I need to call the function only on my root page. but this gets call on all pages ionic 2

The code is as follow

constructor(public platform: Platform,public alertCtrl:AlertController) {

	platform.ready().then(() => {
		 platform.registerBackButtonAction(()=>this.myHandlerFunction())
		StatusBar.styleDefault();
		Splashscreen.hide();
	
	});
}


myHandlerFunction(){
	let alert = this.alertCtrl.create({
    title: 'Exit?',
    message: 'Do you want to exit the app?',
    buttons: [
      {
        text: 'Cancel',
        role: 'cancel',
        handler: () => {

        }
      },
      {
        text: 'Exit',
        handler: () => {
          this.platform.exitApp();
        }
      }
    ]
  });
  alert.present();

}	

I need the myHandlerFunction() to be called on the Homepage only