ios - 当 View Controller 在本地显示并显示警报时，控件不会变暗

Question

当我在 View Controller 上显示 UIAlertController 时，控件按预期变暗。

但是，如果同一 View Controller 本身以模态方式呈现，则警报 Controller 的显示不会使控件变暗(两个按钮保持蓝色)。

如何让呈现的 View Controller 本身正确地处理呈现，并使它的控件变暗？

Here是一个小示例项目。相关代码在MainViewController.swift中。

Answer 1

到目前为止，我的最佳解决方法是使用自定义的 UIAlertController 子类来设置 tintAdjustmentMode 及其出现/消失动画，使用 transitionCoordinator:

/// A `UIAlertController` that can udpates its presenting view controller's `tintAdjustmentMode` code as it appears and disappears
class TintAdjustingAlertController: UIAlertController {
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        animatePresentingViewTintAdjustmentMode(tintAdjustmentMode: .dimmed, forViewControllerAtKey: .from)
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        animatePresentingViewTintAdjustmentMode(tintAdjustmentMode: .automatic, forViewControllerAtKey: .to)
    }

    private func animatePresentingViewTintAdjustmentMode(tintAdjustmentMode mode: UIView.TintAdjustmentMode, forViewControllerAtKey key: UITransitionContextViewControllerKey) {
        transitionCoordinator?.animate(alongsideTransition: { context in
            if let presentingNavigationController = context.viewController(forKey: key) as? UINavigationController {
                presentingNavigationController.navigationBar.tintAdjustmentMode = mode
                presentingNavigationController.viewControllers.forEach { $0.view.tintAdjustmentMode = mode }
            } else if let presentingViewController = context.viewController(forKey: key) {
                presentingViewController.view.tintAdjustmentMode = mode
            }
            }, completion: nil)
    }
}

这行得通，但我希望不必在我的代码中使用它。仍然很想知道 a) 是否有一种简单的方法使它按预期工作，或者 b) 如果这确实是 iOS 错误，是否有更优雅的解决方法？

我还为此提交了雷达:http://www.openradar.me/radar?id=6113750608248832