[SOLVED]GameSharing API

Hello. thank you for your time
I am trying to use the google play game service in my game.
and I try to use the API GameSharing
http://www.cocos2d-x.org/hub/156
I follow his tutorial here

I did everything in the tutorial
my game can sign in the google game play service.

however, I could not call functions in the GameSharing.h

bool HelloWorld::init()
{
//////////////////////////////
// 1. super init first
if ( !Layer::init() )
{
return false;
}
GameSharing::ShowAchievementsUI();

return true;

}

When I run the game, this error shows up.
25181-25202/testing.play.game E/JniHelper: Failed to find static method id of isGPGSupported

I do not familiar with java code. how could I fix this problem?
thank you for your time

[solved] just forgot to put the java files. they are not in the tutorial