Integrate Unity App into Android project

Hello!I have a Unity3D App and I want to integrate it in an Android project. I have followed this post (https://developer.vuforia.com/resou...roid-activity-and-adding-custom-views-eclipse) and I got it with a small project I implemented just for this.But now that I am trying to integrate a bigger project (It should not be any difference) I am getting a NoClassDefFoundError for this class: com.unity3d.player.UnityPlayer. I have included classes.jar in my project and QCARUnityPlayer.jar and Vuforia.jar.Has anyone faced with this problem before? Please any help will be appreciated. Also if you know any tutorial in order to integrate a Unity project into Android project...Thank you in advance!