自定义模态演示中的 UIBlurEffect

Question

我目前正在使用自定义UIPresentationController 在屏幕的三分之一上展示一个视图控制器。在我的UIPresentationController 中，我将presentedViewController 包裹在几个视图中以获得圆角和阴影（就像在Apple 的自定义过渡示例应用程序中一样）。我最近在presentedViewController 层次结构中添加了带有UIBlurEffect 的UIVisualEffectView，但它显示得很奇怪。视图现在是半透明的，但不是模糊的。

我认为这是因为正确应用了模糊效果，但因为它是模态演示，它看不到后面的视图，因此无法模糊它。有什么想法吗？这是相关的代码 override func presentationTransitionWillBegin()

    // Wrap the presented view controller's view in an intermediate hierarchy
    // that applies a shadow and rounded corners to the top-left and top-right
    // edges.  The final effect is built using three intermediate views.
    //
    // presentationWrapperView              <- shadow
    //   |- presentationRoundedCornerView   <- rounded corners (masksToBounds)
    //        |- presentedViewControllerWrapperView
    //             |- presentedViewControllerView (presentedViewController.view)
    //
    // SEE ALSO: The note in AAPLCustomPresentationSecondViewController.m.


    let presentationWrapperView = UIView(frame: frameOfPresentedViewInContainerView)
    presentationWrapperView.layer.shadowOpacity = 0.44
    presentationWrapperView.layer.shadowRadius = 13
    presentationWrapperView.layer.shadowOffset = CGSize(width: 0, height: -6)
    self.presentationWrappingView = presentationWrapperView

    // presentationRoundedCornerView is CORNER_RADIUS points taller than the
    // height of the presented view controller's view.  This is because
    // the cornerRadius is applied to all corners of the view.  Since the
    // effect calls for only the top two corners to be rounded we size
    // the view such that the bottom CORNER_RADIUS points lie below
    // the bottom edge of the screen.
    let presentationRoundedCornerView = UIView(frame: UIEdgeInsetsInsetRect(presentationWrapperView.bounds, UIEdgeInsets(top: 0, left: 0, bottom: -CORNER_RADIUS, right: 0)))
    presentationRoundedCornerView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    presentationRoundedCornerView.layer.cornerRadius = CORNER_RADIUS
    presentationRoundedCornerView.layer.masksToBounds = true

    // To undo the extra height added to presentationRoundedCornerView,
    // presentedViewControllerWrapperView is inset by CORNER_RADIUS points.
    // This also matches the size of presentedViewControllerWrapperView's
    // bounds to the size of -frameOfPresentedViewInContainerView.
    let presentedViewControllerWrapperView = UIView(frame: UIEdgeInsetsInsetRect(presentationRoundedCornerView.bounds, UIEdgeInsets(top: 0, left: 0, bottom: CORNER_RADIUS, right: 0)))
    presentedViewControllerWrapperView.autoresizingMask = [.flexibleWidth, .flexibleHeight]

    let blurWrapperView = UIVisualEffectView(effect: UIBlurEffect(style: .light))
    blurWrapperView.autoresizingMask =  [.flexibleWidth, .flexibleHeight]
    blurWrapperView.frame = presentedViewControllerWrapperView.bounds

    // Add presentedViewControllerView -> presentedViewControllerWrapperView.
    presentedViewControllerView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    presentedViewControllerView.frame = blurWrapperView.bounds
    blurWrapperView.contentView.addSubview(presentedViewControllerView)

    presentedViewControllerWrapperView.addSubview(blurWrapperView)
    // Add presentedViewControllerWrapperView -> presentationRoundedCornerView.
    presentationRoundedCornerView.addSubview(presentedViewControllerWrapperView)

    // Add presentationRoundedCornerView -> presentationWrapperView.
    presentationWrapperView.addSubview(presentationRoundedCornerView)

Answer 1

正如我在上面的评论中所说，根据我的经验，使用UIPresentationController 的presentationStyle 属性可以定义一旦发生这种情况，如何处理呈现的视图背后的视图。有关它的更多信息，请参阅here。该属性本身的类型为UIModalPresentationStyle，您可以看到它的可用值here。

在我看来，overCurrentContext 似乎是您想要的值。来自 Apple 的文档：

演示结束时，演示内容下方的视图不会从视图层次结构中删除。因此，如果呈现的视图控制器没有用不透明的内容填充屏幕，则底层内容会显示出来。

在我看来，这意味着您的模糊视图将会有一些需要模糊的东西。

更新

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此外，您也可以尝试this，即使 Apple 的文档似乎已关闭。我认为该属性的默认值是true 而不是那里提到的false。

Answer 2

我假设您正在模拟器上进行测试，对吧？如果是这样，请确保检查模拟器的 Graphic's Quality Override 设置并将其设置为 High Quality。这应该对你有用。