当我点击开关时，如何在Angular中切换深色主题？

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class ThemeService {
  isDarkTheme: boolean = false;

  toggleTheme() {
    this.isDarkTheme = !this.isDarkTheme;
    if (this.isDarkTheme) {
      // 应用深色主题样式
      document.body.classList.add('dark-theme');
    } else {
      // 移除深色主题样式
      document.body.classList.remove('dark-theme');
    }
  }
}

import { Component } from '@angular/core';
import { ThemeService } from './theme.service';

@Component({
  selector: 'app-root',
  template: `
    <button (click)="toggleTheme()">切换主题</button>
    <div [ngClass]="{ 'dark': themeService.isDarkTheme }">
      <!-- 页面内容 -->
    </div>
  `,
  styles: [`
    .dark {
      background-color: #333;
      color: #fff;
    }
  `]
})
export class AppComponent {
  constructor(public themeService: ThemeService) {}

  toggleTheme() {
    this.themeService.toggleTheme();
  }
}