前一篇：iOS 8人機交互指南（7）
8. 動畫（Animation）
Beautiful, subtle animation pervades the iOS UI and makes the app experience more engaging and dynamic. Appropriate animation can:
（1）Communicate status and provide feedback
（2）Enhance the sense of direct manipulation
（3）Help people visualize the results of their actions
優美、巧妙的動畫遍布 iOS UI 的各處，使得 app 的用戶體驗更迷人、動感。恰當的動畫可以：
（1）顯示狀態、提供反饋；
（2）加強直接操作感；
（3）幫助人們將操作結果可視化。
Add animation cautiously, especially in apps that don’t provide an immersive experience.?Animation that seems excessive or gratuitous can obstruct app flow, decrease performance, and distract users from their task.
In particular, use motion effects and UIKit dynamic behaviors with purpose and restraint, and be sure to test the results. Used appropriately, these effects can increase users’ understanding and enjoyment; overusing them can make an app seem disorienting and difficult to control.
慎重考慮添加動畫，尤其是在 app 并沒有提供擬真體驗的時候。過度或不必要的動畫會阻礙 app 的流程，降低性能，轉移用戶對任務的注意力。
特別注意，要帶有目的或限制來使用手勢效果和 UIKit 動態行為，而且一定要驗證這些效果。恰當的使用這些效果可以增加用戶的理解力和愉悅感；過度的使用則會讓 app 看上去迷失方向、很難控制。
When appropriate, make custom animation consistent with built-in animation.?People are accustomed to the subtle animation used in the built-in iOS apps. In fact, people tend to regard the smooth transitions between views, the fluid response to changes in device orientation, and the physics-based scrolling as an expected part of the iOS experience. Unless you’re creating an app that enables an immersive experience—such as a game—custom animation should be comparable to the built-in animations.
適當地考慮讓自定義動畫與內置動畫保持一致。用戶已經習慣于 iOS app 中內置的那些巧妙動畫。事實上，用戶傾向于將視圖間的流暢切換、設備方向改變時的流暢響應、基于物理的滾動看做是 iOS 體驗的一部分。除非正在開發一款擬真體驗的 app ——例如游戲——否則自定義動畫還是應當同內置動畫保持一致。
Use animation consistently throughout your app.?As with other types of customization, it’s important to use custom animation consistently so that users can build on the experience they gain as they use your app.
在 app 中使用一致的動畫。與其他的自定義類型一樣，保持自定義動畫的一致性非常重要，這樣用戶可以隨著對 app 的使用建立起他們的使用體驗。
In general, strive for realism and credibility in custom animation.?People tend to be willing to accept artistic license in appearance, but they can feel disoriented when they experience movement that doesn’t make sense or appears to defy physical laws. For example, if you reveal a view by sliding it down from the top of the screen, you should dismiss it by sliding it back up because doing so helps users remember where the view comes from. If you dismiss the same view by sliding it down beyond the bottom of the screen, you break the user’s mental model of a view that’s available above the top of the screen.
通常情況下，要爭取自定義動畫現實可靠。用戶傾向于愿意接受外觀上充滿美感的協議，但當動作體驗無意義或看上去違背物理規則時他們會感到迷失方向。例如，如果你從屏幕頂部向下滑動來顯示視圖，那如果讓它消失的話就需要反向滑動，因為這樣做會讓用戶記住視圖來自哪里。如果在屏幕底部向下滑動該視圖來讓它消失，那就破壞了用戶對視圖的心理模型。
后一篇：iOS 8人機交互指南（9）
