如何自定义angular dart中的元素

import 'package:angular/angular.dart';
import 'package:angular_components/angular_components.dart';

@Component(
  selector: 'custom-element',
  styleUrls: ['custom_element.css'],
  templateUrl: 'custom_element.html',
  directives: [materialDirectives],
  providers: [materialProviders],
)
class CustomElementComponent {}

<div>
  <h1>Custom Element</h1>
  <!-- Add your custom HTML here -->
</div>

/* Add your custom CSS here */

import 'package:angular/angular.dart';
import 'package:angular_components/angular_components.dart';
import 'custom_element.dart';

@Component(
  selector: 'my-app',
  styleUrls: ['app_component.css'],
  templateUrl: 'app_component.html',
  directives: [materialDirectives, CustomElementComponent],
  providers: [materialProviders],
)
class AppComponent {}

<custom-element></custom-element>