NullReferenceException when building Xamarin Android Binding Library

Vladislav 1

I've been trying to build a Xamarin Android Binding Library having a .jar file in it.
It builds just as expected with different .jar-s I tried, however when I add jackson-databind library, I keep receiving

BINDINGSGENERATOR : error BG0000: System.NullReferenceException: Object reference not set to an instance of an object.

C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Xamarin\Android\Xamarin.Android.Bindings.Core.targets(53,5): message BG0000: error BG0000: System.NullReferenceException: Object reference not set to an instance of an object.

I have tried changing between Java 8 and Java 17, changing between Android SDK version. Nothing helps.

Any ideas where to look at next?
Thank you.

Vladislav 1 Reputation point

2021-10-07T14:33:03.807+00:00

The project itself is here:
https://github.com/vladbudnikov/demo-of-NullReferenceException-when-building-Xamarin-Android-Binding-
Library
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 32,386 Reputation points Microsoft Vendor

2021-10-08T05:47:24.007+00:00

This error means you are trying to access an object without instantiating it, I'm not clear about which object is accessed. You could check if there is a class missing.
Vladislav 1 Reputation point

2021-10-08T06:14:37.607+00:00

That's for sure. However, the build output does not give any information on which class is being attempted to be accessed.

Moreover, when I run this library in Android Studio, it builds and works with no issue.

Unfortunately, I cannot paste the build output log her, as it is 10 times longer that is allowed to be typed,
so the log can be seen here:

https://pastebin.pl/view/5b75b9ff
Vladislav 1 Reputation point

2021-10-08T06:18:23.537+00:00

That's for sure. However, the build log does not give any hint on what object is being attempted to be accessed.

Moreover, when I use the same library in Android Studio, it builds and runs with no issue.

The log is too long so I pasted it here:

https://pastebin.pl/view/5b75b9ff
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 32,386 Reputation points Microsoft Vendor

2021-10-11T06:26:34.213+00:00

OK, I got it. I will test again.
Ian 1 Reputation point

2022-04-28T22:29:41.37+00:00

Was this ever resolved? I'm experiencing the same issue binding to an aar library in my project.
Rob Caplan - MSFT 5,537 Reputation points Microsoft Employee

2022-04-28T22:50:00.71+00:00

Hi Ian! Unless you're using the same libraries Vladislav was it is unlikely you're running into the same issue. If you need help please post a new thread with specific details of your scenario.
Zachary Buresh 0 Reputation points

2024-07-26T19:52:05.7166667+00:00

I'm also experiencing the same issue with the com.fasterxml.jackson.core:jackson-databind:2.17.1 library. It doesn't tell me any details about what is null or where it occurs.
Lewis Spencer 0 Reputation points

2024-09-18T12:04:14.61+00:00

I was getting this issue when migrating a xamarin project to a .NET Maui project.

I named the recently migrated project x.x.MAUI and added it as a project reference to another project. I later changed the name of the project to x.x.Maui and on my next build, I received this error.

To fix this, I manually updated the .csproj for the project it is a reference in. The reference was assigned as: x.x.MAUI\x.x.Maui.csproj. When updating the name, only the project name had been updated not the folder, causing this error. I also then updated the folder name in my src folder.

I had a look at your solution in github and can't see this occurring there, but thought I would leave this comment in case someone encounters this issue instead.

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NullReferenceException when building Xamarin Android Binding Library

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