iOS8 Human Interface Guidelines 精选阅读（中英对照）
用了两个星期时间断断续续读完iOS的guidelines英文原版，原文是写得有点啰嗦，所以精选了以下觉得比较重要的点，并加以自己的解释；当然如果你有时间，还是推荐阅读英文原文。首先是因为翻译的版本基本是不全的、旧的，就像ISUX的翻译的对比原文就会发现中间省略了好多。本文的作用并不像多数的翻译那样，让你粗略地了解里面的内容，而是精选出一些点使你体会到苹果的设计思想。 我读guidelines的目的不仅仅是要看他们是怎样规定的，而是要看他们为什么这样规定，在了解了制定规则背后的原因之后不仅便于记忆规则本身，还能了解苹果的设计思路，当吸收了设计思路之后，就不再是墨守成规，而是更自信和灵活地运用规则，甚至创造属于自己的规则。就像tweetie发明下拉刷新手势之后苹果反而把这种手势加进了自己的guidelines。 读英文原版还有一个显然易见的好处就是熟悉专业英语表达，guildlines的措辞显得优美而精确，值得去读读。
完整读完后，觉得苹果的设计思路是很严谨的User-Centered。经常会出现的一个词是gratuitous （adj. 无理由的），告诫要避免无理由的设计。解释一项规定时，常常告诉读者如果你不这样做用户会觉得怎么样，然后产生什么行为，最终导致什么不好的结果；相反按照规则则用户感觉良好，最终导向好的结果。逻辑链条是：设计决定–用户感受–用户行为–设计效果。这可以说是交互设计的基本思考方式，充分分析人机之间的相互作用。我发现很多的设计初学者（包括我自己）经常会范一个错误，就是机械的运用各种设计原则和盲目崇拜大公司的设计，只要自己的设计能在某书的设计原则里找到或者与某知名的产品里一样，那就觉得是OK的。有这想法就是因为还没有了解别人为什么这样定原则的，或为什么这样设计的。这种做法在Guidelines里面的词句形容就是slavish copy。不止是设计，对待任何事情都不应该“认死理”或“跟大流”，因为这是一种思维上的懒惰，或是盲目的理论自信。不经过思考的理论用来装装逼还是可以的，真正要做设计时这种死理论会害死一个产品。真正的科学家是谦逊的，因为他们坦然接受未知，随时准备着推翻自己之前建立的理论，而不是死死抱住自己的理论盲目自信。
Translucent elements—such as Control Center—provide context, help users see that more content is available, and cansignal transience.
Windows 7 Aero
iOS运用半透明效果的理由是表明本窗口是“暂时 transience”的，所以你可以看见几乎所有浮层都是半透明的，所以设计时应该避免一个需要用户长时间停留的窗口使用半透明。另外Guidelines里没提到的作用是增加空间感，表明了本窗口是叠加在其他窗口是上的。扁平化的设计下视觉上不能再采用大面积的阴影表明空间纵深感，所以使用半透明的手法来代替。相比之下，WP倾向于完全摒弃纵深感，而Android Material Design则保留了阴影，这比iOS的半透明手法看起来更重一些，但优点是显示更清晰。iOS的米纸效果个人觉得更女性化而Android显得阳刚气一点，这也符合硬件的气质。界面之所以要显示纵深感，是要告诉用户界面的主次层级关系，浮沉是次要而暂时的，浮沉之后才是承载主要任务的界面。但Win7的Aero效果的纵深感却不是出于这一目的，而是用于区分窗口和表示当前正在使用的窗口。
Use plenty of negative space.Negative space makes important content and functionality more noticeable and easier to understand. Negative space can also impart a sense of calm and tranquility, and it can make an app look more focused and efficient.
When users select a month, the year view zooms in and reveals the month view.Today’s date remains highlighted and the year appears in the back button,so users know exactly where they are, where they came from, and how to get back.
A similar transition happens when users select a day: The month view appears to split apart, pushing the current week to the top of the screen and revealing the hourly view of the selected day. With each transition,Calendar reinforces the hierarchicalrelationship between years, months, and days.
Make it easy to focus on the main task by elevating important content or functionality.Some good ways to do this are to place principal items in the upper half of the screen and—in left-to-right cultures—near the left side of the screen:
Use alignment to ease scanning and communicate groupings or hierarchy.Alignment tends to make an app look neat and organized and it gives users places to focus while they scroll through screenfuls of information. Indentation and alignment of different information groups indicate how the groups are related and make it easier for users to find specific items.
As much as possible, avoid inconsistent appearances in your UI.In general, elements that have similar functions should also look similar.People often assume that there must be a reason for the inconsistencies they notice, and they’re apt to spend time trying to figure it out.
As much as possible, avoid displaying a splash screen or other startup experience.It’s best when users can begin using your app immediately.
尽量避免splash screen（欢迎页），建议使用Launch Image来代替，意思是制造一张与首界面相似的静态图片。当用户开启app时先显示这张图，等系统准备就绪后切换到首屏。给用户应用启动很迅速的假象。国内就算是知名的企业也很多违反这原则。
Avoid asking people to supply setup information.Instead:
Focus on the needs of 80 percent of your users.When you do this, most people won’t have to supply any settings, because the app is already set up to behave the way they expect. If there is functionality that only a few users might want—or that most users might want only once—leave it out.
Get as much information as possible from other sources.If you can use any of the information people supply in built-in app or device settings, query the system for these values; don’t ask people to enter them again.
If you must ask for setup information, prompt people to enter it within your app.Then, store this information as soon as possible (potentially, in your app’s settings). This way, people aren’t forced to switch to Settings before they get the chance to enjoy your app. If people need to make changes to this information later, they can go to the app’s settings at any time.
Delay a login requirement for as long as possible.It’s best when users can navigate through much of your app and use some of its functionality without logging in. For example, App Store doesn’t ask users to log in until they decide to buy something. Users often abandon apps that force them to log in before they can do anything useful.
If users must log in, display in the login view a brief, friendly explanation that describes the reasons for the requirement and how it benefits users.
Think carefully before providing an onboarding experience
Give users only the information they need to get started.A good onboarding experience shows users what to do first or briefly demonstrates a few of the features that most users are interested in. If you give too much information to users before they have a chance to explore your app, you make users responsible for remembering details they don’t need right away and you may send the message that your app is hard to use.If additional help is needed for specific tasks, provide that help only when the user is performing those tasks.
Never quit an iOS app programmatically.People tend to interpret this as a crash. If something prevents your app from functioning as intended, you need to tell users about the situation and explain what they can do about it. Here are two good ways to do this:
If all app features are unavailable, display a screen that describes the situation and suggests a correction.The information gives feedback to users and reassures them that there’s nothing wrong with your app. It also puts users in control, letting them decide whether they want to take corrective action and continue using your app or switch to another app.
If only some app features are unavailable, display either a screen or an alert when people try to use the feature.Otherwise, people should be able to use the rest of the app. If you decide to use an alert, be sure to display itonlywhen people try to access the feature that isn’t functioning.
Broadly speaking, there are three main styles of navigation, each of which is well suited to a specific app structure:
Content- or experience-driven
In general, it’s best to give users one path to each screen.If there’s one screen that users need to see in more than one context, consider using a temporary view,such as a modal view, action sheet, or alert.
Modality—that is, a mode in which something exists or is experienced—has advantages and disadvantages. It can give users a way to complete a task or get information without distractions, but it does so by temporarily preventing them from interacting with the rest of the app.
Always provide an obvious and safe way to exit a modal task.People should always be able to predict the fate of their work when they dismiss a modal view.
In a content area, add a button border or background only if necessary.Buttons in bars, action sheets, and alerts don’t need borders because users know that most of the items in these areas are interactive. In a content area, on the other hand, a button might need a border or a background to distinguish it from the rest of the content.
ShakeTo initiate an undo or redo action.
Touch and holdIn editable or selectable text, to display a magnified view for cursor positioning.
Double tapTo zoom in and center a block of content or an image.
To zoom out (if already zoomed in).
Feedbackhelps users know what an app is doing, discover what they can do next, and understand the results of their actions. UIKit controls and views provide many kinds of feedback.
Avoid unnecessary alerts.An alert is a powerful feedback mechanism, but it should be used only to deliver important—and ideally actionable—information. If users see too many alerts that don’t contain essential information, they quickly learn to ignore all alerts. To learn more about using an alert.
Make it easy for users to make choices. For example,you can use a picker or a table view instead of a text field, because most people find it easier to select an item from a list than to type words.
Balance a request for input by giving users something useful in return.A sense of give and take helps people feel they’re making progress as they move through your app.
Don’t take space away from the content people care about. For example, displaying a second, persistent bar at the top of the screen that does nothing but display brand assets means that there’s less room for content. Instead, defer to the user’s content and consider less intrusive ways to display pervasive branding, such asusing a custom tint or font, or subtly customizing the background of a screen.
Resist the temptation to display your logo throughout the app.Mobile device screens are relatively small, and every occurrence of a logo takes space away from the content that users want to see. What’s more, displaying a logo in an app doesn’t serve the same purpose as displaying it in a webpage: It’s common for users to arrive on a webpage without knowing its owner, but it’s much less likely that users will open an iOS app without seeing its app icon.
To get this ratio, use an online contrast ratio calculator or you can perform the calculation yourself using the formula established in the WCAG 2.0 standard.Ideally the color contrast ratio in your app is 4.5:1 or higher.
Consider choosing a key color to indicate interactivity and state.Key colors in the built-in apps include yellow in Notes and red in Calendar. If you define a key color to indicate interactivity and state, make sure that the other colors in your app don’t compete with it.
Interactivity可交互性（在About Face里面称为Pliancy受范性）指一个平面的元素是否可交互的。iOS8、Android L和WP里面都各有一套自己的显示可交互性的方法，这很有趣。iOS6以前苹果用突起的物理隐喻显示按钮的可交互性；iOS7以后改为使用颜色，上文就是说应用需要有一个主色调来显示可交互性，如果按钮实在在背景底下不突出才考虑加边框或者加背景色；Android Kitkat之前是用色块和轻微的阴影做按钮的，Android L很大胆地采用字体来显示按钮可交互性，只要采用全大写的中线体，就算不加颜色也可以是按钮，当然也有有底色色块的按钮；WP则使用直角方形的边框显示按钮。
Text should never be smaller than 11 points, even when the user chooses the extra-small text size. For comparison, the body style uses a font size of 17 points at the large size, which is the default text-size setting.
To help you decide whether to use text or icons in the navigation bar or toolbar in your app, consider how many icons are visible onscreen at one time.Too many icons on a screen can make an app seem difficult to decode.
Remember that users are likely to read the text in your UI many times, andwhat might seem clever at first can become irritating when repeated.
If necessary, help users go directly to your app’s settings in Settings.In particular, if you display a message that describes where to find your settings, such as “Go to Settings > MyApp > Privacy > Location Services,” replace the description with a button that opens that location in Settings.
Aesthetic integrity doesn’t measure the beauty of an app’s artwork or characterize its style; rather, it represents how well an app’s appearance and behavior integrates with its function to send a coherent message.
Consistency lets people transfer their knowledge and skills from one part of an app’s UI to another and from one app to another app.
Feedback acknowledges people’s actions, shows them the results, and updates them on the progress of their task.
Sound can also give people useful feedback, but it shouldn’t be the only feedback mechanismbecause people can’t always hear their devices.
When virtual objects and actions in an app are metaphors for familiar experiences—whether these experiences arerooted in the real world or the digital world—users quickly grasp how to use the app.
People—not apps—should initiate and control actions. An app can suggest a course of action or warn about dangerous consequences, but it’s usually a mistake for the app to take decision-making away from the user. The best apps find the correct balance between giving people the capabilities they need while helping them avoid unwanted outcomes.
People expect to have ample opportunity to cancel an operation before it begins, and they expect to get a chance to confirm their intention to perform a potentially destructive action. Finally, people expect to be able to gracefully stop an operation that’s underway.
Define Your App
Now you can craft your app definition statement, concretely summarizingwhat the app does and for whom.A good app definition statement for this grocery-shopping app might be:
“A shopping list creation tool for thrifty people who love to cook.“
The best iOS apps balance UI customization with clarity of purpose and ease of use.
Be internally consistent.The more custom your UI is, the more important it is for the appearance and behavior of your custom elements to be consistent within your app. If users take the time to learn how to use the unfamiliar controls you create, they expect to be able to rely on that knowledge throughout your app.
If titling a navigation bar seems redundant, you can leave the title empty. For example, Notes doesn’t title the current note because the first line of content supplies all the context users need.
Consider putting a segmented control in a navigation bar at the top level of an app.This is especially useful if doing so helps to flatten your information hierarchy, making it easier for people to find what they’re looking for. If you use a segmented control in a navigation bar, be sure to choose accurate back-button titles.
Use a navigation bar to enable navigation among different views and—if appropriate—to provide a control that manages the items in a view.If you need to provide a larger set of controls and you don’t need to enable navigation, consider using a toolbar instead
Consider using a segmented control to provide access to different perspectives or modes in the current context. It’s not a good idea to use a segmented control in a toolbar to show app-level tasks or modes, becausea toolbar is specific to the current screen or view. If you need to give people access to primary tasks, views, or modes in your app, use a tab bar instead.
segmented control不能放在toolbar里，因为会与tab bar混淆。tab bar用于整个app的首级导航，而segment control更多是当前页面、任务、视图的导航，多为二级导航。
Use icons if you need to put more than three items in a toolbar.Because text-titled buttons typically use more space than icons, it can be difficult to keep the titles from running together.
3 Kinds of Popover
1.Provides options that affect the main view, but doesn’t implement an inspector
Close the popover as soon as people make a choice or when they tap anywhere outside its bounds, including the control that reveals the popover.
2. Implements an inspector
Close the popover when people tap anywhere outside its bounds, including the control that reveals the popover.
In this scenario, don’t close the popover as soon as people make a choice, because they might want to make an additional choice or change the attributes of the current choice.
3. Enables a task
Close the popover when people complete or cancel the task by tapping a button in the popover, such as Done or Cancel.
In this scenario, you may not want to close the popover when people tap outside its borders, because it might be important that people finish—or explicitly abandon—the task. Otherwise, save people’s input when they tap outside a popover’s borders, just as you would if they tapped Done.
In general, save users’ work when they tap outside a popover’s borders. Not every popover requires an explicit dismissal, so people might dismiss them mistakenly.Discard the work people do in a popover only if they tap a Cancel button.
Be cautious if you change a popover’s size while it remains visible. You might want to change a popover’s size if you use it to display both a minimal and an expanded view of the same information. When you adjust the size of a visible popover,it’s usually a good idea to animate the change because it avoids giving the impression that a new popover has replaced the old one.
In general, display only one scroll view at a time.People often make large swipe gestures when they scroll, so it can be difficult for them to avoid interacting with a neighboring scroll view on the same screen.If you decide to put two scroll views on one screen, consider allowing them to scroll in different directions so that one gesture is less likely to scroll both views.For example, Stocks in portrait orientation on iPhone displays stock quotes in a vertically scrolling view above company-specific information, which is in a horizontally scrolling view.
Avoid displaying a navigation bar in both panes at the same time.Doing this would make it very difficult for users to discern the relationship between the two panes.
Give people alternative ways to access the primary pane, if appropriate.By default, only the secondary pane is displayed in a horizontally compact environment and you provide users with a button (typically located in a navigation bar) to reveal and hide the primary pane. The split view controller also supports the swipe gesture to perform the reveal/hide action. Unless your app uses the swipe gesture to perform other functions, you should let people swipe to access the primary pane.
Horizontally compact environment（狭小横屏）时，主窗格是隐藏的。可用左上角的按钮或是滑动手势调出。
In both styles, a table row becomes highlighted briefly when a user taps a selectable item. If a row selection results in navigation to a new screen, the selected row becomes highlighted briefly as the new screen slides into place.When the user navigates back to the previous screen, the originally selected row again becomes highlighted briefly to remind the user of the earlier selection(it doesn’t remain highlighted).
If table content is extensive or complex, avoid waiting until all the data is available before displaying anything. Instead,fill the onscreen rows with textual data immediately and display more complex data—such as images—as they become available.This technique gives users useful information right away and increases the perceived responsiveness of your app.
Consider displaying “stale” data while waiting for new data to arrive.Although this technique isn’t recommended for apps that handle frequently changing data, it can help more static apps give users something useful right away. Before you decide to do this, gauge how often the data changes and how much users depend on seeing fresh data quickly.
As much as possible, display a date picker inline with the content.It’s best when users can avoid navigating to a different view to use a date picker. In a horizontally regular environment, a date picker can appear within a popover or inline with content.
Use a page control when it’s more important to show users how many views are open than it is to help them choose a specific view.
Page Control（页面指示器）的作用是指示有多少项目可以显示，但项目数目比快速选择某一项更重要时，就用Page Control；反之用列表。
In general, use a picker when users are familiar with the entire set of values. Because many of the values are hidden when the wheel is stationary,it’s best when users can predict what the values are. If you need to provide a large set of choices that aren’t well known to your users, a picker might not be the appropriate control.
Consider using a table view, instead of a picker,if you need to display a very large number of values. This is because the greater height of a table view makes scrolling faster.
Use a stepper when users might need to make small adjustments to a value.
Use a verb or verb phrase to describe the action the button performs.An action-specific title shows users that the button is interactive and tells them what will happen when they tap it.
Asks for confirmation of user-initiated tasks, do not use Alert, use Action Sheet instead.
Title-style capitalizationmeans that every word is capitalized, except articles, coordinating conjunctions, and prepositions of four or fewer letters when they aren’t the first word.
Sentence-style capitalizationmeans that the first word is capitalized, and the rest of the words are lowercase unless they are proper nouns or proper adjectives.
Avoid sounding accusatory or judgmental when you need to deliver negative news. People understand that many alerts tell them about problems or warn them about dangerous situations.As long as you use a friendly tone, it’s better to be negative and direct than it is to be positive but oblique.
As much as possible, avoid “you,” “your,” “me,” and “my.”Sometimes, text that identifies people directly can be ambiguous and can even be interpreted as insulting or patronizing.
Place buttons appropriately. Ideally, the button that’s most natural to tap should meet two criteria:It should perform the action that users are most likely to want and it should be the least likely to cause problems if a user taps it inadvertently.Specifically:
When the most likely button performs a nondestructive action, it should be on the right in a two-button alert. The button that cancels this action should be on the left.
When the most likely button performs a destructive action, it should be on the left in a two-button alert. The button that cancels this action should be on the right.
Pressing the Home button while an alert is visible should quit the app, as expected.Doing so should also be identical to tapping the Cancel button—that is, the alert is dismissed and the action isn’t performed.
Use an action sheet to:
Provide alternative ways to complete a task. An action sheet lets you to provide a range of choices that make sense in the context of the current task, without giving these choices a permanent place in the UI.
Get confirmation before completing a potentially dangerous task. An action sheet prompts users to think about the potentially dangerous effects of the step they’re about to take and gives them some alternatives.
Use a modal view when you need to offer the ability to accomplish a self-contained task related to your app’s primary function. A modal view is especially appropriate fora multistep subtask that requires UI elements that don’t belong in the main app UI all the time.
Transition Style of Model View
Vertical. In the vertical style, the modal view slides up from the bottom edge of the screen and slides back down when dismissed (this is the default transition style).
Flip. In the flip style, the current view flips horizontally from right to left to reveal the modal view. Visually, the modal view looks as if it is the back of the current view. When the modal view is dismissed, it flips horizontally from left to right, revealing the previous view.
模态的出现方式： 1.由下至上出现，由上至下消失；2. 翻转背后出现
Create an abstract interpretation of your app’s main idea.It rarely works well to use a photo or screenshot in an app icon because photographic details can be very hard to see at small sizes. Typically, it’s better to interpret reality in an artistic way, because doing so lets you emphasize the aspects of the subject that you want users to notice.
If the background of your icon is white, don’t add a gray overlay in an effort to increase its visibility in Settings. iOS adds a 1-pixel border stroke so that all icons look good on the white background of Settings.
Bar Button Icon
To ensure that all icons have a consistent perceived size, you may have to create some icons at different actual sizes.For example, the set of system provided icons shown here all have the same perceived size, even though the Favorites and Voicemail icons are actually a bit larger than the other three icons.