在使用trackBy进行轮询时，强制刷新组件的视图。可以通过触发CD检测 (ChangeDetectorRef.detectChanges())或者强制刷新 (this.ngZone.run(() => {}))来实现。以下是示例代码：

@Component({
  selector: 'my-component',
  template: `
    

      
{{ item }}
    
  `
})
export class MyComponent implements OnInit, OnDestroy {
  items: string[] = [];
  private subscription: Subscription;
  
  constructor(private myService: MyService, private cd: ChangeDetectorRef, private ngZone: NgZone) {}
  
  ngOnInit() {
    this.subscription = timer(0, 1000).subscribe(() => {
      this.myService.getItems().subscribe(items => {
        this.items = items;
        // 触发CD检测
        this.cd.detectChanges();
        // 或者强制刷新
        this.ngZone.run(() => { });
      });
    });
  }
  
  ngOnDestroy() {
    this.subscription.unsubscribe();
  }
  
  trackByFn(index: number, item: string) {
    return item;
  }
}