辅助功能:
http://useyourloaf.com/blog/2012/04/23/voiceover-accessibility.html
http://mattgemmell.com/accessibility-for-iphone-and-ipad-apps/
最详细的,当然还是官网了
https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/iPhoneAccessibility/Accessibility_on_iPhone/Accessibility_on_iPhone.html
