Angular 2 - 如何有条件地为我的组件添加样式？

Question

我有一个带有样式表的组件，可以像这样正确加载：

@Component({
  selector: 'open-account',
  styleUrls: ['open-account.component.scss'],
  templateUrl: './open-account.component.html',
})

我想有条件地加载另一个样式表，如果字符串widget=true存在于url中，但无论如何都无法工作。 我努力了：

var stylesArr = ['open-account.component.scss'];
if (window.location.href.indexOf('widget=true') > -1) stylesArr.push('open-account-widget-styles.component.scss');

@Component({
  selector: 'open-account',
  styleUrls: stylesArr,
  templateUrl: './open-account.component.html',
})

和

var stylesArr = ['./open-account.component.scss'];
if (window.location.href.indexOf('widget=true') > -1) stylesArr.push('./open-account-widget-styles.component.scss');

@Component({
  selector: 'open-account',
  styleUrls: stylesArr,
  templateUrl: './open-account.component.html',
})

和

@Component({
  selector: 'open-account',
  styleUrls: ['open-account.component.scss', 'open-account-widget-styles.component.scss'].filter(elem => {
    if (elem === 'open-account.component.scss') return true;
    if (elem === 'open-account-widget-styles.component.scss' && window.location.href.indexOf('widget=true') > -1) return true;
  }),
  templateUrl: './open-account.component.html',
})

并在我的HTML顶部：

<style type="text/css" *ngIf="false">
(the 'false' would be a variable, but putting in false doesnt even stop the style from loading)
...
</style>

如果有条件地加载这样的附加样式表，我该怎么办？ 我不知道还有什么可以尝试。

Answer 1

 import { Component, Inject } from '@angular/core';
 import { DOCUMENT } from '@angular/platform-browser';

 @Component({
 })

 export class SomeComponent {

    constructor (@Inject(DOCUMENT) private document) { }

        LightTheme() {
            this.document.getElementById('theme').setAttribute('href', 'light-theme.css');


        DarkTheme() {
            this.document.getElementById('theme').setAttribute('href', 'dark-theme.css');
    }
}

Answer 2

我发现它的唯一方法是这样做：

addStyleSheet() {
  var headID = document.getElementsByTagName('head')[0];
  var link = document.createElement('link');
  link.type = 'text/css';
  link.rel = 'stylesheet';
  link.id = 'widget_styles';
  headID.appendChild(link);

  link.href = './app/open-account/open-account-widget-styles.component.css';
}

ngOnInit() {
  this.addStyleSheet();
}