Undo and Redo
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app允许用户摇动设备来撤销和重做一些操作，例如输入或者取消。当启动这种方式，一个提醒要求用户确认或取消撤销或重做操作。
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.”
简短和准确描述要撤销或重做的操作。撤销和重做提醒标题自动包括“Undo ” or “Redo ”的前缀（英文包括后面的空格）。你需要提供额外文字描述什么正在被撤销或重做，在这个前缀之后出现。例如，你也许创造提醒标题例如“Undo Name” or “Redo Address Change.”
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.
如果你使用摇动手势来做撤销和重做，不要用它做其他动作。尽管你可以利用编程给予摇动手势很多意义，这样会造成用户困惑和让你的app不可预测。
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.
保守地提供撤销和重做按钮。提供执行同样任务的多种方式会让用户感到困惑。如果你的app授权专用的撤销和重做按钮，使用系统提供的表中图标和把它们放到期望的地方，例如导航栏。
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.
只在当前环境执行撤销和重做操作。撤销和重做应该有一个明确和马上反应在当前环境。
For developer guidance, seeUndo Architecture.
