Android runtime exception - Cannot create instance of type '': no Java peer type found.

[ConnorJBrown]

Android framework version

net10.0-android

Affected platform version

VS 2026 18.7.3, NET 10.0.301, .NET Android 36.1.69

Description

With the Android workload 36.1.69 (which includes the #11208 / #11248 fixes), FindJavaObjectsStep still emits an empty .jlo.xml for a binding assembly when:

1. an Android Java.Lang.Object-derived type has its base class in a second multi-TFM assembly, and
2. a net-only (non-Android) project reference drags a non-Android copy of that second assembly onto the build's assembly search path.

The resolver name-binds the base type to the non-Android copy (where the type isn't compiled in — it's #if ANDROID), fails to recognize the derived type as a Java type, produces <api />, generates no Java Callable Wrapper, and the app throws at launch:

System.NotSupportedException: Cannot create instance of type
'MultiTfmClassLibrary1.AndroidDerivedObject': no Java peer type found.

#11208 loads the primary scanned assembly by path, but does not stop name-based base-type resolution from binding to the stray non-Android copy.

This issue does not happen in .NET 9, and is making it difficult for us to migrate to .NET 10.

Repro project: NoJavaPeerTypeFound.zip

Steps to Reproduce

I attached a solution with this structure:

AndroidApp (net10.0-android)
 ├── direct ─────────────► MultiTfmClassLibrary1 (net10.0;net10.0-android)
 │                             └── AndroidDerivedObject : MultiTfmClassLibrary2.AndroidObject   (#if ANDROID)
 ├── direct ─────────────► MultiTfmClassLibrary2 (net10.0;net10.0-android)
 │                             └── AndroidObject : Java.Lang.Object                             (#if ANDROID)
 └──► ClassLibrary (net10.0 ONLY) ──► MultiTfmClassLibrary1   ← the poison:
                                                                its net10.0 output copies
                                                                non-Android MultiTfmClassLibrary1.dll
                                                                + MultiTfmClassLibrary2.dll onto
                                                                the search path

MainActivity.OnCreate:

var obj = new MultiTfmClassLibrary1.AndroidDerivedObject(); // throws at launch

Did you find any workaround?

Add the Android TFM to every net-only library that (transitively) references an Android-bearing binding assembly:

<TargetFrameworks>net10.0;net10.0-android</TargetFrameworks>

Or downgrade to .NET 9.

Relevant log output

07-07 14:30:39.448 E/AndroidRuntime( 6407): FATAL EXCEPTION: main
07-07 14:30:39.448 E/AndroidRuntime( 6407): Process: com.companyname.AndroidApp, PID: 6407
07-07 14:30:39.448 E/AndroidRuntime( 6407): android.runtime.JavaProxyThrowable: [System.NotSupportedException]: Cannot create instance of type 'MultiTfmClassLibrary1.AndroidDerivedObject': no Java peer type found.
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at Java.Interop.JniPeerMembers+JniInstanceMethods..ctor + 0x3b(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at Java.Interop.JniPeerMembers+JniInstanceMethods.GetConstructorsForType + 0x41(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance + 0x25(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at Java.Lang.Object..ctor + 0x1a(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at MultiTfmClassLibrary2.AndroidObject..ctor(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at MultiTfmClassLibrary1.AndroidDerivedObject..ctor(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at AndroidApp.MainActivity.OnCreate(C:\Users\connor.brown\Documents\Projects\NoJavaPeerTypeFound\NoJavaPeerTypeFound\AndroidApp\MainActivity.cs:15)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ + 0xe(Unknown Source)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at crc64e75cd28e16296800.MainActivity.n_onCreate(Native Method)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at crc64e75cd28e16296800.MainActivity.onCreate(MainActivity.java:28)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.Activity.performCreate(Activity.java:9155)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.Activity.performCreate(Activity.java:9133)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1524)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4265)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4470)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:222)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:133)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:103)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:80)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2826)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.os.Handler.dispatchMessage(Handler.java:110)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.os.Looper.loopOnce(Looper.java:248)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.os.Looper.loop(Looper.java:338)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at android.app.ActivityThread.main(ActivityThread.java:9137)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at java.lang.reflect.Method.invoke(Native Method)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:593)
07-07 14:30:39.448 E/AndroidRuntime( 6407): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:940)