Finding application version Name from Android

     var unityPlayerClass :AndroidJavaClass =  new AndroidJavaClass("com.unity3d.player.UnityPlayer");
     var metricsClass :AndroidJavaClass =  new AndroidJavaClass("android.util.DisplayMetrics");
     var metricsInstance :AndroidJavaObject = new AndroidJavaObject("android.util.DisplayMetrics");
             
     var activityInstance :AndroidJavaObject = unityPlayerClass.GetStatic.<AndroidJavaObject>("currentActivity");
     var windowManagerInstance :AndroidJavaObject = activityInstance.Call.<AndroidJavaObject>("getWindowManager");
     var displayInstance :AndroidJavaObject = windowManagerInstance.Call.<AndroidJavaObject>("getDefaultDisplay");
     displayInstance.Call("getMetrics", metricsInstance);
 
     var Density : float = metricsInstance.Get.<float>("density");
     var DensityDPI : int = metricsInstance.Get.<int>("densityDpi");
     var HeightPixels : int = metricsInstance.Get.<int>("heightPixels");
     var WidthPixels : int = metricsInstance.Get.<int>("widthPixels");
     var ScaledDensity : float = metricsInstance.Get.<float>("scaledDensity");
     var XDPI : float = metricsInstance.Get.<float>("xdpi");
     var YDPI : float = metricsInstance.Get.<float>("ydpi");

Using above code one can Access DisplayMetrics class of android to get Width,Height of android device. On the similar lines I am looking to get the application version. But I am stuck with the parameter part of the getPackageInfo method. In android

 pInfo = getPackageManager().getPackageInfo(getPackageName(), 0);
 version = pInfo.versionName;

this is used for getting Version Name, so how to pass two parameters to the getPackageInfo.This is what I have done till now.

 var packageManagerObject:AndroidJavaObject=new AndroidJavaObject("android.content.pm.PackageManager");
 var packInfo:AndroidJavaClass=new AndroidJavaObject("android.content.pm.PackageInfo");
 
 var packageManagerInstance :AndroidJavaObject=packageManagerObject.Call.<AndroidJavaObject>("getPackageManager");
 var packageNameInstance:AndroidJavaObject=packageManagerObject.Call.<AndroidJavaObject>("getPackageName");
         
 packageManagerInstance.Call("getPackageName",packageNameInstance,0);
 var version=packageManagerInstance.Get.<String>("versionName");
 print("Version NAMe:: "+version);

After checking this code on device it gives AndroidJavaException: java.lang.InstantiationException: Can't instantiate Landroid/content/pm/PackageManager; (abstract or interface)