如何在滚动到Angular 8中的特定元素时动态更改类？

import { Component, ViewChild, ElementRef } from '@angular/core';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.css']
})
export class MyComponent {
  @ViewChild('myElement', {static: false}) myElement: ElementRef;
}

ngOnInit() {
  const options = {
    root: null,
    rootMargin: '0px',
    threshold: 0.5 // 可见性阈值，表示元素可见度达到50%时触发回调函数
  };

  const callback = (entries, observer) => {
    entries.forEach(entry => {
      if (entry.isIntersecting) {
        // 当元素进入视口时，添加或移除类
        this.myElement.nativeElement.classList.add('my-class');
      } else {
        // 当元素离开视口时，移除类
        this.myElement.nativeElement.classList.remove('my-class');
      }
    });
  };

  const observer = new IntersectionObserver(callback, options);
  observer.observe(this.myElement.nativeElement);
}

.my-class {
  /* 添加或修改特定元素的样式 */
}