使用通知监听屏幕的旋转可以有效的避免viewcontrollor判断转向错误的问题

本文链接：https://blog.youkuaiyun.com/TPphy/article/details/39047151

本文介绍了一个iOS应用如何监听设备的方向变化，并根据不同方向执行相应的操作。通过注册设备方向通知，使用NSNotification来实现对设备方向的监听。

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-(void)viewWillAppear:(BOOL)animated{

    UIDevice *device = [UIDevice currentDevice]; //Get the device object
    [device beginGeneratingDeviceOrientationNotifications]; //Tell it to start monitoring the accelerometer for orientation
    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter]; //Get the notification centre for the app
    [nc addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification  object:device];
}
-(void)viewWillDisappear:(BOOL)animated {
    
    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
    UIDevice *device = [UIDevice currentDevice]; //Get the device object
    [nc removeObserver:self name:UIDeviceOrientationDidChangeNotification object:device];
}

- (void)orientationChanged:(NSNotification *)note  {
    UIDeviceOrientation  status= [[UIDevice currentDevice] orientation];
    switch (status) {
        case UIDeviceOrientationPortrait:            // Device oriented vertically, home button on the bottom
            [self dismissViewControllerAnimated:YES completion:nil];
            break;
        case UIDeviceOrientationPortraitUpsideDown:  // Device oriented vertically, home button on the top
            break;
        case UIDeviceOrientationLandscapeLeft:      // Device oriented horizontally, home button on the right
            ;
            break;
        case UIDeviceOrientationLandscapeRight:      // Device oriented horizontally, home button on the left
            
            ;
            break;
        default:
            break;
    }
}