Android Unity plugin - Class not found exception

Question

I want to export an android library to Unity, but that Android gives the following error:

05-14 12:58:10.601 18408-18408/? E/AndroidRuntime: FATAL EXCEPTION: main
                                               Process: com.joostverbraeken.weargame, PID: 18408
                                               java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.joostverbraeken.weargame/com.joostverbraeken.weargame.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.joostverbraeken.weargame.MainActivity" on path: DexPathList[[zip file "/data/app/com.joostverbraeken.weargame-1/base.apk"],nativeLibraryDirectories=[/data/app/com.joostverbraeken.weargame-1/lib/arm, /data/app/com.joostverbraeken.weargame-1/base.apk!/lib/armeabi-v7a, /vendor/lib, /system/lib]]
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2332)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2481)
at android.app.ActivityThread.access$900(ActivityThread.java:153)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1349)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5436)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:735)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
                                                    Caused by: java.lang.ClassNotFoundException: Didn't find class "com.joostverbraeken.weargame.MainActivity" on path: DexPathList[[zip file "/data/app/com.joostverbraeken.weargame-1/base.apk"],nativeLibraryDirectories=[/data/app/com.joostverbraeken.weargame-1/lib/arm, /data/app/com.joostverbraeken.weargame-1/base.apk!/lib/armeabi-v7a, /vendor/lib, /system/lib]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2322)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2481) 
at android.app.ActivityThread.access$900(ActivityThread.java:153) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1349) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5436) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:735) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625) 
                                                    Suppressed: java.lang.NoClassDefFoundError: com.joostverbraeken.weargame.MainActivity
at dalvik.system.DexFile.defineClassNative(Native Method)
at dalvik.system.DexFile.defineClass(DexFile.java:226)
at dalvik.system.DexFile.loadClassBinaryName(DexFile.java:219)
at dalvik.system.DexPathList.findClass(DexPathList.java:338)
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:54)
        ... 13 more
                                                    Suppressed: java.lang.ClassNotFoundException: com.joostverbraeken.weargame.MainActivity
at java.lang.Class.classForName(Native Method)
at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
        ... 12 more
                                                    Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack trace available

My AndroidManifest (I copied the one from my library into Unity) is as follows:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.joostverbraeken.weargame">

    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

    <application android:icon="@mipmap/ic_launcher" android:label="@string/app_name">
        <activity android:name=".MainActivity"
            android:label="@string/app_name"
            android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen">
        <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

The dependencies are fairly straightforward and are declared in Gradle:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'], exclude: ['classes.jar'])
    provided files('libs/classes.jar')
    wearApp project(':wear')
    compile 'com.google.android.gms:play-services:8.4.0'
    compile 'com.android.support:support-v4:23.4.0'
}

On a forum I read Unity needed to have the dependencies copied into Assets/Plugins/Android, although I'm using an aar instead of a jar. So I copied support-v4-23.3.0-sources.jar into Assets/Plugins/Android as well, but play-services-8.4.0.jar not because it's not included in the Android system files. play-services-8.4.0.aar is included, but if I copy that to Unity I get the following error:

Moving
Temp/StagingArea\android-libraries\play-services-8.4.0\classes.jar to
Temp/StagingArea\android-libraries\play-services-8.4.0\bin\classes.jar:
The system cannot find the file specified.

Does anybody have an idea how to solve the ClassNotFoundException?

Answer 1

I believe this is caused by AndroidManifest.xml which has something conflict with Unity generated AndroidManiefst.xml. It's not friendly that unity does not give us any error messages in this case and it really sucks that only export eclipse project.

I came across the same exception today, so I did some further test and found the ClassNotFoundException can only be produced in Activity classes. So I exported the project and import the project into AndriodStudio and recompiled it. I got some error in AndroidManifest.xml like the incorrect theme or incorrect icon ,etc.

After update all incorrect configurations in AndriodManifest.xml and rebuild the AAR, everything worked fine.

Hope this can help you.