本文為大地瓜原創，歡迎知識共享，轉載請注明出處。
雖然你不注明出處我也沒什么精力和你計較。
作者微信號：christgreenlaw
2017-10-12日更新：
蘋果官網刪除了本文檔，已經找不到這個文檔了，好在我還有pdf版，現共享給大家。
鏈接:http://pan.baidu.com/s/1i5GKG9v 密碼:9g6z
正如文檔的名字，UIKit中的用戶界面目錄，其實簡單的來講，這篇文檔就是把常見的界面組件列了個目錄，大概介紹，而不深入。
Action Sheets
Action sheets display a set of buttons representing several alternative choices to complete a task initiated by the user. For example, when the user taps the Share button in an app’s toolbar, an action sheet appears offering a list of choices, such as Email, Print, and so on.
Action sheets展示了一組按鈕，分別表示多個選項，以完成用戶發起的任務。比如說，當用戶點擊應用中toolbar的分享按鈕時，一個action sheet就會呈現出來，提供一組選項，比如Email、Print等等。
Purpose. Action sheets allow users to://目的
- Quickly select from a list of actions//快速的從一列行為中進行選擇
- Confirm or cancel an action//確定或取消一個行為
Implementation. Action sheets are implemented in the UIActionSheet class and discussed in the UIActionSheet Class Reference.
Configuration. Action sheets are created, initialized, and configured in code, typically residing in a view controller implementation file. //通常來說，Action sheets是在一個view controller implementation file的代碼中進行創建、初始化和配置的。
Content of Action Sheets (Programmatic)
You cannot create or manipulate action sheets in Interface Builder. Rather, an action sheet floats over an existing view to interrupt its presentation, and it requires the user to dismiss it.
在IB中無法創建或操作action sheets。一個action sheet在一個已有的view上浮現以打斷其展示過程，且需要用戶來取消它。
When you create an action sheet object from the UIActionSheet class, you can initialize its most important properties with one method, initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles:. Depending on your app’s needs, that single message may be enough to configure a fully functional action sheet object, as shown in the following code. Once you have created the action sheet object, send it a show... message, such as showInView: to display the action sheet.
從
UIActionSheetClass創建以個action sheet對象時，你可以用一個方法來初始化最重要的屬性，initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles:. 根據你APP的需要，這個消息可能足夠用來完整地配置action sheet 的功能了，正如下面代碼所示。當你創建了一個action sheet對象后，向其發送一個show...消息，比如說showInView: 來展示action sheet。
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:nil
delegate:self
cancelButtonTitle:@"Cancel"
destructiveButtonTitle:@"Delete Note"
otherButtonTitles:nil];
Although the first parameter of the initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles: method enables you to provide a title for an action sheet, iOS human interface guidelines recommend that you do not use a title.
盡管initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles: 第一個參數允許你為一個action sheet提供一個title，iOS Human interface guidelines建議你不要使用title。
As described in iOS human interface guidelines, you should include a Cancel button with action sheets displayed on iPhone and with those displayed on iPad over an open popover. Otherwise on iPad, action sheets are displayed within a popover, and the user can cancel the action sheet by tapping outside the popover, in which case you do not need to include a Cancel button.
正如 iOS human interface guidelines所述，在iPhone上的action sheets應該有一個 Cancel button，iPad上open pop over出來的action sheets也應該有一個 Cancel button。否則在iPad上，action sheet是在popover中顯示的，用戶可以通過點擊popover的外部來取消action sheet，在這種情況下就不需要有 Cancel button。
To create a Cancel button, pass a non-nil value for the cancelButtonTitle: parameter of the initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles: method. A Cancel button created in this way is positioned at the bottom of the action sheet.
要創建一個 Cancel button，在 initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles:中給
cancelButtonTitle:參數傳一個非nil值。這種方式創建的Cancel button被放置在action sheet的最底部。
When your action sheet presents a potentially destructive choice, you should include a destructive button by passing a non-nil value for the destructiveButtonTitle: parameter of the initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles:
method. A destructive button created in this way is automatically colored red and positioned at the top of the action sheet.
當你的action sheet有一個潛在的destructive choice，你應該通過
initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles:
方法給destructiveButtonTitle:參數傳一個非nil值。這種方式創建的destructive button自動會變為紅色，放置在action sheet的最頂部。
Behavior of Action Sheets (Programmatic)
You can choose to present an action sheet so that it originates from a toolbar, tab bar, button bar item, from a view, or from a rectangle within a view. On iPhone, because the action sheet slides up from the bottom of a view and covers the width of the screen, most apps use showInView:. On iPad, however, action sheets appear within a popover whose arrow points to the control the user tapped to invoke the choices presented by the action sheet. So, showFromRect:inView:animated: and showFromBarButtonItem:animated: are most useful on iPad.
action sheet可以從toolbar, tab bar, button bar item, a view, a rectangle within a view等處展示出來。在iPhone上，由于action sheet從view的底部滑出，覆蓋了屏幕的寬度，大多數應用選擇使用 showInView:。然而在iPad上，action sheet在一個popover中顯示，這個popover的箭頭指向了用戶點擊以顯示action sheet的control。所以，在iPad上， 一般使用showFromRect:inView:animated: and showFromBarButtonItem:animated:。
To handle the choices presented by your action sheet, you must designate a delegate to handle the button’s action, and the delegate must conform to the UIActionSheetDelegate protocol. You designate the delegate with the delegate parameter when you initialize the action sheet object. The delegate must implement the actionSheet:clickedButtonAtIndex: message to respond when the button is tapped. For example, the following code shows an implementation that simply logs the title of the button that was tapped.
要處理action sheet所展示的選項，你需要找一個代理來處理button 的行為，這個代理必須服從
UIActionSheetDelegate協議。在初始化action sheet對象時，用delegate參數來賦值代理。代理必須實現 actionSheet:clickedButtonAtIndex: 消息來對button的點擊作出相應。比如說，下面的代碼簡單地輸出了被點擊按鈕的title。
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
NSLog(@"The %@ button was tapped.", [actionSheet buttonTitleAtIndex:buttonIndex]);
}
Using Auto Layout with Action Sheets
The layout of action sheets is handled for you. You cannot create Auto Layout constraints between an action sheet and another user interface element.
action sheet的布局不需要你處理。在action sheet和另一個用戶界面元素之間你不能創建Auto Layout約束。
For general information about using Auto Layout with iOS views, see Using Auto Layout with Views.
Making Action Sheets Accessible
Action sheets are accessible by default.
Accessibility for action sheets primarily concerns button titles. If VoiceOver is activated, it speaks the word “alert” when an action sheet is shown, then speaks its title if set (although iOS human interface guidelines recommend against titling action sheets). As the user taps a button in the action sheet, VoiceOver speaks its title and the word “button.”
action sheet默認是accessible的。action sheet的accessibility主要與button title相關。如果VoiceOver啟用，action sheet顯示的時候將會說"alert"，然后說出title（如果設置了title的話）（盡管iOS human interface guidelines不建議使用title）。用戶點擊action sheet中某個按鈕時，VoiceOver將會講出其title和“button”這個詞。
For general information about making iOS views accessible, see Making Views Accessible.
Internationalizing Action Sheets
To internationalize an action sheet, you must provide localized translations of the button titles. Button size may change depending on the language and locale.
For more information, see Internationalization and Localization Guide.
Debugging Action Sheets
When debugging issues with action sheets, watch for this common pitfall:
Not testing localizations. Be sure to test the action sheets in your app with the localizations you intend to ship. In particular, button titles can truncate if they are longer in localizations other than the one in which you designed your user interface. Following the HI guideline to give buttons short, logical titles helps to ameliorate this potential problem, but localization testing is also required.
debug action sheet時，注意這個陷阱：
Not testing localizations.
Elements Similar to an Action Sheet
與Action Sheet類似的元素
The following elements provide similar functionality to an action sheet:
Alert View. Use an alert view to convey important information about an app or the device, interrupting the user and requiring them to stop what they’re doing to choose an action or dismiss the alert. For more information, see Alert Views.
Modal View. Use a modal view (that is, the view controller uses a modal presentation style) when users initiate a self-contained subtask in the context of their workflow or another task. For more information, see UIViewController Class Reference.
以下的元素提供了與action sheet類似的功能：
Alert View。使用alert view來調查（convey）app或設備的重要信息，打斷用戶（的操作），要求用戶停止正在做的事情，選擇一個動作或者關掉alert。For more information, see Alert Views.
Modal View。當用戶初始化了一個在workflow或者另一個任務上下文中自包含的子任務時，使用modal view（也就是view controller 使用了modal展現方式）。
