How to make Android Plugin for Unity3d

I am trying to build Android Plugin for Unity3D. My Android Project is a Library project and i have used it on different Android Applications. This Library project simply displays a Dialog on my Main Application, having some images. An xml layout is attached to this Dialog to set Image placements.

Now I want to use the same Android Library Project with Unity3D. I have followed a simple tutorial that lets me communicate between Android and Unity3D.

So in Unity3D using AndroidJavaClass, when I call this function to display the dialog containing images, it shows nothing and with no error.

Is there something I should change in my AndroidManifest or what should I change in my code to display this dialoge?

Please Help me out of this.

Update-1

This is the code on Unity3D side this is the bridge Class.

 using UnityEngine;
 using System.Collections;
 
 public class Test : MonoBehaviour
 {
     AndroidJavaClass androidclass = null;
 
     // Use this for initialization
     void Start()
     {
         AndroidJavaClass activityClass = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
         AndroidJavaObject activityContext = activityClass.GetStatic<AndroidJavaObject>("currentActivity");
 
         androidclass = new AndroidJavaClass("com.mycompany.myproject.androidbridgeclass");
                 
         
     }
 
     void Update()
     {
         if (Input.GetMouseButtonDown(0))
         {
             
         androidclass.CallStatic("displayDialogWithImages");
         }
 
         if (Input.GetKeyDown(KeyCode.Escape))
         {
             Application.Quit();
         }
     }
 }