公认的答案是正确的，但这里缺少一个重要的步骤，如果这个视图-您想要模糊的背景-是使用

[self presentViewController:vc animated:YES completion:nil]

默认情况下，这将抵消模糊，因为UIKit删除演示者的视图，这实际上是模糊的。为了避免这种删除，将这一行添加到前一行之前

vc。modalPresentationStyle = UIModalPresentationOverFullScreen;

或者使用其他Over样式。

这是乔伊回答的重要补充

这适用于你想用UINavigationController呈现一个模糊背景的UIViewController的情况。

// suppose you've done blur effect with your presented view controller
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController];

// this is very important, if you don't do this, the blur effect will darken after view did appeared
// the reason is that you actually present navigation controller, not presented controller
// please note it's "OverFullScreen", not "OverCurrentContext"
nav.modalPresentationStyle = UIModalPresentationOverFullScreen;

UIViewController *presentedViewController = [[UIViewController alloc] init]; 
// the presented view controller's modalPresentationStyle is "OverCurrentContext"
presentedViewController.modalPresentationStyle = UIModalPresentationOverCurrentContext;

[presentingViewController presentViewController:nav animated:YES completion:nil];

享受吧!

苹果为UIImage类提供了一个名为UIImage+ImageEffects.h的扩展。在这个类中，您可以使用所需的方法来模糊视图

以下是Swift 2.0解决方案的代码，已经在接受的答案中提供:

    //only apply the blur if the user hasn't disabled transparency effects
    if !UIAccessibilityIsReduceTransparencyEnabled() {
        self.view.backgroundColor = UIColor.clearColor()

        let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Dark)
        let blurEffectView = UIVisualEffectView(effect: blurEffect)
        //always fill the view
        blurEffectView.frame = self.view.bounds
        blurEffectView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]

        self.view.addSubview(blurEffectView) //if you have more UIViews, use an insertSubview API to place it where needed
    } else {
        self.view.backgroundColor = UIColor.blackColor()
    }

斯威夫特4:

你也可以使用容器视图，它可以让你获得一个免费的视图控制器(你可以从通常的对象面板/库中获得容器视图)。

步骤:

有一个视图(图片中的ViewForContainer)持有这个容器视图，当容器视图的内容显示时，使其暗淡。连接第一个视图控制器内部的出口

当第一个VC加载时隐藏这个视图

当按钮点击此处输入图像描述时取消隐藏

当容器视图内容显示时，要使该视图变暗，将视图背景设置为黑色，不透明度设置为30%

我已经在其他Stackoverflow问题中添加了popview视图创建的答案 https://stackoverflow.com/a/49729431/5438240

func blurBackgroundUsingImage(image: UIImage)
{
    var frame                   = CGRectMake(0, 0, self.view.frame.width, self.view.frame.height)
    var imageView               = UIImageView(frame: frame)
    imageView.image             = image
    imageView.contentMode       = .ScaleAspectFill
    var blurEffect              = UIBlurEffect(style: .Light)
    var blurEffectView          = UIVisualEffectView(effect: blurEffect)
    blurEffectView.frame        = frame
    var transparentWhiteView    = UIView(frame: frame)
    transparentWhiteView.backgroundColor = UIColor(white: 1.0, alpha: 0.30)
    var viewsArray              = [imageView, blurEffectView, transparentWhiteView]

    for index in 0..<viewsArray.count {
        if let oldView = self.view.viewWithTag(index + 1) {
            var oldView         = self.view.viewWithTag(index + 1)
            // Must explicitly unwrap oldView to access its removeFromSuperview() method as of Xcode 6 Beta 5
            oldView!.removeFromSuperview()
        }
        var viewToInsert        = viewsArray[index]
        self.view.insertSubview(viewToInsert, atIndex: index + 1)
        viewToInsert.tag        = index + 1
    }
}