Xamarin.Android: R.java error APT2258 invalid symbol name fix

If you are facing this issue:

R.java : error APT2258: invalid symbol name 'com.companyname.appname:drawable/xxxx'.

You should check for your Resources folder, and look for files with name like a C# or Java keyword. For example: new, public, private, static, class, and so on.

If you rename the file, it will solve your problem.

Xamarin.Android: Missing aapt.exe

When trying to deploy an application to simulator or device, Visual Studio gives the following error:

Cannot find `aapt.exe`. Please install the Android SDK Build-Tools package with the `C:\Program Files (x86)\Android\android-sdk\tools\android.bat` program.

To solve this problem you sould go to Visual Studio’s Tools then Android and select SDK Manager option.

Navigate to this option

It will give an error dialog, that the SDK tool files are corrupted. Click repair.

Click on Repair

The mentioned batch command in the error message is deprecated by the way.

Microsoft Windows [Version 10.0.19042.804]
(c) 2020 Microsoft Corporation. All rights reserved.

C:\Users\banditoth>cd C:\Program Files (x86)\Android\android-sdk\tools\

C:\Program Files (x86)\Android\android-sdk\tools>android.bat
**************************************************************************
The "android" command is deprecated.
For manual SDK, AVD, and project management, please use Android Studio.
For command-line tools, use tools\bin\sdkmanager.bat
and tools\bin\avdmanager.bat
**************************************************************************

Invalid or unsupported command ""

Supported commands are:
android list target
android list avd
android list device
android create avd
android move avd
android delete avd
android list sdk
android update sdk

C:\Program Files (x86)\Android\android-sdk\tools>

Xamarin: Android bindings library could not build

It seems, the new Visual Studio 2019 release with version 16.7 could not build the AndroidBindings projects. (For further information about what is an android binding proj, see: https://docs.microsoft.com/en-us/xamarin/android/platform/binding-java-library/)

The compiler gives the following error message:

...\MSBuild\Xamarin\Android\Xamarin.Android.Bindings.targets(327,5): warning MSB6002: The command-line for the "BindingsGenerator" task is too long. Command-lines longer than 32000 characters are likely to fail. Try reducing the length of the command-line by breaking down the call to "BindingsGenerator" into multiple calls with fewer parameters per call.

Workarounds like: Change the path of the soulution to shorter one does not seems to work.
The only solution for the problem was to downgrade VisualStudio to 16.5.4 (to the last working one for me)

Xamarin Android: “Program type already present”

AndroidX migráció után a következő hibaüzenettel nem fordul le az alkalmazás:

D8 : error : Program type already present: android.support.v4.app.INotificationSideChannel$Stub$Proxy

Próbáltam mindent, kitöröltem a lokális NuGet Cache-t, az összes bin és obj mappát, Cleanelni a Solutiont, Restoreolni a NuGet-eket. Nem járt eredménnyel semmi sem. Aztán nyitottam egy hibát az AndroidX repo-n (https://github.com/xamarin/AndroidX/issues/100) , ahol a megszokotthoz képest lassan reagáltak, akkor sem tudtak érdemben segíteni, így magamnak kellett megoldást találni a problémára.

Elsőre feltelepítettem egy virtuális gépre friss Windows 10-et, rá pedig egy 2019-es Visual Studio Community-t. Lecloneoztam a repositoryt, megfordítottam, és sikeresen lefordult. Itt már gondoltam, hogy valami specifikus hiba lesz. Pár hétre jegelve lett a projekt, majd végül a megoldása az lett, hogy a host gépen teljesen eltávolítottam fizikailag az Azure DevOps GIT alapú repositoryt, majd újra leszedtem a remote-ról, és működött.