Many apps allow people to shake the device to undo and redo certain operations, such as typing or deleting. When initiated in this manner, an alert asks the user to confirm or cancel the undo or redo operation.
大多数应用允许用户以晃动设备来取消或重做某些操作，如输入或删除. 当触发这个模式，会有一个弹出框要求用户确定或取消这个取消或重做操作.
Briefly and precisely describe the operation to be undone or redone.The undo and redo alert title automatically includes a prefix of “Undo ” or “Redo ” (including the trailing space). You need to provide an additional word or two that describe what’s being undone or redone, to appear after this prefix. For example, you might create alert titles such as “Undo Name” or “Redo Address Change.”
简要准确的描述这个操作将被取消或重做。这个取消和重做弹出框标题自动包含“取消”或“重做”前缀（包含尾随空格）。在前缀之后，你需要提供额外的描述说明什么将被取消或重做。例，你可以创建“取消命名”或“重做地址变更”类似弹出框标题。
If you use the shake gesture for undo and redo, don’t use it for other actions.Although you can programmatically give multiple meanings to the shake gesture, you run the risk of confusing people and making your app unpredictable.
如果你使用摇晃手势来取消或重做，则不要用它来做其他操作。虽然你能给摇晃手势编程序为多种意义，但这会产生用户混乱和应用不可预测的风险。
Provide undo and redo buttons sparingly.It’s confusing when apps provide multiple ways to perform the same task. If your app truly warrants dedicated undo and redo buttons, use the standard system-provided icons and put them in an expected location, such as a navigation bar.
保守的提供取消和重做按钮.当应用提供多种方式来执行一样的任务是会引起混淆. 如果你的应用确实有正当理由专门用取消和重做按钮，使用系统提供的标准图标并放置在预期的位置，比如导航栏。
Perform undo and redo operations in the current context only.Undo and redo should have a clear and immediate effect on the current context, not an earlier one.
仅在当前情景使用取消和重做操作。并应该在当前的场合下有一个清楚且及时的响应，而不是较早期的。
For implementation details, seeUndo Architecture.
更多实现细节，参阅 UndoArchitecture.
