Back button handling in cocos2d-x 3.0 with windows phone

It is very easy to get back button callback in your *.cpp.
There is some simple steps to solve the issue.
1. first create a class which provide callback in your *.cpp
/*///////////////////////////////////////////////////////////////////////////////////////////////////////////
That cpp provide call back to your *.cpp just inherit that
/////////////////////////////////////////////////////////////////////////////////////////////*/
namespace PhoneDirect3DXamlAppComponent
{
class backcall//,public cocos2d::CCTouchDelegate,public CCKeypadDelegate
{ 
public:

virtual  void backCalled();
static backcall* getInstance();
backcall();
~backcall();
static backcall* myptr; 
};
}
#endif
///////////////////////////////////////////////////////////////////////////////////////////////////
#include "backcall.h"
using namespace PhoneDirect3DXamlAppComponent;
 void backcall::backCalled()
 {
 }
 backcall* backcall::myptr=NULL; 
backcall* backcall::getInstance()
{
return myptr;
}

backcall::backcall()
{


myptr=this;


}
backcall::~backcall()
{
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
2. then open  yourDrive\cocos2d-x-3.0\cocos\2d\platform\wp8-xaml\cpp\Cocos2dRenderer.cpp
3. search
void Cocos2dRenderer::OnBackKeyPress()
{
    // handle the backkey in your app here.
    // call Cocos2dEvent::TerminateApp if it is time to exit your app.
    // ie. the user is on your first page and wishes to exit your app.
 //   m_delegate->Invoke(Cocos2dEvent::TerminateApp); comment that line 
//and setcallback to yor *.cpp
if(backcall::getInstance())
{
backcall::getInstance()->backCalled();
}
}


for example
#include "backcall.h"
using namespace PhoneDirect3DXamlAppComponent;
class arpitLayer ,public Layer . public  backcall
{
virtual  void backCalled();
}
in cpp
void arpitLayer :: backCalled()
{
//Now you are happy to manage your back code here

}


/////////////////////////////////////////////////////////////////////////