Angular2 whenStable()不使用observable？

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

@Component({
  selector: 'app-example',
  template: `
    <button (click)="doAsyncTask()">Do Async Task</button>
  `
})
export class ExampleComponent {
  constructor(private ngZone: NgZone) {}

  doAsyncTask() {
    // Perform async task here

    // Use Promise to handle async completion
    const promise = new Promise((resolve, reject) => {
      // Simulate async task completion
      setTimeout(() => {
        resolve();
      }, 2000);
    });

    // Execute callback when async task is completed
    promise.then(() => {
      this.ngZone.run(() => {
        // Code to be executed when async task is completed
        console.log('Async task completed');
      });
    });
  }
}