在 iOS 8 中不推荐使用 didRotateFromInterfaceOrientation

Question

自 iOS 8.0 起，didRotateFromInterfaceOrientation 功能已被弃用，我现在不知道如何正确更改 AVCaptureVideoPreviewLayer 的方向。

根据"interfaceOrientation" is deprecated in iOS 8, How to change this method Objective C，我有以下工作代码来获取基于statusBarOrientation 的AVCaptureVideoOrientation：

- (AVCaptureVideoOrientation)getOrientation {
    // Translate the orientation
    switch ([[UIApplication sharedApplication] statusBarOrientation]) {
        case UIInterfaceOrientationPortrait:
            return AVCaptureVideoOrientationPortrait;
        case UIInterfaceOrientationPortraitUpsideDown:
            return AVCaptureVideoOrientationPortraitUpsideDown;
        case UIInterfaceOrientationLandscapeLeft:
            return AVCaptureVideoOrientationLandscapeLeft;
        case UIInterfaceOrientationLandscapeRight:
            return AVCaptureVideoOrientationLandscapeRight;
        default:
            return AVCaptureVideoOrientationPortrait;
    }
}

当方向改变时我需要调用以下函数：

[self.videoPreviewLayer.connection setVideoOrientation:[self getOrientation]];

但我不知道把它放在哪里合适。

尝试 1

由于 didRotateFromInterfaceOrientation 已弃用且 Apple 建议使用 viewWillTransitionToSize:withTransitionCoordinator:，因此尝试一下似乎很自然：

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
    [coordinator animateAlongsideTransition:nil completion:^(id<UIViewControllerTransitionCoordinatorContext>  _Nonnull context) {
        [self.videoPreviewLayer.connection setVideoOrientation:[self getOrientation]];
    }];
}

但是如果UIViewController 被呈现，这个函数不会被调用（似乎是一个基于"viewWillTransitionToSize:" not called in iOS 9 when the view controller is presented modally 的已知错误）。即使解决了这个错误，还有另一个问题：方向变化不等同于尺寸变化。例如，如果一个视图显示为UIModalPresentationFormSheet，如下所示，

SecondViewController *vc = [[SecondViewController alloc] init];
vc.view.backgroundColor = [UIColor greenColor];
vc.modalPresentationStyle = UIModalPresentationFormSheet;
[self presentViewController:vc animated:true completion:nil];

iPad 横向和纵​​向模式下呈现的视图大小相同：

因此，我不能简单地使用viewWillTransitionToSize。

尝试 2

我注意到UIDeviceOrientationDidChangeNotification 没有被弃用。伟大的！我尝试注册一个通知：

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    // Some other code to set up the preview layer 
    // ...

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(deviceOrientationDidChange:)
                                                 name:UIDeviceOrientationDidChangeNotification
                                               object:nil];
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [[UIDevice currentDevice] endGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIDeviceOrientationDidChangeNotification object:nil];
}

- (void)deviceOrientationDidChange:(NSNotification *)notification {
    [self.videoPreviewLayer.connection setVideoOrientation:[self getOrientation]];
}

这是几乎工作，它是如此封闭！问题是，当我收到设备方向更改通知时，可能会启动旋转视图的动画，也可能不会。或者换句话说，如果设备已经倒置旋转但动画仍处于未决状态，则返回值[[UIApplication sharedApplication] statusBarOrientation] 可能不正确。

我不知道还能尝试什么 :( 有什么想法吗？

Answer 1

以下内容应该能够在 swift 2.1 中正确处理视频预览的方向：

override func viewWillAppear(animated: Bool) {
    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self,
        selector: Selector("deviceOrientationDidChange:"),
        name: UIDeviceOrientationDidChangeNotification,
        object: nil)
}

override func viewDidDisappear(animated: Bool) {
    NSNotificationCenter.defaultCenter().removeObserver(self)
    super.viewDidDisappear(animated)
}

func deviceOrientationDidChange(sender: AnyObject) {
    let deviceOrientation = UIDevice.currentDevice().orientation;
    switch (deviceOrientation)
    {
    case .Portrait:
       previewLayer.connection.videoOrientation = .Portrait
    case .LandscapeLeft:
       previewLayer.connection.videoOrientation = .LandscapeRight
    case .LandscapeRight:
        previewLayer.connection.videoOrientation = .LandscapeLeft
    case .PortraitUpsideDown:
       previewLayer.connection.videoOrientation = .PortraitUpsideDown
    default:
        break
    }
}