Unity3D for Android: “JNI ERROR (app bug): attempt to use stale global reference” with Incorrect Use of Prime31’s Social Networking Plugin

I was porting a Unity3D-built iOS game to Android the other day, while using the awesome Social Networking plugin from Prime31, and got this fun Java error:

E/dalvikvm( 5539): JNI ERROR (app bug): attempt to use stale global reference 0x32
E/dalvikvm( 5539): VM aborting
F/libc    ( 5539): Fatal signal 11 (SIGSEGV) at 0xdeadd00d (code=1), thread 5583 (UnityMain)
... 

The above error crashed my app consistently.

I was lucky in this case because I was fairly sure where it’s coming from, suspecting an unnecessary call to FacebookAndroid.logout() inside a check for !FacebookAndroid.isSessionValid() check. Not my proudest coding moment, for sure.

Once I put a Debug.Log() right before the FacebookAndroid.logout() call and right after. The error changed to… or perhaps a new error started showing up around the same place in the debug log:

W/dalvikvm( 2910): threadid=9: thread exiting with uncaught exception (group=0x4001d5a0)
E/AndroidRuntime( 2910): FATAL EXCEPTION: GLThread 10
E/AndroidRuntime( 2910): java.lang.NullPointerException
E/AndroidRuntime( 2910): 	at com.prime31.FacebookPlugin.logout(FacebookPlugin.java:187)
E/AndroidRuntime( 2910): 	at com.unity3d.player.UnityPlayer.nativeRender(Native Method)
E/AndroidRuntime( 2910): 	at com.unity3d.player.UnityPlayer.onDrawFrame(Unknown Source)
E/AndroidRuntime( 2910): 	at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1363)
E/AndroidRuntime( 2910): 	at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1118)
W/ActivityManager( 1323):   Force finishing activity com.companyName.MyBundleIDHere/com.unity3d.player.UnityPlayerNativeActivity

The app stopped crashing but the java.lang.NullPointerException didn’t go away either. Still looking into it.

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2 thoughts on “Unity3D for Android: “JNI ERROR (app bug): attempt to use stale global reference” with Incorrect Use of Prime31’s Social Networking Plugin

    • Sorry, so far no luck in getting the java.lang.NullPointerException to disappear. It doesn’t seem to be causing any problems when running on device, so for now I guess it’s a low priority.

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