From 8100cd3571ad4700d324dbeb393b69d6b450c9de Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sat, 6 Aug 2022 21:39:59 -0400
Subject: [PATCH 1/2] Optimize CurrentThreadIsLoopThread on android backend

---
 .../AndroidThreadingInterface.cs                | 17 ++++++++++++++++-
 .../Avalonia.Android/Avalonia.Android.csproj    |  2 +-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/Android/Avalonia.Android/AndroidThreadingInterface.cs b/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
index e72f0aed90..abc7947f38 100644
--- a/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
+++ b/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
@@ -14,6 +14,7 @@ namespace Avalonia.Android
     internal sealed class AndroidThreadingInterface : IPlatformThreadingInterface
     {
         private Handler _handler;
+        private static Thread s_uiThread;
 
         public AndroidThreadingInterface()
         {
@@ -76,7 +77,21 @@ namespace Avalonia.Android
             EnsureInvokeOnMainThread(() => Signaled?.Invoke(null));
         }
 
-        public bool CurrentThreadIsLoopThread => Looper.MainLooper.Thread.Equals(Java.Lang.Thread.CurrentThread());
+        public bool CurrentThreadIsLoopThread
+        {
+            get
+            {
+                if (s_uiThread != null)
+                    return s_uiThread == Thread.CurrentThread;
+
+                if (Looper.MainLooper.IsCurrentThread)
+                {
+                    s_uiThread = Thread.CurrentThread;
+                    return true;
+                }
+                return false;
+            }
+        }
         public event Action<DispatcherPriority?> Signaled;
     }
 }
diff --git a/src/Android/Avalonia.Android/Avalonia.Android.csproj b/src/Android/Avalonia.Android/Avalonia.Android.csproj
index 6688dde8f5..082ba1f647 100644
--- a/src/Android/Avalonia.Android/Avalonia.Android.csproj
+++ b/src/Android/Avalonia.Android/Avalonia.Android.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>net6.0-android</TargetFramework>
-    <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion>23</SupportedOSPlatformVersion>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <MSBuildEnableWorkloadResolver>true</MSBuildEnableWorkloadResolver>
     <DebugType>portable</DebugType>

From 0e733c70a16e8e465f2691800aed1a350c9fdf47 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sat, 6 Aug 2022 22:48:59 -0400
Subject: [PATCH 2/2] Support 21 api

---
 src/Android/Avalonia.Android/AndroidThreadingInterface.cs | 6 +++++-
 src/Android/Avalonia.Android/Avalonia.Android.csproj      | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/Android/Avalonia.Android/AndroidThreadingInterface.cs b/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
index abc7947f38..42f75a27e1 100644
--- a/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
+++ b/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
@@ -84,11 +84,15 @@ namespace Avalonia.Android
                 if (s_uiThread != null)
                     return s_uiThread == Thread.CurrentThread;
 
-                if (Looper.MainLooper.IsCurrentThread)
+                var isOnMainThread = OperatingSystem.IsAndroidVersionAtLeast(23)
+                    ? Looper.MainLooper.IsCurrentThread
+                    : Looper.MainLooper.Thread.Equals(Java.Lang.Thread.CurrentThread());
+                if (isOnMainThread)
                 {
                     s_uiThread = Thread.CurrentThread;
                     return true;
                 }
+
                 return false;
             }
         }
diff --git a/src/Android/Avalonia.Android/Avalonia.Android.csproj b/src/Android/Avalonia.Android/Avalonia.Android.csproj
index 082ba1f647..6688dde8f5 100644
--- a/src/Android/Avalonia.Android/Avalonia.Android.csproj
+++ b/src/Android/Avalonia.Android/Avalonia.Android.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>net6.0-android</TargetFramework>
-    <SupportedOSPlatformVersion>23</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <MSBuildEnableWorkloadResolver>true</MSBuildEnableWorkloadResolver>
     <DebugType>portable</DebugType>