1、UIDeviceOrientation
UIDeviceOrientation的定义在UIDevice.h中，它的定义如下：
// UIDevice.h
...
typedef NS_ENUM(NSInteger, UIDeviceOrientation) {
UIDeviceOrientationUnknown,
UIDeviceOrientationPortrait, // Device oriented vertically, home button on the bottom
UIDeviceOrientationPortraitUpsideDown, // Device oriented vertically, home button on the top
UIDeviceOrientationLandscapeLeft, // Device oriented horizontally, home button on the right
UIDeviceOrientationLandscapeRight, // Device oriented horizontally, home button on the left
UIDeviceOrientationFaceUp, // Device oriented flat, face up
UIDeviceOrientationFaceDown // Device oriented flat, face down
};
由此可见，设备方向有7种，这是一个三维的方向体系，每个方向一种，再加上一种不可判断的。
人为判断设备方向的方法：通过home按钮定位。注意：设备方向左时home按钮在右边，设备方向右时home按钮在左边。
程序获取设备方向的方法是：[[UIDevicecurrentDevice] orientation]
2、UIInterfaceOrientation
UIInterfaceOrientation的定义在UIApplication.h中，它的定义如下：
//
// UIApplication.h
...
// 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
};
由此可见，界面方向是二维的，界面方向的左和右跟home按钮的左右相同。
人工判断界面方向的方法是：木有方法判断界面方向，界面方向取决于程序实现。
程序获取界面方向的方法是：[[UIApplicationsharedApplication] statusBarOrientation]
3.UIInterfaceOrientationMask
UIInterfaceOrientation的定义在UIApplication.h中，它的定义如下：
//
// UIApplication.h
...
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),
};
由UIInterfaceOrientationMask的名称可以知道，它只是为了支持多种UIInterfaceOrientation而定义的类型。
它跟UIViewController相关，在UIViewController中可以通过[self supportedInterfaceOrientations]获取支持的UIInterfaceOrientation。