UIApplication，用于应用程序级别的管理，实例是由系统自动创建的，通过类方法sharedApplication获取UIApplication实例。
typedef NS_ENUM(NSInteger, UIStatusBarStyle) { UIStatusBarStyleDefault, UIStatusBarStyleBlackTranslucent, UIStatusBarStyleBlackOpaque }; typedef NS_ENUM(NSInteger, UIStatusBarAnimation) { UIStatusBarAnimationNone, UIStatusBarAnimationFade, UIStatusBarAnimationSlide, }; // Note that UIInterfaceOrientationLandscapeLeft is equal to UIDeviceOrientationLandscapeRight (and vice versa). // This is because rotating the device to the left requires rotating the content to the right. typedef NS_ENUM(NSInteger, UIInterfaceOrientation) { UIInterfaceOrientationPortrait = UIDeviceOrientationPortrait, UIInterfaceOrientationPortraitUpsideDown = UIDeviceOrientationPortraitUpsideDown, UIInterfaceOrientationLandscapeLeft = UIDeviceOrientationLandscapeRight, UIInterfaceOrientationLandscapeRight = UIDeviceOrientationLandscapeLeft }; /* This exception is raised if supportedInterfaceOrientations returns 0, or if preferredInterfaceOrientationForPresentation returns an orientation that is not supported. */ UIKIT_EXTERN NSString *const UIApplicationInvalidInterfaceOrientationException NS_AVAILABLE_IOS(6_0); typedef NS_OPTIONS(NSUInteger, UIInterfaceOrientationMask) { UIInterfaceOrientationMaskPortrait = (1 << UIInterfaceOrientationPortrait), UIInterfaceOrientationMaskLandscapeLeft = (1 << UIInterfaceOrientationLandscapeLeft), UIInterfaceOrientationMaskLandscapeRight = (1 << UIInterfaceOrientationLandscapeRight), UIInterfaceOrientationMaskPortraitUpsideDown = (1 << UIInterfaceOrientationPortraitUpsideDown), UIInterfaceOrientationMaskLandscape = (UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight), UIInterfaceOrientationMaskAll = (UIInterfaceOrientationMaskPortrait | UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight | UIInterfaceOrientationMaskPortraitUpsideDown), UIInterfaceOrientationMaskAllButUpsideDown = (UIInterfaceOrientationMaskPortrait | UIInterfaceOrientationMaskLandscapeLeft | UIInterfaceOrientationMaskLandscapeRight), }; #define UIDeviceOrientationIsValidInterfaceOrientation(orientation) ((orientation) == UIDeviceOrientationPortrait || (orientation) == UIDeviceOrientationPortraitUpsideDown || (orientation) == UIDeviceOrientationLandscapeLeft || (orientation) == UIDeviceOrientationLandscapeRight) #define UIInterfaceOrientationIsPortrait(orientation) ((orientation) == UIInterfaceOrientationPortrait || (orientation) == UIInterfaceOrientationPortraitUpsideDown) #define UIInterfaceOrientationIsLandscape(orientation) ((orientation) == UIInterfaceOrientationLandscapeLeft || (orientation) == UIInterfaceOrientationLandscapeRight) typedef NS_OPTIONS(NSUInteger, UIRemoteNotificationType) { UIRemoteNotificationTypeNone = 0, UIRemoteNotificationTypeBadge = 1 << 0, UIRemoteNotificationTypeSound = 1 << 1, UIRemoteNotificationTypeAlert = 1 << 2, UIRemoteNotificationTypeNewsstandContentAvailability = 1 << 3, } NS_ENUM_AVAILABLE_IOS(3_0); typedef NS_ENUM(NSInteger, UIApplicationState) { UIApplicationStateActive, UIApplicationStateInactive, UIApplicationStateBackground } NS_ENUM_AVAILABLE_IOS(4_0); typedef NSUInteger UIBackgroundTaskIdentifier; UIKIT_EXTERN const UIBackgroundTaskIdentifier UIBackgroundTaskInvalid NS_AVAILABLE_IOS(4_0); UIKIT_EXTERN const NSTimeInterval UIMinimumKeepAliveTimeout NS_AVAILABLE_IOS(4_0); typedef NS_ENUM(NSInteger, UIUserInterfaceLayoutDirection) { UIUserInterfaceLayoutDirectionLeftToRight, UIUserInterfaceLayoutDirectionRightToLeft, } NS_ENUM_AVAILABLE_IOS(5_0); @class UIView, UIWindow, UIStatusBar, UIStatusBarWindow, UILocalNotification; @protocol UIApplicationDelegate; @interface UIApplication : UIResponder <UIActionSheetDelegate>+ (UIApplication *)sharedApplication; @property(nonatomic,assign) id<UIApplicationDelegate> delegate; - (void)beginIgnoringInteractionEvents; // nested. set should be set during animations & transitions to ignore touch and other events - (void)endIgnoringInteractionEvents; - (BOOL)isIgnoringInteractionEvents; // returns YES if we are at least one deep in ignoring events @property(nonatomic,getter=isIdleTimerDisabled) BOOL idleTimerDisabled; // default is NO - (BOOL)openURL:(NSURL*)url; - (BOOL)canOpenURL:(NSURL *)url NS_AVAILABLE_IOS(3_0); - (void)sendEvent:(UIEvent *)event; @property(nonatomic,readonly) UIWindow *keyWindow; @property(nonatomic,readonly) NSArray *windows; - (BOOL)sendAction:(SEL)action to:(id)target from:(id)sender forEvent:(UIEvent *)event; @property(nonatomic,getter=isNetworkActivityIndicatorVisible) BOOL networkActivityIndicatorVisible; // showing network spinning gear in status bar. default is NO @property(nonatomic) UIStatusBarStyle statusBarStyle; // default is UIStatusBarStyleDefault - (void)setStatusBarStyle:(UIStatusBarStyle)statusBarStyle animated:(BOOL)animated; @property(nonatomic,getter=isStatusBarHidden) BOOL statusBarHidden; - (void)setStatusBarHidden:(BOOL)hidden withAnimation:(UIStatusBarAnimation)animation NS_AVAILABLE_IOS(3_2); // Rotate to a specific orientation. This only rotates the status bar and updates the statusBarOrientation property. // This does not change automatically if the device changes orientation. // Explicit setting of the status bar orientation is more limited in iOS 6.0 and later. @property(nonatomic) UIInterfaceOrientation statusBarOrientation; - (void)setStatusBarOrientation:(UIInterfaceOrientation)interfaceOrientation animated:(BOOL)animated; // The system only calls this method if the application delegate has not // implemented the delegate equivalent. It returns the orientations specified by // the application's info.plist. If no supported interface orientations were // specified it will return UIInterfaceOrientationMaskAll on an iPad and // UIInterfaceOrientationMaskAllButUpsideDown on a phone. The return value // should be one of the UIInterfaceOrientationMask values which indicates the // orientations supported by this application. - (NSUInteger)supportedInterfaceOrientationsForWindow:(UIWindow *)window NS_AVAILABLE_IOS(6_0); @property(nonatomic,readonly) NSTimeInterval statusBarOrientationAnimationDuration; // Returns the animation duration for the status bar during a 90 degree orientation change. It should be doubled for a 180 degree orientation change. @property(nonatomic,readonly) CGRect statusBarFrame; // returns CGRectZero if the status bar is hidden @property(nonatomic) NSInteger applicationIconBadgeNumber; // set to 0 to hide. default is 0 @property(nonatomic) BOOL applicationSupportsShakeToEdit NS_AVAILABLE_IOS(3_0); @property(nonatomic,readonly) UIApplicationState applicationState NS_AVAILABLE_IOS(4_0); @property(nonatomic,readonly) NSTimeInterval backgroundTimeRemaining NS_AVAILABLE_IOS(4_0); - (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:(void(^)(void))handler NS_AVAILABLE_IOS(4_0); - (void)endBackgroundTask:(UIBackgroundTaskIdentifier)identifier NS_AVAILABLE_IOS(4_0); - (BOOL)setKeepAliveTimeout:(NSTimeInterval)timeout handler:(void(^)(void))keepAliveHandler NS_AVAILABLE_IOS(4_0); - (void)clearKeepAliveTimeout NS_AVAILABLE_IOS(4_0); @property(nonatomic,readonly,getter=isProtectedDataAvailable) BOOL protectedDataAvailable NS_AVAILABLE_IOS(4_0); @property(nonatomic,readonly) UIUserInterfaceLayoutDirection userInterfaceLayoutDirection NS_AVAILABLE_IOS(5_0); @end @interface UIApplication (UIRemoteNotifications) - (void)registerForRemoteNotificationTypes:(UIRemoteNotificationType)types NS_AVAILABLE_IOS(3_0); - (void)unregisterForRemoteNotifications NS_AVAILABLE_IOS(3_0); // calls -registerForRemoteNotificationTypes with UIRemoteNotificationTypeNone // returns the enabled types, also taking into account any systemwide settings; doesn't relate to connectivity - (UIRemoteNotificationType)enabledRemoteNotificationTypes NS_AVAILABLE_IOS(3_0); @end @interface UIApplication (UILocalNotifications) - (void)presentLocalNotificationNow:(UILocalNotification *)notification NS_AVAILABLE_IOS(4_0); - (void)scheduleLocalNotification:(UILocalNotification *)notification NS_AVAILABLE_IOS(4_0); // copies notification - (void)cancelLocalNotification:(UILocalNotification *)notification NS_AVAILABLE_IOS(4_0); - (void)cancelAllLocalNotifications NS_AVAILABLE_IOS(4_0); @property(nonatomic,copy) NSArray *scheduledLocalNotifications NS_AVAILABLE_IOS(4_0); // setter added in iOS 4.2 @end @interface UIApplication (UIRemoteControlEvents) - (void)beginReceivingRemoteControlEvents NS_AVAILABLE_IOS(4_0); - (void)endReceivingRemoteControlEvents NS_AVAILABLE_IOS(4_0); @end @interface UIApplication (UINewsstand) - (void)setNewsstandIconImage:(UIImage *)image; @end @interface UIApplication (UIStateRestoration) // These methods are used to inform the system that state restoration is occuring asynchronously after the application // has processed its restoration archive on launch. In the even of a crash, the system will be able to detect that it may // have been caused by a bad restoration archive and arrange to ignore it on a subsequent application launch. - (void)extendStateRestoration NS_AVAILABLE_IOS(6_0); - (void)completeStateRestoration NS_AVAILABLE_IOS(6_0); @end
UIApplicationDelegate，用于处理应用程序生命周期中各事件的。我们的应用程序中都会实现这个协议
@protocol UIApplicationDelegate<NSObject> @optional // 看事件处理委托的名字，基本可以理解其意义 - (void)applicationDidFinishLaunching:(UIApplication *)application; - (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions NS_AVAILABLE_IOS(6_0); - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions NS_AVAILABLE_IOS(3_0); - (void)applicationDidBecomeActive:(UIApplication *)application; - (void)applicationWillResignActive:(UIApplication *)application; - (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url; // Will be deprecated at some point, please replace with application:openURL:sourceApplication:annotation: - (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation NS_AVAILABLE_IOS(4_2); // no equiv. notification. return NO if the application can't open for some reason - (void)applicationDidReceiveMemoryWarning:(UIApplication *)application; // try to clean up as much memory as possible. next step is to terminate app - (void)applicationWillTerminate:(UIApplication *)application; - (void)applicationSignificantTimeChange:(UIApplication *)application; // midnight, carrier time update, daylight savings time change - (void)application:(UIApplication *)application willChangeStatusBarOrientation:(UIInterfaceOrientation)newStatusBarOrientation duration:(NSTimeInterval)duration; - (void)application:(UIApplication *)application didChangeStatusBarOrientation:(UIInterfaceOrientation)oldStatusBarOrientation; - (void)application:(UIApplication *)application willChangeStatusBarFrame:(CGRect)newStatusBarFrame; // in screen coordinates - (void)application:(UIApplication *)application didChangeStatusBarFrame:(CGRect)oldStatusBarFrame; // one of these will be called after calling -registerForRemoteNotifications - (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken NS_AVAILABLE_IOS(3_0); - (void)application:(UIApplication *)application didFailToRegisterForRemoteNotificationsWithError:(NSError *)error NS_AVAILABLE_IOS(3_0); - (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo NS_AVAILABLE_IOS(3_0); - (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification NS_AVAILABLE_IOS(4_0); - (void)applicationDidEnterBackground:(UIApplication *)application NS_AVAILABLE_IOS(4_0); - (void)applicationWillEnterForeground:(UIApplication *)application NS_AVAILABLE_IOS(4_0); - (void)applicationProtectedDataWillBecomeUnavailable:(UIApplication *)application NS_AVAILABLE_IOS(4_0); - (void)applicationProtectedDataDidBecomeAvailable:(UIApplication *)application NS_AVAILABLE_IOS(4_0); @property (nonatomic, retain) UIWindow *window NS_AVAILABLE_IOS(5_0); - (NSUInteger)application:(UIApplication *)application supportedInterfaceOrientationsForWindow:(UIWindow *)window NS_AVAILABLE_IOS(6_0); #pragma mark -- State Restoration protocol adopted by UIApplication delegate -- - (UIViewController *) application:(UIApplication *)application viewControllerWithRestorationIdentifierPath:(NSArray *)identifierComponents coder:(NSCoder *)coder NS_AVAILABLE_IOS(6_0); - (BOOL) application:(UIApplication *)application shouldSaveApplicationState:(NSCoder *)coder NS_AVAILABLE_IOS(6_0); - (BOOL) application:(UIApplication *)application shouldRestoreApplicationState:(NSCoder *)coder NS_AVAILABLE_IOS(6_0); - (void) application:(UIApplication *)application willEncodeRestorableStateWithCoder:(NSCoder *)coder NS_AVAILABLE_IOS(6_0); - (void) application:(UIApplication *)application didDecodeRestorableStateWithCoder:(NSCoder *)coder NS_AVAILABLE_IOS(6_0); @end @interface UIApplication(UIApplicationDeprecated) @property(nonatomic,getter=isProximitySensingEnabled) BOOL proximitySensingEnabled NS_DEPRECATED_IOS(2_0, 3_0); // default is NO. see UIDevice for replacement - (void)setStatusBarHidden:(BOOL)hidden animated:(BOOL)animated NS_DEPRECATED_IOS(2_0, 3_2); // use -setStatusBarHidden:withAnimation: @end // If nil is specified for principalClassName, the value for NSPrincipalClass from the Info.plist is used. If there is no // NSPrincipalClass key specified, the UIApplication class is used. The delegate class will be instantiated using init. UIKIT_EXTERN int UIApplicationMain(int argc, char *argv[], NSString *principalClassName, NSString *delegateClassName); UIKIT_EXTERN NSString *const UITrackingRunLoopMode; // These notifications are sent out after the equivalent delegate message is called UIKIT_EXTERN NSString *const UIApplicationDidEnterBackgroundNotification NS_AVAILABLE_IOS(4_0); UIKIT_EXTERN NSString *const UIApplicationWillEnterForegroundNotification NS_AVAILABLE_IOS(4_0); UIKIT_EXTERN NSString *const UIApplicationDidFinishLaunchingNotification; UIKIT_EXTERN NSString *const UIApplicationDidBecomeActiveNotification; UIKIT_EXTERN NSString *const UIApplicationWillResignActiveNotification; UIKIT_EXTERN NSString *const UIApplicationDidReceiveMemoryWarningNotification; UIKIT_EXTERN NSString *const UIApplicationWillTerminateNotification; UIKIT_EXTERN NSString *const UIApplicationSignificantTimeChangeNotification; UIKIT_EXTERN NSString *const UIApplicationWillChangeStatusBarOrientationNotification; // userInfo contains NSNumber with new orientation UIKIT_EXTERN NSString *const UIApplicationDidChangeStatusBarOrientationNotification; // userInfo contains NSNumber with old orientation UIKIT_EXTERN NSString *const UIApplicationStatusBarOrientationUserInfoKey; // userInfo dictionary key for status bar orientation UIKIT_EXTERN NSString *const UIApplicationWillChangeStatusBarFrameNotification; // userInfo contains NSValue with new frame UIKIT_EXTERN NSString *const UIApplicationDidChangeStatusBarFrameNotification; // userInfo contains NSValue with old frame UIKIT_EXTERN NSString *const UIApplicationStatusBarFrameUserInfoKey; // userInfo dictionary key for status bar frame UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsURLKey NS_AVAILABLE_IOS(3_0); // userInfo contains NSURL with launch URL UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsSourceApplicationKey NS_AVAILABLE_IOS(3_0); // userInfo contains NSString with launch app bundle ID UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsRemoteNotificationKey NS_AVAILABLE_IOS(3_0); // userInfo contains NSDictionary with payload UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsLocalNotificationKey NS_AVAILABLE_IOS(4_0); // userInfo contains a UILocalNotification UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsAnnotationKey NS_AVAILABLE_IOS(3_2); // userInfo contains object with annotation property list UIKIT_EXTERN NSString *const UIApplicationProtectedDataWillBecomeUnavailable NS_AVAILABLE_IOS(4_0); UIKIT_EXTERN NSString *const UIApplicationProtectedDataDidBecomeAvailable NS_AVAILABLE_IOS(4_0); UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsLocationKey NS_AVAILABLE_IOS(4_0); // app was launched in response to a CoreLocation event. UIKIT_EXTERN NSString *const UIApplicationLaunchOptionsNewsstandDownloadsKey NS_AVAILABLE_IOS(5_0); // userInfo contains an NSArray of NKAssetDownload identifiers
UIWindows，每个应用程序只有一个窗口，需要我们在程序启动时创建。
@interface UIWindow : UIView @property(nonatomic,retain) UIScreen *screen NS_AVAILABLE_IOS(3_2); // default is [UIScreen mainScreen]. changing the screen may be an expensive operation and should not be done in performance-sensitive code @property(nonatomic) UIWindowLevel windowLevel; // default = 0.0 @property(nonatomic,readonly,getter=isKeyWindow) BOOL keyWindow; - (void)becomeKeyWindow; // override point for subclass. Do not call directly - (void)resignKeyWindow; // override point for subclass. Do not call directly - (void)makeKeyWindow; - (void)makeKeyAndVisible; // convenience. most apps call this to show the main window and also make it key. otherwise use view hidden property @property(nonatomic,retain) UIViewController *rootViewController NS_AVAILABLE_IOS(4_0); // default is nil - (void)sendEvent:(UIEvent *)event; // called by UIApplication to dispatch events to views inside the window - (CGPoint)convertPoint:(CGPoint)point toWindow:(UIWindow *)window; // can be used to convert to another window - (CGPoint)convertPoint:(CGPoint)point fromWindow:(UIWindow *)window; // pass in nil to mean screen - (CGRect)convertRect:(CGRect)rect toWindow:(UIWindow *)window; - (CGRect)convertRect:(CGRect)rect fromWindow:(UIWindow *)window; @end UIKIT_EXTERN const UIWindowLevel UIWindowLevelNormal; UIKIT_EXTERN const UIWindowLevel UIWindowLevelAlert; UIKIT_EXTERN const UIWindowLevel UIWindowLevelStatusBar; UIKIT_EXTERN NSString *const UIWindowDidBecomeVisibleNotification; // nil UIKIT_EXTERN NSString *const UIWindowDidBecomeHiddenNotification; // nil UIKIT_EXTERN NSString *const UIWindowDidBecomeKeyNotification; // nil UIKIT_EXTERN NSString *const UIWindowDidResignKeyNotification; // nil // Each notification includes a nil object and a userInfo dictionary containing the // begining and ending keyboard frame in screen coordinates. Use the various UIView and // UIWindow convertRect facilities to get the frame in the desired coordinate system. // Animation key/value pairs are only available for the "will" family of notification. UIKIT_EXTERN NSString *const UIKeyboardWillShowNotification; UIKIT_EXTERN NSString *const UIKeyboardDidShowNotification; UIKIT_EXTERN NSString *const UIKeyboardWillHideNotification; UIKIT_EXTERN NSString *const UIKeyboardDidHideNotification; UIKIT_EXTERN NSString *const UIKeyboardFrameBeginUserInfoKey NS_AVAILABLE_IOS(3_2); // NSValue of CGRect UIKIT_EXTERN NSString *const UIKeyboardFrameEndUserInfoKey NS_AVAILABLE_IOS(3_2); // NSValue of CGRect UIKIT_EXTERN NSString *const UIKeyboardAnimationDurationUserInfoKey NS_AVAILABLE_IOS(3_0); // NSNumber of double UIKIT_EXTERN NSString *const UIKeyboardAnimationCurveUserInfoKey NS_AVAILABLE_IOS(3_0); // NSNumber of NSUInteger (UIViewAnimationCurve) // Like the standard keyboard notifications above, these additional notifications include // a nil object and begin/end frames of the keyboard in screen coordinates in the userInfo dictionary. UIKIT_EXTERN NSString *const UIKeyboardWillChangeFrameNotification NS_AVAILABLE_IOS(5_0); UIKIT_EXTERN NSString *const UIKeyboardDidChangeFrameNotification NS_AVAILABLE_IOS(5_0); // These keys are superseded by UIKeyboardFrameBeginUserInfoKey and UIKeyboardFrameEndUserInfoKey. UIKIT_EXTERN NSString *const UIKeyboardCenterBeginUserInfoKey NS_DEPRECATED_IOS(2_0, 3_2); UIKIT_EXTERN NSString *const UIKeyboardCenterEndUserInfoKey NS_DEPRECATED_IOS(2_0, 3_2); UIKIT_EXTERN NSString *const UIKeyboardBoundsUserInfoKey NS_DEPRECATED_IOS(2_0, 3_2);
UIScreen 常用的方法
// 取得屏幕大小 CGRect *rect = [[UIScreen mainScreen] bounds];
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIScreen : NSObject { + (NSArray *)screens NS_AVAILABLE_IOS(3_2); // all screens currently attached to the device + (UIScreen *)mainScreen; // the device's internal screen @property(nonatomic,readonly) CGRect bounds; // Bounds of entire screen in points @property(nonatomic,readonly) CGRect applicationFrame; // Frame of application screen area in points (i.e. entire screen minus status bar if visible) @property(nonatomic,readonly) CGFloat scale NS_AVAILABLE_IOS(4_0); @property(nonatomic,readonly,copy) NSArray *availableModes NS_AVAILABLE_IOS(3_2); // The list of modes that this screen supports @property(nonatomic,readonly,retain) UIScreenMode *preferredMode NS_AVAILABLE_IOS(4_3); // Preferred mode of this screen. Choosing this mode will likely produce the best results @property(nonatomic,retain) UIScreenMode *currentMode NS_AVAILABLE_IOS(3_2); // Current mode of this screen @property(nonatomic) UIScreenOverscanCompensation overscanCompensation NS_AVAILABLE_IOS(5_0); // Default is UIScreenOverscanCompensationScale. Determines how the screen behaves if the connected display is overscanning @property(nonatomic,readonly,retain) UIScreen *mirroredScreen NS_AVAILABLE_IOS(4_3); // The screen being mirrored by the receiver. nil if mirroring is disabled or unsupported. Moving a UIWindow to this screen will disable mirroring @property(nonatomic) CGFloat brightness NS_AVAILABLE_IOS(5_0); // 0 .. 1.0, where 1.0 is maximum brightness. Only supported by main screen. @property(nonatomic) BOOL wantsSoftwareDimming NS_AVAILABLE_IOS(5_0); // Default is NO. If YES, brightness levels lower than that of which the hardware is capable are emulated in software, if neccessary. Having enabled may entail performance cost. - (CADisplayLink *)displayLinkWithTarget:(id)target selector:(SEL)sel NS_AVAILABLE_IOS(4_0); @end