity/Connectivity.android.cs
+++ b/Xamarin.Essentials/Connectivity/Connectivity.android.cs
@@ -11,22 +11,46 @@ namespace Xamarin.Essentials
     public partial class Connectivity
     {
         static ConnectivityBroadcastReceiver conectivityReceiver;
+        static Intent connectivityIntent = new Intent(Platform.EssentialsConnectivityChanged);
+        static EssentialsNetworkCallback networkCallback;
 
         static void StartListeners()
         {
             Permissions.EnsureDeclared<Permissions.NetworkState>();
 
-            conectivityReceiver = new ConnectivityBroadcastReceiver(OnConnectivityChanged);
+            var filter = new IntentFilter();
 
+            if (Platform.HasApiLevelN)
+            {
+                RegisterNetworkCallback();
+                filter.AddAction(Platform.EssentialsConnectivityChanged);
+            }
+            else
+            {
 #pragma warning disable CS0618 // Type or member is obsolete
-            Platform.AppContext.RegisterReceiver(conectivityReceiver, new IntentFilter(ConnectivityManager.ConnectivityAction));
+                filter.AddAction(ConnectivityManager.ConnectivityAction);
 #pragma warning restore CS0618 // Type or member is obsolete
+            }
+
+            conectivityReceiver = new ConnectivityBroadcastReceiver(OnConnectivityChanged);
+
+            Platform.AppContext.RegisterReceiver(conectivityReceiver, filter);
         }
 
         static void StopListeners()
         {
             if (conectivityReceiver == null)
                 return;
+
+            try
+            {
+                UnregisterNetworkCallback();
+            }
+            catch
+            {
+                Debug.WriteLine("Connectivity receiver already unregistered. Disposing of it.");
+            }
+
             try
             {
                 Platform.AppContext.UnregisterReceiver(conectivityReceiver);
@@ -39,6 +63,50 @@ static void StopListeners()
             conectivityReceiver = null;
         }
 
+        static void RegisterNetworkCallback()
+        {
+            if (!Platform.HasApiLevelN)
+                return;
+
+            var manager = Platform.ConnectivityManager;
+            if (manager == null)
+                return;
+
+            var request = new NetworkRequest.Builder().Build();
+            networkCallback = new EssentialsNetworkCallback();
+            manager.RegisterNetworkCallback(request, networkCallback);
+        }
+
+        static void UnregisterNetworkCallback()
+        {
+            if (!Platform.HasApiLevelN)
+                return;
+
+            var manager = Platform.ConnectivityManager;
+            if (manager == null || networkCallback == null)
+                return;
+
+            manager.UnregisterNetworkCallback(networkCallback);
+
+            networkCallback?.Dispose();
+            networkCallback = null;
+        }
+
+        class EssentialsNetworkCallback : ConnectivityManager.NetworkCallback
+        {
+            public override void OnAvailable(Network network) => Platform.AppContext.SendBroadcast(connectivityIntent);
+
+            public override void OnLost(Network network) => Platform.AppContext.SendBroadcast(connectivityIntent);
+
+            public override void OnCapabilitiesChanged(Network network, NetworkCapabilities networkCapabilities) => Platform.AppContext.SendBroadcast(connectivityIntent);
+
+            public override void OnUnavailable() => Platform.AppContext.SendBroadcast(connectivityIntent);
+
+            public override void OnLinkPropertiesChanged(Network network, LinkProperties linkProperties) => Platform.AppContext.SendBroadcast(connectivityIntent);
+
+            public override void OnLosing(Network network, int maxMsToLive) => Platform.AppContext.SendBroadcast(connectivityIntent);
+        }
+
         static NetworkAccess IsBetterAccess(NetworkAccess currentAccess, NetworkAccess newAccess) =>
             newAccess > currentAccess ? newAccess : currentAccess;
 
@@ -245,7 +313,7 @@ public ConnectivityBroadcastReceiver(Action onChanged) =>
         public override async void OnReceive(Context context, Intent intent)
         {
 #pragma warning disable CS0618 // Type or member is obsolete
-            if (intent.Action != ConnectivityManager.ConnectivityAction)
+            if (intent.Action != ConnectivityManager.ConnectivityAction && intent.Action != Platform.EssentialsConnectivityChanged)
 #pragma warning restore CS0618 // Type or member is obsolete
                 return;
 
diff --git a/Xamarin.Essentials/Platform/Platform.android.cs b/Xamarin.Essentials/Platform/Platform.android.cs
index 12ea7e397..074da7c72 100644
--- a/Xamarin.Essentials/Platform/Platform.android.cs
+++ b/Xamarin.Essentials/Platform/Platform.android.cs
@@ -27,6 +27,8 @@ public static partial class Platform
 
         public static event EventHandler<ActivityStateChangedEventArgs> ActivityStateChanged;
 
+        internal const string EssentialsConnectivityChanged = "com.xamarin.essentials.ESSENTIALS_CONNECTIVITY_CHANGED";
+
         internal const int requestCodeFilePicker = 11001;
         internal const int requestCodeMediaPicker = 11002;
         internal const int requestCodeMediaCapture = 11003;