Android release APK crash with java.lang.AssertionError: impossible in java.lang.Enum

Question

I've just built an APK using Gradle for release (ProGuard 4.9 and signed). When I launch the app it crash on this error :

E/AndroidRuntime( 8662): java.lang.AssertionError: impossible
E/AndroidRuntime( 8662):    at java.lang.Enum$1.create(Enum.java:44)
E/AndroidRuntime( 8662):    at java.lang.Enum$1.create(Enum.java:35)
E/AndroidRuntime( 8662):    at libcore.util.BasicLruCache.get(BasicLruCache.java:54)
E/AndroidRuntime( 8662):    at java.lang.Enum.getSharedConstants(Enum.java:210)
E/AndroidRuntime( 8662):    at java.lang.Enum.valueOf(Enum.java:190)
E/AndroidRuntime( 8662):    at kr.infli.s.Z(Inflikr.java:390)
E/AndroidRuntime( 8662):    at kr.infli.a.ev(Inflikr.java:409)
E/AndroidRuntime( 8662):    at kr.infli.activity.InflikrActivity.onResume(InflikrActivity.java:231)
E/AndroidRuntime( 8662):    at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1192)
E/AndroidRuntime( 8662):    at android.app.Activity.performResume(Activity.java:5310)
E/AndroidRuntime( 8662):    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2778)
E/AndroidRuntime( 8662):    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2817)
E/AndroidRuntime( 8662):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
E/AndroidRuntime( 8662):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
E/AndroidRuntime( 8662):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
E/AndroidRuntime( 8662):    at android.os.Handler.dispatchMessage(Handler.java:102)
E/AndroidRuntime( 8662):    at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime( 8662):    at android.app.ActivityThread.main(ActivityThread.java:5017)
E/AndroidRuntime( 8662):    at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime( 8662):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
E/AndroidRuntime( 8662):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
E/AndroidRuntime( 8662): Caused by: java.lang.NoSuchMethodException: values []
E/AndroidRuntime( 8662):    at java.lang.Class.getMethod(Class.java:661)
E/AndroidRuntime( 8662):    at java.lang.Class.getDeclaredMethod(Class.java:623)
E/AndroidRuntime( 8662):    at java.lang.Enum$1.create(Enum.java:41)
E/AndroidRuntime( 8662):    ... 20 more

Looks like this error should not happen : https://android.googlesource.com/platform/libcore/+/9edf43dfcc35c761d97eb9156ac4254152ddbc55/libdvm/src/main/java/java/lang/Enum.java

My build.gradle contains :

buildTypes {
    release {
        runProguard true
        proguardFile file('./proguard-project.txt')
        signingConfig signingConfigs.release
    }
}

My proguard-project.txt contains

-useuniqueclassmembernames
-keepattributes SourceFile,LineNumberTable

+ a bunch of keep class, dontnote, dontwarn,...

When I remove ProGuard from build.gradle it do not crash.

When I was using ProGuard from an Ant build it worked (I recently migrated to Gradle).

Any known issue with Gradle + ProGuard ?

Thanks

Answer 1

You have to tell ProGuard to keep some enum methods.

The Android SDK tools use this ProGuard configuration to achieve it:

# For enumeration classes, see http://proguard.sourceforge.net/manual/examples.html#enumerations
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

You can either add the above rule to your ProGuard configuration or you can (what I'd prefer) include the default Android rules:

minifyEnabled true
proguardFile getDefaultProguardFile('proguard-android.txt')
proguardFile file('./proguard-project.txt')