从ngFor中删除元素时，如何利用Angular 7中的退出动画？

<div *ngFor="let item of items" [@itemAnimation]="item.state" (click)="removeItem(item)">
  {{ item.name }}
</div>

@keyframes fadeOut {
  0% { opacity: 1; }
  100% { opacity: 0; }
}

.item-animation {
  animation: fadeOut 0.5s;
}

import { trigger, state, style, transition, animate } from '@angular/animations';

@Component({
  selector: 'app-example',
  templateUrl: './example.component.html',
  styleUrls: ['./example.component.css'],
  animations: [
    trigger('itemAnimation', [
      state('removed', style({ opacity: 0 })),
      transition('* => removed', [
        animate('0.5s')
      ])
    ])
  ]
})
export class ExampleComponent {
  items: any[] = [
    { name: 'Item 1', state: 'active' },
    { name: 'Item 2', state: 'active' },
    { name: 'Item 3', state: 'active' }
  ];

  removeItem(item: any) {
    item.state = 'removed';
    setTimeout(() => {
      this.items = this.items.filter(i => i !== item);
    }, 500);
  }
}