使用 templateUrl 中的条件在移动或桌面模板之间切换(Angular 7)

问题描述

我想根据屏幕宽度在桌面模板和移动模板之间切换，以确保我的应用程序具有响应性.我正在尝试执行以下操作:

I want to switch between a desktop and mobile template depending on the screen width to ensure my application is responsive. I am trying to do the following:

@Component({
    selector: 'app-root',
    templateUrl: "./" + (window.innerWidth < 768) ? "app.component.html" : "app.component.mobile.html",
    styleUrls: ['./app.component.css']
})

然而，这是行不通的.代替模板加载，字符串 "app.component.html" 出现在屏幕上.

However, this is not working. Instead of the template loading, the string, "app.component.html", appears on the screen instead.

更有趣的是，如果我使用以下内容:

What is even more interesting is that, if I use the following:

@Component({
    selector: 'app-root',
    templateUrl: "./" + (false) ? "app.component.html" : "app.component.mobile.html",
    styleUrls: ['./app.component.css']
})

页面仍然只显示字符串"app.component.html".

The page still only shows the string "app.component.html".

是否不支持使用条件语句作为 @Component 装饰器中 templateUrl 字段的值?

Is there no support for using conditional statements as the value for the templateUrl field in the @Component decorator?

如果不是，我可以使用什么替代解决方案来实现这种仍然模块化并遵循最佳实践的响应能力?

If not, what is an alternative solution I could use to achieve this level of responsiveness that is still modular and follows best practices?

更新:我通过使用 ng serve --aot 而不是 ng serve 来实现这一点.但是，我决定不考虑这个想法，因为它不会随着窗口大小调整而切换模板.

Update: I got this to work by using ng serve --aot instead of just ng serve. However, I decided to not go through with this idea because it does not switch templates as the window resizes.

推荐答案

你在这里的方法是错误的.模板在构建时分配给组件，而不是运行时，Angular 将构建它的所有组件，早在任何窗口存在且具有写入条件的宽度之前.您需要设置逻辑来告诉您的应用何时显示哪个组件.

your approach here is off. Templates are assigned to components at build time, not runtime and Angular will build all of it's components, well before any window exists with a width to write a conditional off of. You need to set up logic to tell your app when to show which component.

此处的最佳实践"(IMO)，如果您不能进行响应式设计(注意:了解您的受众以及应用程序的使用方式很重要.我总是尝试选择移动优先的响应式设计，但也要认识到这并不总是合适的)，是有 2 个组件，并使用路由保护来强制执行正确的组件.

The "best practice" (IMO) here, if you can't do responsive design (note: it's important to understand your audience and how the app will be used. I always try to opt for a mobile first responsive design, but also recognize this isn't always appropriate), is to have 2 components, and use route guards to enforce the correct component.

@Injectable()
export class MobileGuard implements CanActivate {

  constructor(
    private router: Router
  ) { }

  canActivate() {

    if (window.innerWidth >= 768) {
      this.router.navigate(['/']);
      return false;
    }

    return true;
  }
}

@Injectable()
export class DesktopGuard implements CanActivate {

  constructor(
    private router: Router
  ) { }

  canActivate() {

    if (window.innerWidth < 768) {
      this.router.navigate(['/m/']);
      return false;
    }

    return true;
  }
}

然后像这样定义你的路由结构:

then define your routing structure somewhat like this:

const routes: Routes = [
  {
    path: '',
    component: AppComponent,
    canActivate: [DesktopGuard],
    children: [... desktop routes ...]
  },
  {
    path: 'm',
    component: MobileAppComponent,
    canActivate: [MobileGuard],
    children: [... mobile routes ...]
  }
]

至于组件本身，您的移动组件只是扩展了您的非移动组件并关联了不同的模板/样式.

as for the components themselves, your mobile component just extends your non mobile component and has a different template / styles associated.

这里的另一种方法是做这样的事情:

an alternative approach here is to do something like this:

export class WrapperAppComponent {
    isMobile: boolean;

    constructor() {
      this.isMobile = window.innerWidth < 768;
    }
}

模板如下:

<desktop-app *ngIf="!isMobile"></desktop-app>
<mobile-app *ngIf="isMobile>></mobile-app>

但这不是一种可扩展性很强的方法，并且具有相同的组件重复".

but this isn't a very scalable approach and has the same "duplication" of components.

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