Layout issues when presenting a view controller with UIModalPresentationStyleCurrentContext

问题

I ran into a problem having to do with UISplitViewController and modal view controllers on the iPad, so I tried to reproduce the issue in a small project to see if I could figure out what was going on. Unfortunately, the problem seems to still be occurring, but I can't figure out why.

I've included a very small, complete Swift program below that reproduces the problem. Basically, if you run that code in a new Swift iOS project on the iPad, you'll see the following behavior:

The app will start with the following UI:

If I tap Present, a new modal controller will present over the detail side of the split controller. If I tap Dismiss on that modal controller, I'll return to the same initial interface and all is well.

However, if I tap Present, then tap Present on the modal controller that appears (so I have two modal controllers over the original details view), and then dismiss the top one, the RightViewController takes over the entire screen, eliminating the split view controller:

I've been banging my head against this all afternoon. Is there something I'm missing?

Here is the complete source for the example application:

import UIKit

class RightController: UIViewController {
    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        self.title = "Right"
    }

    required init(coder aDecoder: NSCoder) {
      fatalError("init(coder:) has not been implemented")
    }

    override func loadView() {
        super.loadView()

        let label = UILabel(frame: CGRect(x: 0, y: 100, width: 100, height: 20))
        label.text = "Top Left"
        self.view.addSubview(label)

        let presButton = UIBarButtonItem(title: "Present", style: .Plain, target: self, action: Selector("present:"))

        self.navigationItem.rightBarButtonItem = presButton
        self.navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Dismiss", style: .Plain, target: self, action: Selector("dismiss:"))
    }

    func dismiss(sender: AnyObject) {
        self.dismissViewControllerAnimated(true, completion: nil)
    }

    func present(sender: AnyObject) {
        let rc = RightController()
        let nav = UINavigationController(rootViewController: rc)
        nav.modalPresentationStyle = .CurrentContext
        self.presentViewController(nav, animated: true, completion: nil)
    }
}

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, UISplitViewControllerDelegate {
    var window: UIWindow?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        let splitViewController = UISplitViewController()
        splitViewController.delegate = self

        let nav1 = UINavigationController(rootViewController: UIViewController())
        nav1.title = "Left"

        let nav2 = UINavigationController(rootViewController: RightController())

        splitViewController.viewControllers = [nav1, nav2]
        self.window!.rootViewController = splitViewController

        return true
    }
}

extension AppDelegate: UISplitViewControllerDelegate {
    func splitViewController(svc: UISplitViewController, shouldHideViewController vc: UIViewController, inOrientation orientation: UIInterfaceOrientation) -> Bool {
        return false
    }
}

EDIT: Cycling through the device's orientations causes the split view controller to redraw itself correctly, at least until Dismiss is pressed again.

EDIT: I can also get this to work if I use the new .OverCurrentContext presentation style in iOS 8. However, I can't drop compatibility with iOS 7, so I need a different solution.

回答1:

I have a solution that works although I will be the first to admit, it does feel a little hacky. I think a big part of your issue stems from a change in .CurrentContext and after some testing I found that it functions differently for iOS 7 and 8+. So everything works expectedly if you choose the proper style based on the iOS version:

var presStyle: UIModalPresentationStyle = (UIDevice.currentDevice().systemVersion as NSString).integerValue == 7 ? .CurrentContext : .OverCurrentContext
nav.modalPresentationStyle = presStyle

来源：https://stackoverflow.com/questions/29242286/layout-issues-when-presenting-a-view-controller-with-uimodalpresentationstylecur

标签

ios

ipad

swift

uisplitviewcontroller

modalviewcontroller