转载自－Apple 官网，感觉不错，记录之 （https://developer.apple.com/design/tips/）
Some useful design tips about IOS.
Make it easy for people to interact with content and controls by giving each interactive element ample spacing. Give tappable controls a hit target of about 44 x 44 points.
Hit Targets
Create controls that measure at least 44 points x 44 points so they can be accurately tapped with a finger.
Formatting Content
Create a layout that fits the screen of an iOS device. Users should see primary content without zooming or scrolling horizontally.
Touch Controls
Use UI elements that are designed for touch gestures to make interaction with your app feel easy and natural.
Text Size
Text should be at least 11 points so it's legible at a typical viewing distance without zooming.
Contrast
Make sure there is ample contrast between the font color and the background so text is legible.
Spacing
Don't let text overlap. Improve legibility by increasing line height or letter spacing.
High Resolution
Provide high-resolution versions of all image assets. Images that are not @2x and @3x will appear blurry on the Retina display.
Distortion
Always display images at their intended aspect ratio to avoid distortion.
Organization
Create an easy-to-read layout that puts controls close to the content they modify.
Alignment
Align text, images, and buttons to show users how information is related.