APK exploit app crashes when open

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I build and install the qark exploit app into a simulator API 21

:app:processDebugManifest
:app:processDebugResources
:app:generateDebugSources
:app:compileDebugJava
:app:preDexDebug
:app:dexDebug
:app:processDebugJavaRes UP-TO-DATE
:app:validateDebugSigning
:app:packageDebug
:app:zipalignDebug
:app:assembleDebug

BUILD SUCCESSFUL

Total time: 13.739 secs
Finish building exploit APK...

i get this error
E/AndroidRuntime( 3815): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.secbro.qark/com.secbro.qark.TopLevelActivity}: java.lang.ClassNotFoundException: Didn't find class "com.secbro.qark.TopLevelActivity" on path: DexPathList[[zip file "/data/app/com.secbro.qark-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
E/AndroidRuntime( 3815): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
E/AndroidRuntime( 3815): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
E/AndroidRuntime( 3815): at android.app.ActivityThread.access$800(ActivityThread.java:144)
E/AndroidRuntime( 3815): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
E/AndroidRuntime( 3815): at android.os.Handler.dispatchMessage(Handler.java:102)
E/AndroidRuntime( 3815): at android.os.Looper.loop(Looper.java:135)
E/AndroidRuntime( 3815): at android.app.ActivityThread.main(ActivityThread.java:5221)
E/AndroidRuntime( 3815): at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime( 3815): at java.lang.reflect.Method.invoke(Method.java:372)
E/AndroidRuntime( 3815): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
E/AndroidRuntime( 3815): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
E/AndroidRuntime( 3815): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.secbro.qark.TopLevelActivity" on path: DexPathList[[zip file "/data/app/com.secbro.qark-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
E/AndroidRuntime( 3815): at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
E/AndroidRuntime( 3815): at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
E/AndroidRuntime( 3815): at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
E/AndroidRuntime( 3815): at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
E/AndroidRuntime( 3815): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
E/AndroidRuntime( 3815): ... 10 more
E/AndroidRuntime( 3815): Suppressed: java.lang.ClassNotFoundException: com.secbro.qark.TopLevelActivity
E/AndroidRuntime( 3815): at java.lang.Class.classForName(Native Method)
E/AndroidRuntime( 3815): at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
E/AndroidRuntime( 3815): at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
E/AndroidRuntime( 3815): at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
E/AndroidRuntime( 3815): ... 13 more
E/AndroidRuntime( 3815): Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available

Start by comparing the manifest entry for com.secbro.qark.TopLevelActivity with the classes packaged in the built APK and the Gradle build output. Reproduce the install and launch on a simulator using API 21; done means the exploit app starts without the reported ClassNotFoundException.

Written by the indexing model from the issue text.