使用Orientation Changed Notification遇到的問題及解決辦法

有些情況下uiviewcontroller內建的rotate方法會不起作用，所以需要使用uidevice的Orientation Changed Notification方法

Orientation Changed Notification使用方法：

Orientation Changed NotificationAdd to #AppDelegate.m didFinishLaunchingWithOptions

//----- SETUP DEVICE ORIENTATION CHANGE NOTIFICATION -----UIDevice *device = [UIDevice currentDevice];//Get the device object[device beginGeneratingDeviceOrientationNotifications];//Tell it to start monitoring the accelerometer for orientationNSNotificationCenter *nc = [NSNotificationCenter defaultCenter];//Get the notification centre for the app[nc addObserver:self//Add yourself as an observer   selector:@selector(orientationChanged:)   name:UIDeviceOrientationDidChangeNotification object:device];

Function To Receive Notification Message

//********** ORIENTATION CHANGED **********- (void)orientationChanged:(NSNotification *)note{NSLog(@"Orientation  has changed: %d", [[note object] orientation]);}

不過這樣會有個問題，那就是UIDeviceOrientation是有6種，而UIInterfaceOrientation是4種，這樣在使用UIDeviceOrientationIsPortrait的時候如果取反就會包含unknown或者faceup等情況

typedef enum {   UIDeviceOrientationUnknown,   UIDeviceOrientationPortrait,   UIDeviceOrientationPortraitUpsideDown,   UIDeviceOrientationLandscapeLeft,   UIDeviceOrientationLandscapeRight,   UIDeviceOrientationFaceUp,   UIDeviceOrientationFaceDown} UIDeviceOrientation;

解決方案：在orientationChanged:(NSNotification *)note中加入如下代碼：

if ([[note
object] orientation] ==
UIDeviceOrientationUnknown ||

        [[note
object] orientation] ==
UIDeviceOrientationFaceUp  ||

        [[note
object] orientation] ==
UIDeviceOrientationFaceDown) return;

這樣就可以放心使用UIDeviceOrientationIsPortrait了