Error Exception: JNI: Init'd AndroidJavaClass with null ptr!

[jianloong92]

code:
internal AndroidJavaObject GetActivity() {

        AndroidJavaClass jc = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
        if (jc == null) {
            throw new System.Exception("Could not get class com.unity3d.player.UnityPlayer.");
        }
        AndroidJavaObject activity = jc.GetStatic<AndroidJavaObject>("currentActivity");
        if (activity == null) {
            throw new System.Exception("Could not get class current activity from UnityPlayer.");
        }
        return activity;
    }

problem:
Exception: JNI: Init'd AndroidJavaClass with null ptr!
UnityEngine.AndroidJavaClass..ctor (IntPtr jclass)
UnityEngine.AndroidJavaObject.get_JavaLangClass ()
UnityEngine.AndroidJavaObject.FindClass (System.String name)
UnityEngine.AndroidJavaClass._AndroidJavaClass (System.String className)
UnityEngine.AndroidJavaClass..ctor (System.String className)
GooglePlayGames.Android.AndroidClient.GetActivity () (at assets/GooglePlayGames/Platforms/Android/AndroidClient.cs:271)
GooglePlayGames.Android.AndroidClient.RunOnUiThread (System.Action action) (at assets/GooglePlayGames/Platforms/Android/AndroidClient.cs:283)
GooglePlayGames.Android.AndroidClient..ctor () (at assets/GooglePlayGames/Platforms/Android/AndroidClient.cs:63)
GooglePlayGames.PlayGamesClientFactory.GetPlatformPlayGamesClient () (at assets/GooglePlayGames/Platforms/PlayGamesClientFactory.cs:26)
GooglePlayGames.PlayGamesPlatform.Authenticate (ILocalUser unused, System.Action1 callback, Boolean silent) (at assets/GooglePlayGames/ISocialPlatform/PlayGamesPlatform.cs:157) GooglePlayGames.PlayGamesPlatform.Authenticate (ILocalUser localUser, System.Action1 callback) (at assets/GooglePlayGames/ISocialPlatform/PlayGamesPlatform.cs:132)
GooglePlayGames.PlayGamesLocalUser.Authenticate (System.Action`1 callback) (at assets/GooglePlayGames/ISocialPlatform/PlayGamesLocalUser.cs:36)
Game6_Player.Start () (at assets/game 6/script/Game6_Player.cs:124)

[danielsb]

Are you trying it on the Unity Editor? You can't test it inside Unity, you need to do it in a device running Android.