How to implement UIVisualEffectView in UITableView with adaptive segues

问题

I would like to implement UIVisualEffectView to apply a blur effect to a view to show the view that lies behind it.

This view that should have its background blurred is a UITableViewController that is embedded in a UINavigationController, and it will either be presented in a popover on iPad or it will be presented full screen modally on iPhone, thanks to iOS 8 adaptive segues (Present as Popover). When this view controller is in a popover I want the background to blur what's underneath the popover, and when it's presented full screen I want the background to blur the previous view controller.

I have tried to implement this and have not been successful. I cannot even get the blur effect to work for the popover. I thought this code should do the trick:

//In viewDidLoad on the UITableViewController subclass:
let effectView = UIVisualEffectView(effect: UIBlurEffect(style: .Light))
effectView.frame = tableView.frame
tableView.addSubview(effectView)

I also tried adding the subview to the tableView.backgroundView, I tried setting the backgroundView to my effectView, I tried using Autolayout constraints instead of setting the frame, but nothing has worked. Can you help me accomplish the desired behavior?

An example of what I am trying to obtain:
iPad popover:

iPhone modal presentation:

回答1:

I've finally found a solution. I had to create two separate segues - one for a Popover Presentation which is called only on iPad, and the other a modal segue with Presentation Style set to Over Full Screen (that's important) for iPhone.

In the table view controller that is being presented, in viewDidLoad, this code will apply the desired blur effect (and bonus, only if they haven't disabled transparency effects):

if (!UIAccessibilityIsReduceTransparencyEnabled()) {
    tableView.backgroundColor = UIColor.clear
    let blurEffect = UIBlurEffect(style: .light)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    tableView.backgroundView = blurEffectView

    //if inside a popover
    if let popover = navigationController?.popoverPresentationController {
        popover.backgroundColor = UIColor.clear
    }

    //if you want translucent vibrant table view separator lines
    tableView.separatorEffect = UIVibrancyEffect(blurEffect: blurEffect)
}

This causes the table background to appear just like it does in the screenshots. The trick for iPhone was to ensure it's presented over the screen, while the trick for iPad was to remove the backgroundColor in the popoverPresentationController.

回答2:

A quick example to add the blur using Adaptivity:

extension ViewController: UIPopoverPresentationControllerDelegate {

 override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    // Grab the destination view controller and set the presentation delegate
    let viewController = segue.destinationViewController as UIViewController
    viewController.popoverPresentationController?.delegate = self
    viewController.presentationController?.delegate = self
  }

  // Note: Only called for FormSheet and Popover
  func adaptivePresentationStyleForPresentationController(controller: UIPresentationController) -> UIModalPresentationStyle {
    switch controller.presentedViewController {
    case let vc as PopoverViewController:
      return .None // Keep the popover in Compact screens
    default:
      return .OverFullScreen
    }
  }

  func presentationController(controller: UIPresentationController, viewControllerForAdaptivePresentationStyle style: UIModalPresentationStyle) -> UIViewController? {
    // This is a custom method on UIViewController
    controller.presentedViewController.createBlur()

    // Wrap in a Navigation Controller, the controller should add a title and bar buttons
    if !(presentedViewController is UINavigationController) {
      return UINavigationController(rootViewController: presentedViewController)
    }
  }
}

extension UIViewController {
  func createBlur(effectStyle: UIBlurEffectStyle = .Light) {
    if !UIAccessibilityIsReduceTransparencyEnabled() {
      view.backgroundColor = UIColor.clearColor()

      let blurView = UIVisualEffectView(effect: UIBlurEffect(style: effectStyle))
      blurView.autoresizingMask = UIViewAutoresizing.FlexibleHeight | UIViewAutoresizing.FlexibleWidth
      blurView.frame = view.bounds

      view.insertSubview(blurView, atIndex: 0)
    }
  }
}

extension UITableViewController {
  override func createBlur(effectStyle: UIBlurEffectStyle = defaultBlurEffectStyle) {
    if !UIAccessibilityIsReduceTransparencyEnabled() {
      tableView.backgroundColor = UIColor.clearColor()

      let blurEffect = UIBlurEffect(style: effectStyle)      
      tableView.backgroundView = UIVisualEffectView(effect: blurEffect)
      tableView.separatorEffect = UIVibrancyEffect(forBlurEffect: blurEffect)
    }
  }
}

回答3:

Slightly late to the table with this one, but the best solution for me (in ios8 +), was to take a UIVisualEffectView in the Storyboard and make it the root view of my ViewController. Then add my tableview to that

To find the Visual Effect View, go to the Components Picker (not sure what thats called) on the bottom right hand side and search for VisualEffectView

This seems like a much easier way to go about it, and falls in line with Apple's recommendation to do as much on the Storyboard as possible

回答4:

A small change for IOS 10 Swift 3

if #available(iOS 10.0, *) {
        let blurEffect = UIBlurEffect(style: .prominent)
        let blurEffectView = UIVisualEffectView(effect: blurEffect)
        groupTable.backgroundView = blurEffectView

    } else {
        let blurEffect = UIBlurEffect(style: .dark)
        let blurEffectView = UIVisualEffectView(effect: blurEffect)
        groupTable.backgroundView = blurEffectView

    }

来源：https://stackoverflow.com/questions/24424165/how-to-implement-uivisualeffectview-in-uitableview-with-adaptive-segues