手机朝向监测

//添加监测

- (void)addNotification {
    [//返回一个UIDevice实例；
     [UIDevice currentDevice]beginGeneratingDeviceOrientationNotifications];//改变朝向则获悉这一点；
    
    [[NSNotificationCenter defaultCenter] addObserver:self  selector:@selector(orientationChanged:)   name:@"UIDeviceOrientationDidChangeNotification"
     object:nil];
}

//实现方法orientationChanged；
-(void)orientationChanged:(NSNotification*)notification
{UIDeviceOrientation orientation=[[UIDevice currentDevice]orientation];

    switch (orientation) {

        case UIDeviceOrientationFaceUp:
            self.orientationLabel.text=@"Face Up!";
            break;

        case UIDeviceOrientationFaceDown:
            self.orientationLabel.text=@"Face Down!";
            break;

        case UIDeviceOrientationPortrait:
            self.orientationLabel.text=@"Standing Up!";
            break;

        case UIDeviceOrientationLandscapeLeft:
            self.orientationLabel.text=@"Left Side!";
            break;

       case UIDeviceOrientationLandscapeRight:
            self.orientationLabel.text=@"Right Side!";
            break;
      
        default:
            self.orientationLabel.text=@"Unknown!";
            break;
    }

}