onKeyboardShow/onKeyboardHide events are not firing in Ionic 4

Ionic Framework ionic-v3
1

Hi,

I have added the keyboard plugin. https://ionicframework.com/docs/native/keyboard. Added the following code in the constructor but the below events are not firing.

    this.onShowSubscription = this.keyboard.onKeyboardShow().subscribe((e)=> {
        let bodyMove = <HTMLElement>document.querySelector("#footer");
        let  bodyMoveStyle = bodyMove.style;
        bodyMoveStyle.display = "none";
    });
    this.onHideSubscription = this.keyboard.onKeyboardHide().subscribe(()=> {
        let bodyMove = <HTMLElement>document.querySelector("#footer");
        let  bodyMoveStyle = bodyMove.style;
        bodyMoveStyle.display = "block";
    });

Thanks in advance.