[Bug] Android APK is 1MB larger after upgrading Xamarin.Forms from SR4 to SR5

[holecekp]

Description

I have upgraded Xamarin.Forms 5.0 to SR5 in my project and I was surprised that the APK file became suddenly almost 1 MB larger.

I have tried also to create a new shell project using the default template in Visual Studio and I can confirm that also for this project the size grows rapidly just by upgrading the Xamarin.Forms Nuget to the latest SR5 version. I have set linker to link everything and enabled r8 to get the smallest APK size possible. I had to add Preserve attributes on a few places to make the project run work without crashing. Here is a comparison of the sizes:

Xamarin.Forms 5.0.0.2083: 17.8 MB
Xamarin.Forms 5.0.0.2125: 18.6 MB

The difference is almost 1 MB for the default project created by Visual Studio (and it is even more for more complex apps). The biggest increase seems to be in the classes.dex file.

What caused this? Is this extra size added by some external dependencies? Or is it a linker problem?

Steps to Reproduce

1. Create an empty shell project using the default Visual Studio template.
2. Archive it.
3. Update Xamarin.Forms Nuget, archive it again and observe the difference of the APKs sizes.

Expected Behavior

All service releases should produce APKs with similar sizes as they does not bring any new features.

Actual Behavior

Upgrading Xamarin.Forms to SR5 increases APK size significantly.

Basic Information

• Version with issue: Xamarin.Forms 5.0 SR5
• Last known good version: Xamarin.Forms 5.0 SR4
• Platform Target Frameworks:
  • Android: 10
• NuGet Packages: Just the default packages from the Visual Studio template

Environment

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Microsoft Visual Studio Community 2019
Version 16.11.5
VisualStudio.16.Release/16.11.5+31729.503
Microsoft .NET Framework
Version 4.8.04084

Installed Version: Community

Visual C++ 2019   00435-60000-00000-AA088
Microsoft Visual C++ 2019

ASP.NET and Web Tools 2019   16.11.75.64347
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ASP.NET Web Frameworks and Tools 2019   16.11.75.64347
For additional information, visit https://www.asp.net/

Azure App Service Tools v3.0.0   16.11.75.64347
Azure App Service Tools v3.0.0

Azure Functions and Web Jobs Tools   16.11.75.64347
Azure Functions and Web Jobs Tools

C# Tools   3.11.0-4.21403.6+ae1fff344d46976624e68ae17164e0607ab68b10
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Common Azure Tools   1.10
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Microsoft Visual Studio VC Package   1.0
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Mono Debugging for Visual Studio   16.10.15 (552afdf)
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NuGet Package Manager   5.11.0
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ProjectServicesPackage Extension   1.0
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VisualStudio.Mac   1.0
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Xamarin   16.11.000.190 (d16-11@2391ed9)
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Xamarin Designer   16.11.0.17 (remotes/origin/11e0001f0b17269345e80b58fb3adf1ba4efe2cd@11e0001f0)
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Xamarin Templates   16.10.5 (355b57a)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK   11.4.0.5 (d16-11/7776c9f)
Xamarin.Android Reference Assemblies and MSBuild support.
    Mono: c633fe9
    Java.Interop: xamarin/java.interop/d16-11@48766c0
    ProGuard: Guardsquare/proguard/v7.0.1@912d149
    SQLite: xamarin/sqlite/3.35.4@85460d3
    Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-11@683f375


Xamarin.iOS and Xamarin.Mac SDK   15.0.0.8 (0796d78dc)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

Workaround

Downgrade Xamarin.Forms to the nearest older version that works for you (this is SR3 in my case, because I had problems with SR4).

[jfversluis]

Probably due to #14101 then, I wouldn't know what else @jonathanpeppers is this something that sounds familiar to you?

[jonathanpeppers]

Can someone share the .apk files of before and after?

If you don't want to actually share the .apk, you can also use this tool: https://www.nuget.org/packages/apkdiff/

> apkdiff -f before.apk after.apk

It prints out the contents of what actually changed.

I would also only compare Release builds you're shipping.

[holecekp]

I have not downloaded akpdiff yet (I will post its output later), but I have used APK analyzer from Android Studio which can also compare the newer version with the old one. The biggest change is in classes.dex. It is a release build with linker and r8 enabled:

[jonathanpeppers]

So if classes.dex increases, that just means there is now more Java code in there.

So are the newer AndroidX classes just larger? Can you share the before/after classes.dex files? I use a tool called dexdump to compare. This looks like a screenshot of Android Studio, I'm not sure if it has a "diff view" between two .apk files.

[holecekp]

I am sending the dex files for both Xamarin.Forms versions:
dex files.zip

I am also including the source for the project. But this is just the default project created by Visual Studio template with updated Nugets and a few settings for smaller size (linker, r8):
EmptyXamarinSizeTest.zip

I have just noticed that when I am upgrading the Nuget to SR5, Visual Studio shows a dialog with changes preview. It lists not not only updates to AndroidX packages but also a few new ones:

Xamarin.AndroidX.Concurrent.Futures
Xamarin.AndroidX.ConstrainedLayout
Xamarin.AndroidX.ConstrainedLayout.Core
Xamarin.AndroidX.DynamicAnimation
Xamarin.AndroidX.Tracing.Tracing

Maybe these are the reason for the size increase. However, 1 MB is quite a lot when a new service release with only bug fixes and no new functionality is installed. So I am wondering if the things added by SR5 are really code that is used or something unused that should be linked out.

[jonathanpeppers]

Yes, there appear to be many more java types:

--class_defs_size     : 2788
++class_defs_size     : 3475

Here is a list of the types, and they just seem to match the newer AndroidX libraries:

• SR4-class-descriptors.txt
• SR5-class-descriptors.txt

You said you are using AndroidLinkTool=r8, is it possible you have some proguard rules that are keeping more classes than they should?

[holecekp]

I have checked that there is no custom proguard rules file. It is a starter project created by Visual Studio template with the following steps:

1. Create a new project of type "Mobile App (Xamarin.Forms)" in Visual Studio 2019
2. One screen of the new project wizard asks which template should be used. I kept the default choice (Flyout) here.
3. I have modified just two settings in the properties for Android project: Code shrinker = r8 and Linking = Sdk and User Assemblies. I had to add Preserve attribute on some places after changing these settings.
4. Finally, I have updated the Nugets.
5. I have built the release version, checked it in the emulator, and archived it into APK.

[jonathanpeppers]

I think the newer AndroidX libraries are just larger. What is the size difference when you turn off r8? Are we sure it's actually shrinking things?

[holecekp]

I checked that R8 is doing something. When I turn it off, the APK is 756 kB larger (19,3 MB in total).