运用UIDevice类获取屏幕方向

UIDevice类中，通过orientation属性可以获知6个方向的信息，除了横竖屏4个方向之外，还可以获取到正面朝上，还是正面朝下。
/UIDeviceOrientation枚举类型/

typedef NS_ENUM(NSInteger, UIDeviceOrientation) { 
    UIDeviceOrientationUnknown, 
    UIDeviceOrientationPortrait,   // 竖屏，正常状态 
    UIDeviceOrientationPortraitUpsideDown,  // 竖屏，倒置 
    UIDeviceOrientationLandscapeLeft,       // 向左横屏  
    UIDeviceOrientationLandscapeRight,      // 向右横屏
    UIDeviceOrientationFaceUp,              //正面朝上 
    UIDeviceOrientationFaceDown             // 正面朝下
 } 

示例代码

下方的示例代码，当用户改变手机朝向时，可以在当前屏幕的Label显示当前的朝向。
(1) 在viewDidLoad方法中，启动方向通知，并在通知中心注册观察者。

- (void)viewDidLoad {
    [super viewDidLoad];
    UIDevice *device = [UIDevice currentDevice];
    //开启方向改变通知
    [device beginGeneratingDeviceOrientationNotifications];
    //注册方向改变通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChange) name:UIDeviceOrientationDidChangeNotification object:nil];   
}

(2) 当收到方向改变通知时，调用orientationChange方法，更新Label的文字显示。

-(void) orientationChange{
     UIDevice *device = [UIDevice currentDevice];
        switch (device.orientation) {
         case UIDeviceOrientationPortrait: 
            self.orientationLabel.text = [NSString stringWithFormat:@"竖屏/正常"]; 
            break;
         case UIDeviceOrientationPortraitUpsideDown: 
            self.orientationLabel.text = [NSString stringWithFormat:@"竖屏/倒置"]; 
            break; 
        case UIDeviceOrientationLandscapeLeft: 
            self.orientationLabel.text = [NSString stringWithFormat:@"横屏/左侧"]; 
            break; 
        case UIDeviceOrientationLandscapeRight:
             self.orientationLabel.text = [NSString stringWithFormat:@"横屏/右侧"];
             break; 
        case UIDeviceOrientationFaceUp: 
            self.orientationLabel.text = [NSString stringWithFormat:@"正面朝上"]; 
            break; 
        case UIDeviceOrientationFaceDown: 
            self.orientationLabel.text = [NSString stringWithFormat:@"正面朝下"]; 
            break;
                   default:
             self.orientationLabel.text = [NSString stringWithFormat:@"未知朝向"]; 
            break;
     }
 }

(3) 在dealloc方法中注销通知。

-(void)dealloc {
     //移除观察者
     [[NSNotificationCenter defaultCenter] removeObserver:self];
 }