From b9a2f76cf0bcbb49e9bab5a50f00de8789c2e9e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Pedro?= <jpedrolmail@gmail.com>
Date: Wed, 10 Feb 2021 23:58:51 +0000
Subject: [PATCH] Added timer subscriptions for views.

---
 src/Android/Avalonia.Android/AvaloniaView.cs  |  8 +++++
 .../Avalonia.Android/ChoreographerTimer.cs    | 29 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/src/Android/Avalonia.Android/AvaloniaView.cs b/src/Android/Avalonia.Android/AvaloniaView.cs
index a60a17d08e..8de3657283 100644
--- a/src/Android/Avalonia.Android/AvaloniaView.cs
+++ b/src/Android/Avalonia.Android/AvaloniaView.cs
@@ -15,6 +15,8 @@ namespace Avalonia.Android
         private readonly EmbeddableControlRoot _root;
         private readonly ViewImpl _view;
 
+        private IDisposable? _timerSubscription;
+
         public AvaloniaView(Context context) : base(context)
         {
             _view = new ViewImpl(context);
@@ -50,11 +52,17 @@ namespace Avalonia.Android
         {
             if (isVisible)
             {
+                if (AvaloniaLocator.Current.GetService<IRenderTimer>() is ChoreographerTimer timer)
+                {
+                    _timerSubscription = timer.SubscribeView(this);
+                }
+
                 _root.Renderer.Start();
             }
             else
             {
                 _root.Renderer.Stop();
+                _timerSubscription?.Dispose();
             }
         }
 
diff --git a/src/Android/Avalonia.Android/ChoreographerTimer.cs b/src/Android/Avalonia.Android/ChoreographerTimer.cs
index 12961fec83..1d898261a3 100644
--- a/src/Android/Avalonia.Android/ChoreographerTimer.cs
+++ b/src/Android/Avalonia.Android/ChoreographerTimer.cs
@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Reactive.Disposables;
 using System.Threading.Tasks;
 
 using Android.OS;
@@ -17,6 +19,8 @@ namespace Avalonia.Android
         private readonly Thread _thread;
         private readonly TaskCompletionSource<Choreographer> _choreographer = new TaskCompletionSource<Choreographer>();
 
+        private readonly ISet<AvaloniaView> _views = new HashSet<AvaloniaView>();
+
         private Action<TimeSpan> _tick;
         private int _count;
 
@@ -51,6 +55,29 @@ namespace Avalonia.Android
             }
         }
 
+        internal IDisposable SubscribeView(AvaloniaView view)
+        {
+            lock (_lock)
+            {
+                _views.Add(view);
+
+                if (_views.Count == 1)
+                {
+                    _choreographer.Task.Result.PostFrameCallback(this);
+                }
+            }
+
+            return Disposable.Create(
+                () =>
+                {
+                    lock (_lock)
+                    {
+                        _views.Remove(view);
+                    }
+                }
+            );
+        }
+
         private void Loop()
         {
             Looper.Prepare();
@@ -64,7 +91,7 @@ namespace Avalonia.Android
 
             lock (_lock)
             {
-                if (_count > 0)
+                if (_count > 0 && _views.Count > 0)
                 {
                     Choreographer.Instance.PostFrameCallback(this);
                 }