Accessibility
iOS offers extensive accessibility features for users with vision loss, hearing loss, and other disabilities. Most UIKit-based apps can be made accessible with very little effort, allowing more people to use your app while providing an equally engaging experience for all.
iOS为用户提供大量可访问性的特性，如失明，失聪，或者其他残疾。大部分基于UIKit的app用少量的努力就能支持可访问性，当你为所有人提供同样迷人的体验时，会有更多用户愿意用你的app
Provide alternative text labels for images, icons, and interface elements.Alternative text labels aren’t visible onscreen, but they let VoiceOver audibly describe what's onscreen, making navigation easier for people with visual impairments.
为图片，图标，界面元素提供可选的文本标签。可选的文本标签在屏幕上不是可见的，但是让它们可听见从而知道什么在屏幕上，对于有视觉障碍的人是更好的导航。
Respond to accessibility preferences.If your app uses UIKit to implement its user interface, text and interface elements automatically adapt to certain accessibility preferences, such as bold and larger text. Your app should also check and respond to accessibility preferences when appropriate, such as when the option to reduce motion is enabled. Apps implementing custom fonts should attempt to match the accessibility behavior of the system fonts.
对可访问性偏好应答。如果你的app用UIKit来实现用户界面，文本和界面元素自动适应某一可访问性偏好，例如加粗或更大的文本。你的app应该也适当地检测和应答可访问性偏好，例如激动减少动作选项时。Apps实现自定义字体应该尝试匹配系统字体的可访问性。
Test your app with accessibility features.In addition to text and motion changes, accessibility options can change contrast, invert colors, reduce transparency, and more. Enable these settings and observe how your app will look and behave for people who enable these features.
测试你的app的可访问性特性。除了文本和动作的改变，可访问性选项还可以改变对比，调整颜色，减少透明度，及其他。激活这些设置然后作为用户观察你的app外观和行为。
Include closed captions and audio descriptions.Closed captions allow the deaf and hard-of-hearing to perceive spoken dialogue and other audible content in videos. Audio descriptions provide spoken narration of important video content for the visually impaired.
加入字幕和语音描述。字幕让聋子和听力障碍的人理解在视频文件中的口语对话和其他语音内容。语音描述为那些有视觉障碍的人提供重要视频文件内容的口语描述。
For more information, seeiOS AccessibilityandAccessibility Programming Guide for iOS.
https://developer.apple.com/ios/human-interface-guidelines/interaction/accessibility/
