Android Java Plugin For Unity Object with null ptr!

So I wanted to test out writing custom plugins for unity. I am using Android Studio 1.1.0. I found tutorial to write a plugin, and it works when defined in manifest as MainActivity.But if I add it as secondary plugin I am having the following error:

 04-21 15:13:58.446: I/Unity(23041): Exception: JNI: Init'd AndroidJavaObject with null ptr!
 04-21 15:13:58.446: I/Unity(23041):   at UnityEngine.AndroidJavaObject..ctor (IntPtr jobject) [0x00000] in :0 
 04-21 15:13:58.446: I/Unity(23041):   at UnityEngine.AndroidJavaObject.AndroidJavaObjectDeleteLocalRef (IntPtr jobject) [0x00000] in :0 
 04-21 15:13:58.446: I/Unity(23041):   at UnityEngine.AndroidJavaObject._GetStatic[AndroidJavaObject] (System.String fieldName) [0x00000] in :0 
 04-21 15:13:58.446: I/Unity(23041):   at UnityEngine.AndroidJavaObject.GetStatic[AndroidJavaObject] (System.String fieldName) [0x00000] in :0 
 04-21 15:13:58.446: I/Unity(23041):   at Share.callShareApp () [0x00000] in :0 
 04-21 15:13:58.446: I/Unity(23041):   at Share.OnGUI () [0x00000] in :0 
 04-21 15:13:58.446: I/Unity(23041):  

My Java code:

  package com.example.tomek.shareproject;
     
             import android.content.Intent;
             import com.unity3d.player.UnityPlayerActivity;
           //  import android.content.Context;
             import android.os.Bundle;
     public class MainActivity extends UnityPlayerActivity {
         public static MainActivity ctx;
         //@Override
         protected void onCreate(Bundle savedInstanceState) {
             super.onCreate(savedInstanceState);
             MainActivity.ctx = this;
         }
     
         public void shareText(String subject, String body) {
             Intent sharingIntent = new Intent(android.content.Intent.ACTION_SEND);
             sharingIntent.setType("text/plain");
             sharingIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, subject);
             sharingIntent.putExtra(android.content.Intent.EXTRA_TEXT, body);
             startActivity(Intent.createChooser(sharingIntent, "Share via"));
         }
     
     }
     
 

And My unity code:

 using UnityEngine;
 using System.Collections;
 
 public class Share : MonoBehaviour {
     
  
  string subject = "TITLE";
  string body = "TEST BODY TEXT";
  
  public void callShareApp()
  {
 
 #if UNITY_ANDROID
      AndroidJavaClass cls = new AndroidJavaClass("com.example.tomek.shareproject.MainActivity");
   
      
      AndroidJavaObject obj = cls.GetStatic<AndroidJavaObject> ("ctx");
      obj.Call("shareText", subject, body);
 #endif
 
  }
 
     void OnGUI()
     {
         if (GUI.Button(new Rect(10, 10, 50, 50), "Click me "))
             callShareApp();
 
     }
 }

Also my manifest:

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
       package="com.unity3d.playe"
       android:versionCode="1"
       android:versionName="1.0">
     <uses-sdk android:minSdkVersion="9" />
     <application android:label="@string/app_name">
         <activity android:name="com.unity3d.player.UnityPlayerActivity"
                   android:label="@string/app_name">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
           <meta-data android:name="unityplayer.UnityActivity" android:value="true" />
           <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="false" />
         </activity>
       <!-- Required by my Plugin -->
       <activity android:name="com.example.tomek.shareproject.MainActivity" />
     </application>
 </manifest>

So I read few dozens of topic regarding this error but cannot find a solution. Can anybody point out where I might go wrong about it ?

Best Regards