116 lines
5.3 KiB
Markdown
116 lines
5.3 KiB
Markdown
{@a top}
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# Set the Document Title
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# 设置文档标题
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Your app should be able to make the browser title bar say whatever you want it to say.
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This cookbook explains how to do it.
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应用程序应该能让浏览器标题栏显示你想让它显示的内容。本文会解释怎么做。
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See the <live-example name="set-document-title"></live-example>.
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参见<live-example name="set-document-title"></live-example>
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## The problem with *<title>*
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## *<title>*的问题
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The obvious approach is to bind a property of the component to the HTML `<title>` like this:
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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：
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<code-example format=''>
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<title>{{This_Does_Not_Work}}</title>
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</code-example>
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Sorry but that won't work.
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The root component of the application is an element contained within the `<body>` tag.
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The HTML `<title>` is in the document `<head>`, outside the body, making it inaccessible to Angular data binding.
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抱歉，这样不行。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。
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You could grab the browser `document` object and set the title manually.
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That's dirty and undermines your chances of running the app outside of a browser someday.
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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。
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<div class="alert is-helpful">
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Running your app outside a browser means that you can take advantage of server-side
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pre-rendering for near-instant first app render times and for SEO. It means you could run from
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inside a Web Worker to improve your app's responsiveness by using multiple threads. And it
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means that you could run your app inside Electron.js or Windows Universal to deliver it to the desktop.
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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)。
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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。
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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。
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</div>
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## Use the `Title` service
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## 使用 `Title` 服务
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Fortunately, Angular bridges the gap by providing a `Title` service as part of the *Browser platform*.
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The [Title](api/platform-browser/Title) service is a simple class that provides an API
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for getting and setting the current HTML document title:
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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。
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[Title](api/platform-browser/Title)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。
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* `getTitle() : string`—Gets the title of the current HTML document.
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`getTitle(): string` —— 获取当前 HTML 文档的标题。
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* `setTitle( newTitle : string )`—Sets the title of the current HTML document.
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`setTitle( newTitle: string)` —— 设置当前 HTML 文档的标题。
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You can inject the `Title` service into the root `AppComponent` and expose a bindable `setTitle` method that calls it:
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你可以把 `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：
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<code-example path="set-document-title/src/app/app.component.ts" region="class" title="src/app/app.component.ts (class)" linenums="false"></code-example>
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Bind that method to three anchor tags and voilà!
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把这个方法绑定到三个 A 标签，瞧瞧！
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<figure>
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<img src="generated/images/guide/set-document-title/set-title-anim.gif" alt="Set title">
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</figure>
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Here's the complete solution:
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这里是完整的方案(代码)。
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<code-tabs>
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<code-pane title="src/main.ts" path="set-document-title/src/main.ts"></code-pane>
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<code-pane title="src/app/app.module.ts" path="set-document-title/src/app/app.module.ts"></code-pane>
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<code-pane title="src/app/app.component.ts" path="set-document-title/src/app/app.component.ts"></code-pane>
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</code-tabs>
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## Why provide the `Title` service in `bootstrap`
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## 为什么要在 *bootstrap* 里面提供这个 *Title* 服务
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Generally you want to provide application-wide services in the root application component, `AppComponent`.
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你通常会在应用程序的根组件 `AppComponent` 中提供应用程序级的服务。
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This cookbook recommends registering the title service during bootstrapping,
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a location you reserve for configuring the runtime Angular environment.
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但这里，要在引导过程中注册这个 Title 服务，这个位置是为你设置 Angular 运行环境而保留的。
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That's exactly what you're doing.
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The `Title` service is part of the Angular *browser platform*.
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If you bootstrap your application into a different platform,
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you'll have to provide a different `Title` service that understands
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the concept of a "document title" for that specific platform.
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Ideally, the application itself neither knows nor cares about the runtime environment.
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你的做法正是如此。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。
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