网址：https://developer.apple.com/design/human-interface-guidelines/ios/app-architecture/modality/

作者：苹果公司

译者：泽泽先生 

Modality is a design technique that presents content in a temporary mode that’s separate from the user's previous current context and requires an explicit action to exit. Presenting content modally can:

模态是一种与用户当前内容文本分开的临时展现内容的设计技术，(模态)需要明确地操作才能退出。通过模态呈现的内容可以:

• Help people focus on a self-contained task or set of closely related options
• 帮助用户专注于独立任务或一系列紧密相关选项。
• Ensure that people receive and, if necessary, act on critical information
• 确保人们接收到信息，如果需要的话，可以根据关键信息采取行动。

iOS provides Alerts, Activity Views (or Share sheets), and Action Sheets that you use in specific situations in your app. To present custom modal content in your app, iOS 13 and later supports the following presentation styles.

iOS 提供警示框、活动视图（或分享视图）及供在你的应用程序特定情况下使用的动作列表，为了在应用程序中呈现定制的模态内容，iOS 13 及之后的版本支持以下呈现风格。

译者注释

为更好的理解模态，我将 iOS 设计规范中 Alerts, Activity Views,  Action Sheets 三种视图内容也在下文中进行了翻译。

Sheet

列表

The sheet presentation style appears as a card that partially covers the underlying content and dissmiss all uncovered areas to prevent interaction with them. The top edge of the parent view or a previous card is visible behind the current card to help people remember the task they suspended when they opened the card. People dismiss a card by:

工作表样式为卡片形式，其中（屏幕）部分覆盖了下层内容并使所有未覆盖部分弱化(使用黑色遮罩或高斯模糊等形式)以防止用户与这部分内容交互，父视图或前一张卡片上边缘在当前视图后方可见，从而帮助人们记住他们在打开卡片之前暂停的任务，人们通过以下方式取消卡片：

• Swiping down from the top of the screen
• 从屏幕顶部向下滑动
• Swiping down from anywhere on the screen when card content is scrolled to the top
• 当卡片内容滚动到屏幕顶端时从(屏幕)任何地方向下滑动
• Tapping a button
• 点击按钮

Use a sheet for nonimmersive modal content that doesn’t enable a complex task.

对于不支持复杂任务的非沉浸式模态内容使用列表。

Fullscreen

全屏

The fullscreen presentation style covers the entire screen. The previous view is completely covered, minimizing visual distraction. People dismiss a full-screen modal view by tapping a button.

全屏展示样式覆盖整个屏幕，前一个视图是完全被覆盖的，最大限度减少视觉干扰，人们可以通过点击按钮的方式取消全屏模态视图。

Use a full-screen modal view for immersive content — such as videos, photos, or camera views — or a complex task that benefits from a full-screen presentation, such as marking up a document or editing a photo.

对沉浸式内容使用全屏模态视图——类似视频，图片，或者相机视图——或者其他可以在全屏中受益的复杂任务，类似于编辑文档与照片。

NOTE：If you use the current context modal view style to display modal content within a split view pane, popover, or other view that isn’t fullscreen, you should switch to using a sheet when presenting modal content in a compact environment.

注释：如果你使用当前文本模态视图样式在分屏视图、弹出框或其他非全屏视图中去呈现模态内容，在这种紧凑的环境中显示模态视图时需要切换到列表。

Use modality when it makes sense. Create a modal experience only when it’s critical to focus people’s attention on making a choice or performing a task that’s different from their current task. A modal experience takes people out of their current context and requires an action to dismiss, so it’s essential to use it only when it provides a clear benefit.

当有意义时使用模态视图。仅当人们需要把注意力放在做出选择或完成与当前不同的任务时才创建模态体验，模态体验将人们带出当前的文本且需要操作才能取消，所以只有有明确的益处时才去使用（模态视图）。

Reserve alerts for delivering essential — and ideally actionable — information.Typically, an alert appears because something has gone wrong. Because an alert interrupts the experience and requires a tap to dismiss, it’s important for people to feel that the intrusion is warranted. For guidance, see Alerts.

保留警示框以传递必要且理论上可操作的信息。通常警示框的出现是因为某些事情存在运行错误，因为警示框会打搅体验且要求点击操作才能消除，重要的是确保让人们觉得这种闯入是必要的。

Keep modal tasks simple, short, and narrowly focused. Avoid creating an app within your app. If a modal task is too complex, people can lose sight of the task they suspended when they entered the modal context. Be especially wary of creating modal tasks that involve a hierarchy of views because people can get lost and forget how to retrace their steps. If a modal task must contain subviews, provide a single path through the hierarchy and a clear path to completion. Avoid using a Done button for anything other than completing the task.

保持模态视图的简单、简短和专注。避免在一个应用程序中又创造一个应用程序，如果模态任务太过复杂，人们在进入模态任务后会忽略（原本）暂停的任务，特别要注意涉及层级结构视图的模态任务创建，人们会迷失和忘记如何返回原先的步骤，如果一个模态任务必须包含子视图，提供单一且清晰的完成路径。

Always include a button that dismisses the modal view. For example, you might use Done or Cancel. Including a button ensures that the modal view is accessible to assistive technologies and provides an alternative to dismissal gestures.

总是包含一个能够取消模态视图的按钮。例如，你可能可以使用“完成”或者“取消”，包含一个确保辅助技术可以访问模态视图的按钮，并提供可供选择的取消手势。

译者注释

assistive technologies 是指Assistive Technology），任何能够增加、维持、改进或促进使用者的个人能力的项目、设备或产品系统。常见的产品包括眼镜、助听器、轮椅、拐杖、特制餐具、握笔器等。

在 iOS 系统设置的辅助功能中有一系列设置项用于增强使用者的个人能力，不局限于帮助残疾人。

When necessary, help people avoid data loss by getting confirmation before closing a modal view. Regardless of whether people use a dismiss gesture or a button to close the view, if the action could result in the loss of user-generated content, present an action sheet that explains the situation and gives people ways to resolve it.

必要的时候，在关闭模态视图前帮助人们确认从而避免数据丢失。无论人们是使用取消手势或按钮来关闭视图，如果该操作可能导致用户生成的内容丢失，请提供动作列表说明情况并给人们解决问题的方式。

Don’t display a card that appears on top of a popover. Although you can display a card within a popover, nothing should appear on top of a popover (except possibly an alert). In rare cases when you need to present a card after people take an action in a popover, close the popover before displaying the card.

不要在弹出框的上方呈现一个卡片。尽管你可以在弹出框之内显示一个卡片，但在弹出框顶部不应该显示任何内容（除了可能的警示框），在极少数情况下当人们在弹出框中进行操作后你需要呈现卡片，请在显示卡片之前关闭弹出框。

In general, display a title that identifies the modal task. When people enter a modal task, they switch away from their previous context, so it’s a good idea to make the new context clear. You might also provide text in other parts of the view that more fully describes the task or provides guidance.

总体上来说，显示模态任务的标题让用户确认(这是什么任务)，当人们进入一个模态任务时，他们会从之前的文本中离开，所以新文本需要表意清晰，你还可以在视图其他部分提供更全面的描述任务或提供指导的文本。

Coordinate the modal view appearance with your app. For example, when a modal view includes a navigation bar, it should use the same appearance as the navigation bar in your app.

将模态视图与应用程序外观相协调。例如，当一个模态视图包含导航栏时，它需要使用与应用程序中的导航栏相同的外观。

Choose a modal transition style that makes sense in your app. Use a transition style that coordinates with your app and enhances the awareness of the temporary context shift. The default transition vertically slides the modal view up from the bottom of the screen and back down when it’s dismissed. Use consistent modal transition styles throughout your app.For developer guidance, see UIViewController and UIPresentationController.

选择在应用程序中有意义的模态转换样式。使用一个与应用程序相协调的转换风格，并增强对暂时性语境转换的认识，默认(打开)模态视图的方式是从底部屏幕垂直向上滑动，在关闭时向下滑动，在应用程序中使用一致的模态转换样式。

片尾重点总结：

• 模态是临时展现内容的方式，需要操作（点击“完成”或“取消”按钮或向下滑动）才能取消。
• 在不复杂且非沉浸式内容使用列表的方式实现模态。
• 对于编辑文档、图片等沉浸式复杂内容时使用全屏的方式实现模态。
• 保持模态视图的简单、简短和专注，以免模态视图的出现导致用户忽略先前的操作。
• 总是包含一个能取消的模态视图的按钮。
• 模态视图外观与应用程序整体外观应该保持一致。
• 在应用程序中使用一致的模态视图转换样式。

为了让内容的关联性更强，我提前将 iOS 系统中的 4 种模态视图—— Activity Views,  Action Sheets,  Alerts 以及 Popover 内容进行翻译 ,便于我们对模态这个概念有更全面的理解，如下是 iOS 设计规范中关于这 4 种模态视图的译文。

• Action Sheets

动作列表

An action sheet is a specific style of alert that appears in response to a control or action, and presents a set of two or more choices related to the current context. Use an action sheet to let people initiate tasks, or to request confirmation before performing a potentially destructive operation. On smaller screens, an action sheet slides up from the bottom of the screen. On larger screens, an action sheet appears all at once as a popover.

动作列表是响应控件或操作的特定警示框样式，显示与当前文本相关的两个或多个选项，使用动作列表让人们启动任务，在执行潜在破坏性操作前请求确认，在更小的屏幕上，动作列表从屏幕底部向上滑动，在更大的屏幕上，操作列表作为弹出框的形式同时出现。

译者注释

在下文的 popover 部分的示例图所示，在 iPad 上是以弹出框的形式呈现的。

Provide a Cancel button if it adds clarity.  A Cancel button instills confidence when the user is abandoning a task. Cancel buttons should always be included in action sheets at the bottom of the screen.

如果增加了（逻辑上的）清晰度请提供一个取消按钮。当用户取消任务时取消按钮能够增强信心，取消按钮需要处于屏幕底部并总是包含在动作列表当中。

Make destructive choices prominent. Use red for buttons that perform destructive or dangerous actions, and display these buttons at the top of an action sheet.

做出具有突出破坏性的选择。按钮使用红色来表示破坏性与危险操作，并在动作列表顶部呈现这些按钮。

Avoid enabling scrolling in an action sheet. If an action sheet has too many options, people must scroll to see all of the choices. Scrolling requires extra time to make a choice and is hard to do without inadvertently tapping a button.

避免在动作列表中启用滚动。如果动作列表有太多选项，人们必须滚动来查看全部的选项，滚动就会要求额外的时间去做选择，且很难不误触其他按钮。

• Activity Views

An activity is a task, such as Copy, Favorite, or Find, that’s useful in the current context. Once initiated, an activity can perform a task immediately, or ask for more information before proceeding. Activities are managed by an activity view, which appears as a sheet or popover, depending on the device and orientation. Use activities to give people access to custom services or tasks your app can perform.

活动是类似于复制、收藏或查找等在当前的文本中有用的任务，一旦启动，活动就可以立刻执行任务或在继续之前询问更多信息，活动是由活动视图控制的，以列表或弹出框的形式出现，具体取决于设备和方向，使用活动可让人们执行自定义服务或应用程序可执行任务（类似于发送邮件，使用 Airdrop 等）。

The system provides a number of built-in activities, including Print, Message, and AirPlay. These tasks always appear first in activity views and can’t be reordered. You don’t need to create custom activities that perform these built-in tasks. Activity views also display share and action extensions from other apps. See Sharing and Actions.

系统提供了很多内置活动，包含打印、消息和 Airplay，这些任务总是首先出现在活动视图中且无法重新排序，你不需要创造一个自定义任务去执行这些系统内置任务。活动视图也呈现分享和来自其他应用程序的操作扩展。

Design simple template images to represent your custom activities. A template image uses a mask to create an icon. Use black and white with appropriate transparency and antialiasing, and don’t include a drop shadow. Template images should be centered in an area measuring about 70px × 70px.

设计简单的模板图像来表示您的自定义活动。模板图像使用遮罩（作为底层）创建图标，使用黑白色和适当的透明度并加入抗锯齿功能，但不加入阴影。模板图像应该居中于 70px × 70px 的区域。

Craft activity titles that succinctly describe your tasks. Titles appear below the icons in an activity view. Short titles work best. When a title is too long, iOS first shrinks the text and then—if the title is still too long—truncates it. In general, avoid including your company or product name in a title.

创建简洁描述任务的活动标题。标题显示在活动视图中的图标下方，短标题是最有效的。iOS 系统首先会缩小文本，（在缩小文本后）如果文本还是太长——可以将其截断。通常情况下，避免在标题文本中包含公司或产品名称。

Make sure activities are appropriate for the current context. Although system-provided tasks can’t be reordered in an activity, they can be excluded if they aren’t applicable to your app. For example, to prevent people from printing images, you can exclude the Print activity. You can also identify which custom tasks to show at any given time.

确保活动适合当前文本。即使系统提供的任务不能够在活动中被重新排序，如果他们不适用于你的应用程序可以将他们排除在外，例如，为了防止人们打印图片，你可以将打印活动排除在外，你还可以确定在任何给定的时间显示哪些自定义任务。

Use the Action button to display an activity view. People are accustomed to accessing system-provided activities when they tap the Action button. Avoid confusing people by providing an alternative way to do the same thing.

使用操作按钮展示活动视图。人们习惯于在点击操作按钮时访问系统提供的活动，避免通过提供另外一种方式去做同样的事情而让人们困惑。

For developer guidance, see UIActivityViewController and UIActivity.

• Alerts

Alerts convey important information related to the state of your app or the device, and often request feedback. An alert consists of a title, an optional message, one or more buttons, and optional text fields for gathering input. Aside from these configurable elements, the visual appearance of an alert is static and can’t be customized.

警示框传递与应用程序及设备状态相关的重要信息且通常要求反馈，警示框由标题、可选信息，一个或多个按钮和可选文本输入内容的文本框组成，除了这些可配置元素之外，警示框的视觉外观是静态的和不能被定制的。

Minimize alerts. Alerts disrupt the user experience and should only be used in important situations like confirming purchases and destructive actions (such as deletions), or notifying people about problems. The infrequency of alerts helps ensure that people take them seriously. Ensure that each alert offers critical information and useful choices.

最小化警示框使用。警示框中断了用户体验，所以应该在确认购买或破坏性操作(例如删除操作)或通知人们相关问题等重要情况下被使用，避免警示框的频繁出现能够确保人们对警示框的重视，确保每个警示框提供关键信息和有用选择。

Test the appearance of alerts in both orientations. An alert may appear differently in landscape mode and portrait mode. Optimize alert text so it reads well in any orientation without scrolling.

For developer guidance, see UIAlertController.

在两个方向测试警示框外表。在横向和纵向的方向上警示框显示的可能不同，优化警示框文本，从而在不滚动(屏幕)的前提下能够有较好的阅读体验。

Alert Titles and Messages

警示框标题和信息

Write short, descriptive, multiword alert titles. The less text people have to read onscreen, the better. Try to craft a title that avoids adding extra text as a message. Because single-word titles rarely provide useful information, consider asking a question or using short sentences. Whenever possible, keep titles to a single line. If the title is a complete sentence, use sentence-style capitalization and appropriate ending punctuation. If the title is a sentence fragment, use title-style capitalization and don’t add ending punctuation.

写简短、描述性的、多词的警示框标题。在屏幕上阅读的文本越少越好，尝试设计一个标题避免添加额外的文本作为信息，因为单词标题很少提供有用信息，考虑提问或使用简短句子的形式，只要有可能请将标题保持在一行，如果标题是完整的句子，使用句式大写和适当的结束标点，如果标题是句子片段，使用标题样式大写且不要添加结束标点。

If you must provide a message, write short, complete sentences. Try to keep messages short enough to fit on one or two lines to prevent scrolling. Use sentence-style capitalization and appropriate punctuation.

如果你必须提供一个消息，写简短、完整的句子。尽量保持信息足够短以容纳一到两行以防止滚动（屏幕），使用句式大写和适当的标点符号。

Avoid sounding accusatory, judgmental, or insulting. People know that alerts notify them about problems and dangerous situations. As long as you use a friendly tone, it’s better to be negative and direct than positive and oblique. Avoid pronouns such as you, your, me, and my, which are sometimes interpreted as insulting or patronizing.

避免听起来像职责、评判和侮辱。人们知道警示框会通知他们问题和危险情况，只要你使用友好的语气，最好是负面和直接的好过积极和间接的，避免代词像“你”、“你的”“我”和“我的”，这些代词有些时候会让人们觉得是侮辱性的或感觉高人一等的。

Avoid explaining the alert buttons. If your alert text and button titles are clear, there should be no need to explain what the buttons do. In rare cases where you must provide guidance, use the word tap, preserve capitalization when referencing buttons, and don’t enclose button titles in quotes.

避免解释警示框按钮。如果你的警示框文本和按钮表意是清楚的，那么不需要解释按钮的用途，在很少的情况下你必须提供指导，请使用“tap”这个文字，引用按钮时保持大写，不要将按钮标题括在引号里。

Alert Buttons

警示框按钮

Generally, use two-button alerts. Two-button alerts provide an easy choice between two alternatives. Single-button alerts inform, but give no control over the situation. Alerts with three or more buttons create complexity and can require scrolling, which is a bad user experience. If you find that you need more than two choices, consider using an action sheet instead. See Action Sheets.

通常情况下使用双按钮的警示框，两个按钮警示框在两个方向提供简单的选择，单按钮警示框可以通知，但无法控制局面，警示框有三个或更多按钮会造成复杂性和可能会要求滚动，这是一种更差的用户体验，如果你能够找到超过两种选择，考虑使用动作列表来代替。

Give alert buttons succinct, logical titles.The best button titles consist of one or two words that describe the result of selecting the button. As with all button titles, use title-style capitalization and no ending punctuation. To the extent possible, use verbs and verb phrases that relate directly to the alert title and message—for example, View All, Reply, or Ignore. Use OK for simple acceptance. Avoid using Yes and No.

给出简洁、合理的警示框标题，最好的按钮标题是由描述选择按钮结果的一到两个单词组成，与所有按钮标题一样，使用标题样式大写及无结束的标点符号，尽可能使用与警示框标题与信息直接相关的动词和动词短语——例如，查看全部，恢复，或忽略。使用 OK 作为简单的接收（信息），避免使用 Yes 和 No。

Place buttons where people expect them. In general, buttons people are most likely to tap should be on the right. Cancel buttons should always be on the left.

把按钮放在人们期望它在的地方。通常情况下，人们更希望点击的按钮应该在右侧，取消按钮通常应该在左侧。

Label cancellation buttons appropriately.A button that cancels an alert’s action should always be labeled Cancel.

恰当地标记取消按钮。取消警示框操作的按钮应该始终被标记为取消。

Identify destructive buttons. If an alert button results in a destructive action, such as deleting content, set the button’s style to Destructive so that it gets appropriate formatting by the system. For developer guidance, see the UIAlertActionStyleDestructive constant of UIAlertAction. Additionally, provide a Cancel button so people can safely opt out of the destructive action. Make the Cancel button bold by marking it as the default button.

确认破坏性按钮，如果一个警示框按钮导致破坏性操作，类似于删除内容，通过设置具有破坏性的按钮风格从而从系统获得合适的格式。此外，提供一个取消按钮这样人们可以安全地退出破坏性操作，将取消按钮标记为默认按钮设置，并将字体改为粗体，

Allow people to cancel alerts by exiting to the Home screen. Accessing the Home screen while an alert is visible exits the app. It should also produce the same effect as tapping the Cancel button—that is, the alert is dismissed without performing any action. If your alert doesn’t have a Cancel button, consider implementing a cancel action in your code that runs when someone exits your app.

允许人们通过退出主屏幕来取消警示框。在显示警示框的情况下访问主屏幕将退出应用程序，它应产生与点击取消按钮一样的效果——那就是警示框在没有进行任何操作的情况下被解除，如果你的警示框没有取消按钮，考虑在你的代码中实现取消按钮并在人们退出你的应用程序时运行。

• Popovers

A popover is a transient view that appears above other content onscreen when you tap a control or in an area. Typically, a popover includes an arrow pointing to the location from which it emerged. Popovers can be nonmodal or modal. A nonmodal popover is dismissed by tapping another part of the screen or a button on the popover. A modal popover is dismissed by tapping a Cancel or other button on the popover.

弹出框是当你点击控件或某个区域时出现在屏幕内容上方的临时视图。通常弹出框包含一个箭头指向它出现的位置，弹出框可以是模态或非模态的，非模态的弹出框通过点击屏幕的其他部分(除弹出框以外部分)或点击在弹出框中的按钮进行取消，模态视图通过点击取消按钮或在弹出框中的其他按钮进行取消。

Popovers are most appropriate on larger screens and can contain any variety of elements, including navigation bars, toolbars, tab bars, tables, collections, images, maps, and custom views. When a popover is visible, interactions with other views are normally disabled until the popover is dismissed. Use a popover to show options or information related to the content onscreen. Many iPad apps, for example, show a popover of sharing options when you tap the Action button.

弹出框最适合在更大的屏幕上使用，可以包含各种类型的元素，包括导航栏、工具栏、标签栏、选项卡栏、表格、集合、图像、地图和定制视图，当一个弹出框是可见的情况下，通常会禁用与其他视图的交互直到弹出框被取消，使用弹出框在屏幕上显示与内容相关的选项或信息。例如，在很多 iPad 应用程序中当你点击一个操作按钮时展示包含分享选项的弹出窗口。

Avoid displaying popovers on iPhones. Generally, popovers should be reserved for use in iPad apps. In iPhone apps, utilize all available screen space by presenting information in a full-screen modal view, rather than in a popover. For related guidance, see Modality.

避免在 iPhone 上显示弹出框，通常情况下，弹出框应该保留在 iPad 应用程序上使用，在 iPhone 应用程序中，利用所有可用的屏幕空间，以全屏模式显示信息，而不是弹出框。

Use a Close button for confirmation and guidance only. A Close button, such as Cancel or Done, is worth including if it provides clarity, such as exiting with or without saving changes. In general, a popover should close automatically when its presence is no longer necessary. In most cases, a popover should close when someone taps outside of its bounds or selects an item in the popover. If multiple selections can be made, the popover should remain open until someone explicitly dismisses it or taps outside of its bounds.

使用关闭按钮仅用于确认和指导，关闭按钮，类似于取消按钮和完成按钮值得包括它是否提供了清晰性（退出时是否保存更改），通常情况下当不再需要弹出框时应自动关闭，在大多数情况下，一个弹出框需要关闭，当有人在弹出框之外点击或选择某个在弹出框选项时，弹出框应该关闭，如果能够做出很多选择，弹出框窗口应该一直保持显示的状态，直到人们明确的取消或点击弹出框以外的区域时。

Always save work when automatically closing a nonmodal popover. It’s easy to dismiss a nonmodal popover unintentionally by tapping another part of the screen. Discard work only when someone taps an explicit Cancel button.

当自动关闭非模态弹出框时总是保存工作内容，当点击屏幕的其他部分时会无意的忽略非模态弹出框，当人们明确地点击取消按钮时才放弃工作。

Position popovers appropriately onscreen. A popover’s arrow should point as directly as possible to the element that revealed it. Because popovers can’t be dragged around the screen, a popover shouldn’t cover essential content people may need to see while using the popover. A popover also shouldn’t cover the element that was tapped to show the popover.

在屏幕上适当放置弹出窗口，一个弹出窗口的箭头应该尽可能直接指向显示他的元素，因为弹出框不能在屏幕上被拖动，一个弹出框不应该覆盖人们在使用弹出框窗口时可能要查看的元素，一个弹出框也不应该覆盖用来显示弹出框的按钮（或控件）。

Show one popover at a time. Displaying multiple popovers clutters the interface and causes confusion. Never show a cascade or hierarchy of popovers, in which one emerges from another. If you need to show a new popover, close the open one first.

一次显示一个弹出框。呈现多弹出框会堆满界面并造成困惑，永远不要显示一个层次或多层级的弹出框，其中从一个到另一个出现，如果你需要展示一个新的弹出框，先关闭前一个打开的弹出框。

Don’t show another view over a popover. Except for an alert, nothing should be displayed on top of a popover.

不要在弹出框之上显示其他视图，除警示框之外，没有什么内容化需要在弹出框之上呈现。

1. When possible, let users close one popover and open another with a single tap.Avoiding extra taps is especially desirable when several different bar buttons each open a popover.

当可能的时候，让用户关闭一个弹出框和用一次点击打开另一个(弹出框)，当每个不同的栏按钮都对应一个弹出框时，避免额外的点击是尤其可取的。

Avoid making a popover too big. A popover shouldn’t take over the entire screen. Make it only big enough to display its contents and point to the place it came from. Be aware that the system might adjust the size of a popover to ensure it fits well onscreen.

避免弹出框太大，一个弹出框不应该占据整个屏幕，让弹出框能够呈现内容并指向它的出处即可，注意系统可能会调整弹出框大小确保弹出框大小在屏幕上很适合。

Make sure custom popovers look like popovers. Although you can customize many of the visual aspects of a popover, avoid creating a design people might not recognize as a popover. Popovers tend to work best when they contain standard controls and views.

确保自定义弹出框看起来像弹出框，尽管你可以定义弹出框的很多方面，避免创造一个人们无法识别为弹出框的设计，当弹出窗口包含标准控件和视图时能够工作的最好。

Provide a smooth transition when changing the size of a popover. Some popovers provide both condensed and expanded views of the same information. If you adjust the size of a popover, animate the change to avoid giving the impression that a new popover replaced the old one.

在改变弹出框大小时提供一个顺滑的转换，一些弹出框对同样的信息提供了精简视图和详细视图，如果调整弹出框的大小请设置转变的动画，以免让人们以为新的弹出框代替了旧的弹出框。(前后没有关联。)

未完待续，下一篇《App Architecture_Navigation》，敬请期待。

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