问如何知道Unity UI按钮是否被按下？

EN

using UnityEngine;
using UnityEngine.EventSystems;

public class LongPress : MonoBehaviour, IPointerDownHandler, IPointerUpHandler {

  private bool isDown;
  private float downTime;

  public void OnPointerDown(PointerEventData eventData) {
    this.isDown = true;
    this.downTime = Time.realtimeSinceStartup;
  }

  public void OnPointerUp(PointerEventData eventData) {
    this.isDown = false;
  }

  void Update() {
    if (!this.isDown) return;
    if (Time.realtimeSinceStartup - this.downTime > 2f) {
      print("Handle Long Tap");
      this.isDown = false;
    }
  }

}