include ../_util-fns

a(id='top')
:marked
  Our app should be able to make the browser title bar say whatever we want it to say.
  This cookbook explains how to do it.
  
  应用程序应该能让浏览器标题栏显示我们想让它显示的内容。本*烹饪宝典*解释怎么做。
:marked
  **See the <live-example name="cb-set-document-title"></live-example>**.
  
  **参见<live-example name="cb-set-document-title">在线例子</live-example>**。
  
.l-sub-section
  img(src='/resources/images/devguide/plunker-separate-window-button.png' alt="pop out the window" align="right" style="margin-right:-20px")
  :marked
    To see the browser Title bar changes,
    pop out the preview window by clicking the blue 'X' button in the upper right corner.
    
    要看到浏览器标题的变化，点击预览窗口右上角的'X'按钮，弹出窗口。
:marked
  ## The problem with *&lt;title&gt;*
  
  ## *&lt;title&gt;*的问题
  
  The obvious approach is to bind a property of the component to the HTML `<title>` like this:
  
  显而易见的方法是把组件的属性绑定到HTML的`<title>`标签上，像这样：
  
code-example(format='')
  &lt;title&gt;{{This_Does_Not_Work}}&lt;/title&gt;
:marked
  Sorry but that won't work.
  The root component of our application is an element contained within the `<body>` tag.
  The HTML `<title>` is in the document `<head>`, outside the body, making it inaccessible to Angular data binding.
  
  抱歉，这样不行。我们应用程序的根组件是一个包含在`<body>`标签里的元素。该HTML的`<title>`在文档的`<head>`元素里，在`<body>`之外，Angular的数据绑定无法访问到它。

  We could grab the browser `document` object and set the title manually.
  That's dirty and undermines our chances of running the app outside of a browser someday.
  
  可以从浏览器获得`document`对象，并且手动设置标题。但是这样看起来很脏，而且将无法在浏览器之外运行应用程序。
  
.l-sub-section
  :marked
    Running your app outside a browser means that you can take advantage of server-side
    pre-rendering for near-instant first app render times and for SEO.  It means you could run from
    inside a Web Worker to improve your app's responsiveness by using multiple threads.  And it
    means that you could run your app inside Electron.js or Windows Universal to deliver it to the desktop.
    
    在浏览器外运行应用程序意味着：利用服务器端预先渲染，为应用程序实现几乎实时的首次渲染，同时还能支持SEO(搜索引擎优化)。
    意味着你可以在一个Web Worker中运行你的应用程序，通过多线程技术增强应用程序的响应性。
    还意味着你可以在Electron.js或者Windows Universal里面运行，发布到桌面环境。

:marked
  ## Use the *Title* service
  
  ## 使用*Title*服务
  
  Fortunately, Angular bridges the gap by providing a `Title` service as part of the *Browser platform*.
  The [Title](../api/platform-browser/index/Title-class.html) service is a simple class that provides an API
  for getting and setting the current HTML document title:
    
  幸运的是，Angular在*浏览器平台*的包中，提供了一个`Title`服务，弥补了这种差异。
  [Title](../api/platform/browser/Title-class.html)服务是一个简单的类，提供了一个API，用来获取和设置当前HTML文档的标题。

  * `getTitle() : string` &mdash; Gets the title of the current HTML document.
  
  * `getTitle(): string` —— 获取当前HTML文档的标题。
  
  * `setTitle( newTitle : string )` &mdash; Sets the title of the current HTML document. 
  
  * `setTitle( newTitle: string)` —— 设置当前HTML文档的标题。

  Let's inject the `Title` service into the root `AppComponent` and expose a bindable `setTitle` method that calls it:
  
  我们来把`Title`服务注入到根组件`AppComponent`，并暴露出可供绑定的`setTitle`方法让别人来调用该服务：

+makeExample( "cb-set-document-title/ts/app/app.component.ts", "class", "app/app.component.ts (class)" )(format='.')
:marked
  We bind that method to three anchor tags and, voila!
  
  我们把这个方法绑定到三个A标签，瞧瞧！
  
figure.image-display
   img(src="/resources/images/cookbooks/set-document-title/set-title-anim.gif" alt="Set title")

:marked
  Here's the complete solution
  
  这里是完整的方案(代码)。

+makeTabs(
  `cb-set-document-title/ts/app/main.ts,
   cb-set-document-title/ts/app/app.module.ts,
   cb-set-document-title/ts/app/app.component.ts`, 
  '', 
  'app/main.ts, app/app.module.ts, app/app.component.ts' )

//
  Todo: tie this back to the router so we can see how to use this Title service to (re)set the title
  that appears in the window navigation history and shows up in the back/forward buttons
  during routing.

  See https://github.com/angular/angular/issues/7630#issuecomment-198328802

.l-main-section
:marked
  ## Why we provide the *Title* service in *bootstrap*
  
  ## 为什么要在*bootstrap*里面提供这个*Title*服务
  
  We generally recommended providing application-wide services in the root application component, `AppComponent`.
  
  我们通常会推荐在应用程序的根组件`AppComponent`中提供应用程序级的服务。
  
  Here we recommend registering the title service during bootstrapping, 
  a location we reserve for configuring the runtime Angular environment.
  
  但这里，我们推荐在引导过程中注册这个Title服务，这个位置是为设置Angular运行环境而保留的。
  
  That's exactly what we're doing.
  The `Title` service is part of the Angular *browser platform*.
  If we bootstrap our application into a different platform,
  we'll have to provide a different `Title` service that understands the concept of a "document title" for that specific platform.
  Ideally the application itself neither knows nor cares about the runtime environment.
  
  我们的做法正是如此。这里的`Title`服务是Angular*浏览器平台*的一部分。如果在其它平台上引导应用程序，就得提供另一个专为那个平台准备的`Title`服务。
:marked
  [Back to top](#top)
  
  [回到顶部](#top)
