概述
如果要和UIActionSheet对象交互，那么UIViewController类的h文件需要遵循UIActionSheetDelegate协议。示例代码：
@interface BIDViewController : UIViewController
并且，需要在UIViewController类的m文件中构造一个UIActionSheet对象，同时实现协议的方法。示例代码：
- (IBAction)buttonPressed:(id)sender { UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Are you sure?" delegate:self cancelButtonTitle:@"No Way!" destructiveButtonTitle:@"Yes, I’m Sure!" otherButtonTitles:nil]; [actionSheet showInView:self.view]; }
delegate参数就是UIActionSheet的委托对象，在这个例子中，传入的selt就是BIDViewController对象本身，因为它实现了UIActionSheetDelegate协议。
调用showInView:方法，此处传入BIDViewController对象的view实例，从而可以在BIDViewController的页面上显示出UIActionSheet。
- (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex { if (buttonIndex != [actionSheet cancelButtonIndex]) { NSString *msg = nil; if (self.nameField.text.length > 0) msg = [NSString stringWithFormat: @"You can breathe easy, %@, everything went OK.", self.nameField.text]; else msg = @"You can breathe easy, everything went OK."; UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Something was done" message:msg delegate:self cancelButtonTitle:@"Phew!" otherButtonTitles:nil]; [alert show]; } }
通过buttonIndex参数判断点击的是哪个按钮。
附
该协议的描述。
The UIActionSheetDelegate protocol defines the methods a delegate of a UIActionSheet object should implement. The delegate implements the button actions and any other custom behavior. Some of the methods defined in this protocol are optional.
声明了一些UIActionSheet的委托对象需要实现的一些方法。
该协议的源码。
// // UIActionSheet.h // UIKit // // Copyright 2010-2012, Apple Inc. All rights reserved. // #import #import #import #import @protocol UIActionSheetDelegate; @class UILabel, UIToolbar, UITabBar, UIWindow, UIBarButtonItem, UIPopoverController; typedef NS_ENUM(NSInteger, UIActionSheetStyle) { UIActionSheetStyleAutomatic = -1, // take appearance from toolbar style otherwise uses 'default' UIActionSheetStyleDefault = UIBarStyleDefault, UIActionSheetStyleBlackTranslucent = UIBarStyleBlackTranslucent, UIActionSheetStyleBlackOpaque = UIBarStyleBlackOpaque, }; NS_CLASS_AVAILABLE_IOS(2_0) @interface UIActionSheet : UIView { @private id _delegate; UILabel *_titleLabel; NSAttributedString *_attributedTitleString; UILabel *_subtitleLabel; UILabel *_bodyTextLabel; UILabel *_taglineTextLabel; CGFloat _startY; id _context; NSInteger _cancelButton; NSInteger _defaultButton; NSInteger _firstOtherButton; UIToolbar *_toolbar; UIWindow *_originalWindow; UIWindow *_dimWindow; NSInteger _suspendTag; NSInteger _dismissButtonIndex; CGFloat _bodyTextHeight; NSMutableArray *_buttons; NSMutableArray *_buttonsInTable; NSMutableArray *_textFields; UIView *_keyboard; UIView *_table; UIView *_buttonTableView; UIView *_dimView; UIPopoverController * _popoverController; CGFloat _fontSizeInTableView; // font size for 'complex' buttons (phone numbers || doc interaction controller) CGFloat _iconOffset; // doc interaction controller app icon CGFloat _labelOffset; // phone numbers layout CGFloat _labelWidth; CGFloat _titleWidth; BOOL _oldIgnoreTapsValue; struct { unsigned int numberOfRows:7; unsigned int delegateAlertSheetButtonClicked:1; unsigned int delegateDidPresentAlertSheet:1; unsigned int delegateDidDismissAlertSheet:1; unsigned int hideButtonBar:1; unsigned int alertStyle:3; unsigned int dontDimBackground:1; unsigned int dismissSuspended:1; unsigned int dontBlockInteraction:1; unsigned int sheetWasPoppedUp:1; unsigned int sheetWasShown:1; unsigned int animating:1; unsigned int hideWhenDoneAnimating:1; unsigned int layoutWhenDoneAnimating:1; unsigned int titleMaxLineCount:2; unsigned int bodyTextMaxLineCount:3; unsigned int runsModal:1; unsigned int runningModal:1; unsigned int addedTextView:1; unsigned int addedTableShadows:1; unsigned int showOverSBAlerts:1; unsigned int showMinTableContent:1; unsigned int bodyTextTruncated:1; unsigned int orientation:3; unsigned int popupFromPoint:1; unsigned int inPopover:1; unsigned int delegateBodyTextAlignment:1; unsigned int delegateClickedButtonAtIndex:1; unsigned int delegateClickedButtonAtIndex2:1; unsigned int delegateCancel:1; unsigned int delegateCancel2:1; unsigned int delegateWillPresent:1; unsigned int delegateWillPresent2:1; unsigned int delegateDidPresent:1; unsigned int delegateDidPresent2:1; unsigned int delegateWillDismiss:1; unsigned int delegateWillDismiss2:1; unsigned int delegateDidDismiss:1; unsigned int delegateDidDismiss2:1; unsigned int dontCallDismissDelegate:1; unsigned int useAutomaticKB:1; unsigned int twoColumnsLayoutMode:7; // one column || even width (leaves empty space) || first button wider || last button wider unsigned int threeColumnsLayoutMode:7; // one column || even width (leaves empty space) || first button wider || last button wider unsigned int shouldHandleFirstKeyUpEvent:1; // when presenting with hardware KB we have to handle the first key up event we get so we don't end up repeating the last key unsigned int cancelWhenDoneAnimating:1; unsigned int useThreePartButtons:1; // phone numbers layout unsigned int useTwoPartButtons:1; // doc interaction layout unsigned int displaySelectedButtonGlyph:1; int indexOfSelectedButton:7; // default -1 (no checkmark) otherwise will display a checkbox (this for the airtunes action sheet) unsigned int useCustomSelectedButtonGlyph:1; } _modalViewFlags; UIActionSheetStyle _actionSheetStyle; UIImage *_selectedButtonGlyphImage; UIImage *_selectedButtonGlyphHighlightedImage; UIImageView *_shadowImageView; } - (id)initWithTitle:(NSString *)title delegate:(id)delegate cancelButtonTitle:(NSString *)cancelButtonTitle destructiveButtonTitle:(NSString *)destructiveButtonTitle otherButtonTitles:(NSString *)otherButtonTitles, ... NS_REQUIRES_NIL_TERMINATION; @property(nonatomic,assign) id delegate; // weak reference @property(nonatomic,copy) NSString *title; @property(nonatomic) UIActionSheetStyle actionSheetStyle; // default is UIActionSheetStyleAutomatic. ignored if alert is visible // adds a button with the title. returns the index (0 based) of where it was added. buttons are displayed in the order added except for the // destructive and cancel button which will be positioned based on HI requirements. buttons cannot be customized. - (NSInteger)addButtonWithTitle:(NSString *)title; // returns index of button. 0 based. - (NSString *)buttonTitleAtIndex:(NSInteger)buttonIndex; @property(nonatomic,readonly) NSInteger numberOfButtons; @property(nonatomic) NSInteger cancelButtonIndex; // if the delegate does not implement -actionSheetCancel:, we pretend this button was clicked on. default is -1 @property(nonatomic) NSInteger destructiveButtonIndex; // sets destructive (red) button. -1 means none set. default is -1. ignored if only one button @property(nonatomic,readonly) NSInteger firstOtherButtonIndex; // -1 if no otherButtonTitles or initWithTitle:... not used @property(nonatomic,readonly,getter=isVisible) BOOL visible; // show a sheet animated. you can specify either a toolbar, a tab bar, a bar butto item or a plain view. We do a special animation if the sheet rises from // a toolbar, tab bar or bar button item and we will automatically select the correct style based on the bar style. if not from a bar, we use // UIActionSheetStyleDefault if automatic style set - (void)showFromToolbar:(UIToolbar *)view; - (void)showFromTabBar:(UITabBar *)view; - (void)showFromBarButtonItem:(UIBarButtonItem *)item animated:(BOOL)animated NS_AVAILABLE_IOS(3_2); - (void)showFromRect:(CGRect)rect inView:(UIView *)view animated:(BOOL)animated NS_AVAILABLE_IOS(3_2); - (void)showInView:(UIView *)view; // hides alert sheet or popup. use this method when you need to explicitly dismiss the alert. // it does not need to be called if the user presses on a button - (void)dismissWithClickedButtonIndex:(NSInteger)buttonIndex animated:(BOOL)animated; @end @protocol UIActionSheetDelegate @optional // Called when a button is clicked. The view will be automatically dismissed after this call returns - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex; // Called when we cancel a view (eg. the user clicks the Home button). This is not called when the user clicks the cancel button. // If not defined in the delegate, we simulate a click in the cancel button - (void)actionSheetCancel:(UIActionSheet *)actionSheet; - (void)willPresentActionSheet:(UIActionSheet *)actionSheet; // before animation and showing view - (void)didPresentActionSheet:(UIActionSheet *)actionSheet; // after animation - (void)actionSheet:(UIActionSheet *)actionSheet willDismissWithButtonIndex:(NSInteger)buttonIndex; // before animation and hiding view - (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex; // after animation @end
参考资料
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIActionSheet_Class/
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIModalViewDelegate_Protocol/
https://developer.apple.com/library/IOS/documentation/UserExperience/Conceptual/UIKitUICatalog/UIActionSheet.html