Commits on Dec 16, 2021

1. [android] stop using Build.VERSION.SdkInt …

   We have a beautiful .NET 6 API we can use instead, that doesn't call
   into Java (no JNI!):
   
   https://docs.microsoft.com/dotnet/api/system.operatingsystem.isandroidversionatleast
   
   Usage of `Build.VERSION.SdkInt` came from both Xamarin.Forms and
   Xamarin.Essentials. We were caching the result of the value, but still
   doing that work twice.
   
   We can also use the pattern:
   
       OperatingSystem.IsAndroidVersionAtLeast((int)BuildVersionCodes.JellyBean)
   
   `BuildVersionCodes` is a regular C# enum, and so the C# compiler will
   strip this information away leaving just an integer in the final IL.
   
   I used either an integer or the enum, depending on what the existing
   code did.
   
   Additionally, I went through any existing code checking old API levels and removed it.
   The minimum API level for .NET 6 (dotnet/runtime & xamarin-android) is 21. So any
   code looking for API levels 21 or lower, could just be removed.
   
   I also removed code I found such as:
   
       public static int? TargetSdkVersion(this Context self)
       {
           return (int?)self?.ApplicationInfo?.TargetSdkVersion;
       }
   
   This was only used in one place, and was checking API 17, so I just
   removed it.
   
   ~~ Results ~~
   
   Testing a `Release` build of `Maui.Controls.Sample.SingleProject.csproj`
   on a Pixel 5 device:
   
       Before:
       12-16 14:41:19.289  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s739ms
       12-16 14:41:24.468  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s713ms
       12-16 14:41:29.867  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s917ms
       12-16 14:41:34.905  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s765ms
       12-16 14:41:40.132  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s719ms
       12-16 14:41:45.431  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s768ms
       12-16 14:41:50.608  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s716ms
       12-16 14:41:55.878  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s754ms
       12-16 14:42:01.157  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s754ms
       12-16 14:42:06.315  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s713ms
       Average(ms): 1755.8
       Std Err(ms): 19.1803139819046
       Std Dev(ms): 60.6534784199921
   
       After:
       12-16 14:45:35.208  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s737ms
       12-16 14:45:40.448  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s743ms
       12-16 14:45:45.663  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s715ms
       12-16 14:45:50.931  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s741ms
       12-16 14:45:56.161  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s712ms
       12-16 14:46:01.426  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s768ms
       12-16 14:46:06.574  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s699ms
       12-16 14:46:11.867  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s779ms
       12-16 14:46:16.979  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s694ms
       12-16 14:46:22.229  1741  1935 I ActivityTaskManager: Displayed com.microsoft.maui.sample/crc64dac46b470c4e9200.MainActivity: +1s728ms
       Average(ms): 1731.6
       Std Err(ms): 8.79924239163047
       Std Dev(ms): 27.8256476414596
   
   This appears to maybe save ~24ms on startup for this app?

   

   jonathanpeppers committed Dec 16, 2021
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