I'm seeing exceptions when ActivityManager.isUserAMonkey() is run on older Android devices:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp.AndroidApp}: java.lang.RuntimeException: Unknown exception code: 1 msg null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2781)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2797)
at android.app.ActivityThread.access$2300(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2132)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:143)
at android.app.ActivityThread.main(ActivityThread.java:4914)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.RuntimeException: Unknown exception code: 1 msg null
at android.os.Parcel.readException(Parcel.java:1257)
at android.os.Parcel.readException(Parcel.java:1235)
at android.app.ActivityManagerProxy.isUserAMonkey(ActivityManagerNative.java:2762)
at android.app.ActivityManager.isUserAMonkey(ActivityManager.java:990)
at <com.myapp....> ...
There is a bit of discussion of the bug here (including a classic thats-not-possible response from one of the developers: "In the standard platform implementation this is pretty much not possible.")
https://groups.google.com/forum/?fromgroups=#!topic/android-developers/tQJcM4O4WxM
Its not clear to me if this always happens, or only happens when running under a test monkey, or only on some devices or what. (I'm running into this problem using Apkudo's device testing service, where the user is always a monkey.) Its not clear when this was fixed, either (it doesn't happen on most (all?) newer devices).
The exception seems to be restricted to Android 2.2 (SDK version 8) releases. And seems to have been a bug in android.app.ActivityManagerNative.
Here's the 2.2.1 code (found in ActivityManagerNative.java on grepcode.com):
1248 case IS_USER_A_MONKEY_TRANSACTION: {
1249 data.enforceInterface(IActivityManager.descriptor);
1250 reply.writeInt(isUserAMonkey() ? 1 : 0);
1251 reply.writeNoException();
1252 return true;
1253 }
Here's the 2.3.1 code (which seems to be the same as much more recent 4.x code which I know works correctly). (Also found on grepcode.com):
1248 case IS_USER_A_MONKEY_TRANSACTION: {
1239 data.enforceInterface(IActivityManager.descriptor);
1240 boolean areThey = isUserAMonkey();
1241 reply.writeNoException();
1242 reply.writeInt(areThey ? 1 : 0);
1243 return true;
1244 }
Notice the order of writeNoException and writeInt are reversed in the newer code. The corresponding code to read the parcel seems to be unchanged since 2.2.1 as far as I can tell:
2749 public boolean isUserAMonkey() throws RemoteException {
2750 Parcel data = Parcel.obtain();
2751 Parcel reply = Parcel.obtain();
2752 data.writeInterfaceToken(IActivityManager.descriptor);
2753 mRemote.transact(IS_USER_A_MONKEY_TRANSACTION, data, reply, 0);
2754 reply.readException();
2755 boolean res = reply.readInt() != 0;
2756 data.recycle();
2757 reply.recycle();
2758 return res;
2759 }
This side reads the exception first, then expects the data.
The javadoc for Parcel readException and writeException imply that they record the exception in the parcel's header (and thus shouldn't impact the actual data in the parcel), but it seems the order does matter.
This means on SDK version 8 the ActivietyManager.isUserAMonkey() API will always throw an exception, monkey or not. Android builds after SDK 8 should not throw this exception.
I suspect the SDK 8 exception message might be slightly different without a monkey ("1 msg null" vs. maybe "0 msg null"?), but don't have an example of the exception without a monkey running.