ClassNotFoundException when trying to build an existing Xamarin project

Question

I have received an existing Xamarin project that I need to work on before we can release it.

I have tried installing it on 2 different devices:

Nexus 5, running Android 6.0 (API 23)
Emulator Android 4.4 (API 19) - Emulated through Visual Studio Emulator for Android

However, every time I do, it crashes on launch with a java.lang.classNotFoundException: Didn't find class "md515fc9a7f42ec11c09d24b1c1a9770737.ConnectScreen" (full stacktrace below) (ConnectScreen is my MainLauncher)

Things I've tried:

Deleting bin/obj folder and rebuilding
Clean Project and rebuild
Killing MSBuild process, clean and rebuild

After doing some research, I have found Classy-Shark, which allows me to discover the DEX list in a .apk file. From this, it looks like the ConnectScreen is not compiled in the package md515fc9a7f42ec11c09d24b1c1a9770737 (that the app is looking for) but md5bc065f6c935f653292ddf7352d29f8ad. This doesn't seem right to me?

(Those 2 package change every time I build the project)

I have tried to build a new project (Cross-Platform App, Native, Master Details, .NET Standard) and this project worked fine on my Nexus 5, so I don't think it's because of my phone or Visual Studio version?

I have tried changing the MultiDex settings, as well as the TargetFramework, but I still get the same issue.

Here's the full stacktrace:

Unhandled Exception:

Java.Lang.RuntimeException: Unable to instantiate activity ComponentInfo{MyApp.MyApp/md515fc9a7f42ec11c09d24b1c1a9770737.ConnectScreen}: java.lang.ClassNotFoundException: Didn't find class "md515fc9a7f42ec11c09d24b1c1a9770737.ConnectScreen" on path: DexPathList[[zip file "/data/app/MyApp.MyApp-1.apk"],nativeLibraryDirectories=[/data/app-lib/MyApp.MyApp-1, /system/lib]]

12-22 10:39:51.537 E/AndroidRuntime( 1255): FATAL EXCEPTION: main
12-22 10:39:51.537 E/AndroidRuntime( 1255): Process: MyApp.MyApp, PID: 1255
12-22 10:39:51.537 E/AndroidRuntime( 1255): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{MyApp.MyApp/md515fc9a7f42ec11c09d24b1c1a9770737.ConnectScreen}: java.lang.ClassNotFoundException: Didn't find class "md515fc9a7f42ec11c09d24b1c1a9770737.ConnectScreen" on path: DexPathList[[zip file "/data/app/MyApp.MyApp-1.apk"],nativeLibraryDirectories=[/data/app-lib/MyApp.MyApp-1, /system/lib]]
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.os.Handler.dispatchMessage(Handler.java:102)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.os.Looper.loop(Looper.java:136)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.ActivityThread.main(ActivityThread.java:5001)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at java.lang.reflect.Method.invokeNative(Native Method)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at java.lang.reflect.Method.invoke(Method.java:515)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at dalvik.system.NativeStart.main(Native Method)
12-22 10:39:51.537 E/AndroidRuntime( 1255): Caused by: java.lang.ClassNotFoundException: Didn't find class "md515fc9a7f42ec11c09d24b1c1a9770737.ConnectScreen" on path: DexPathList[[zip file "/data/app/MyApp.MyApp-1.apk"],nativeLibraryDirectories=[/data/app-lib/MyApp.MyApp-1, /system/lib]]
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at java.lang.ClassLoader.loadClass(ClassLoader.java:497)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at java.lang.ClassLoader.loadClass(ClassLoader.java:457)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
12-22 10:39:51.537 E/AndroidRuntime( 1255):     ... 11 more
12-22 10:39:53.137 I/Process ( 1255): Sending signal. PID: 1255 SIG: 9

See https://developer.xamarin.com/releases/android/xamarin.android_8/xamarin.android_8.1/#Known_Issues — Jon Douglas, Dec 22 '17 at 19:02
Thank you Jon, that's what I discovered as well after downgrading my version of visual studio. — Mia Lemoine, Jan 02 '18 at 13:33

score 0 · Accepted Answer · answered Dec 22 '17 at 12:46

0

Turns out it seems to be a bug with the latest version of Visual Studio 2017 (15.5).

After downgrading Visual Studio to 15.0, it seems to work fine.

This is only a temporary solution, but I hope it might help other people.

answered Dec 22 '17 at 12:46

Mia Lemoine

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ClassNotFoundException when trying to build an existing Xamarin project

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