ios - UISplitViewController 的 preferredDisplayMode : incorrect behavior

Question

我有一个主从应用程序(我使用 Xcode 模板创建它，然后稍微修改了它)，我试图设置 UISplitViewController 的 preferredDisplayMode 属性以获得此行为:

UISplitViewControllerDisplayMode.PrimaryOverlay: The primary view controller is layered on top of the secondary view controller, leaving the secondary view controller partially visible.

所以主视图 Controller 最初应该位于详细 View Controller 之上，并且应该可以将其关闭。我在 application:didFinishLaunchingWithOptions: 中更改了这个属性，这是完整的代码:

 
// Inside application:didFinishLaunchingWithOptions:
// Override point for customization after application launch.
let rootViewController = window!.rootViewController as! UINavigationController
// The root view controller is a navigation controller that contains the split view controller
let splitViewController = rootViewController.viewControllers[0] as! UISplitViewController<p></p>

<p>let navigationController = splitViewController.viewControllers[splitViewController.viewControllers.count-1] as! UINavigationController
navigationController.topViewController.navigationItem.leftBarButtonItem = splitViewController.displayModeButtonItem()
splitViewController.delegate = self</p>

<p>splitViewController.preferredPrimaryColumnWidthFraction = 0.4
splitViewController.maximumPrimaryColumnWidth = 600
<b>splitViewController.preferredDisplayMode = .PrimaryOverlay</b></p>

<p>return true
</p>

I have two problems: first, that's not the behavior that I obtain. The master view controller is hidden when the application launches, and if I click on the left bar button item to show the master, it rapidly appears and then disappears again. If I click it another time it appears without disappearing.
Second, I get a warning in the console:

2015-06-30 12:06:26.613 Presidents[29557:857547] Unbalanced calls to begin/end appearance transitions for <UINavigationController: 0x7b8be610>.

但我的代码中没有转换。

PS:摘自 D. Mark、J. Nutting、K. Topley、F. Olsson、J. LaMarche 所著的“使用 Swift 开始电话开发”一书，第 11 章。

Answer 1

我在我的 iPad 应用程序中使用了它。在主视图 Controller 中:

override func viewDidLoad() {
    super.viewDidLoad()

    splitViewController?.delegate = self

    let rect: CGRect = UIScreen.mainScreen().bounds
    if rect.height > rect.width {
        // am in portrait: trick to force the master view to open
        self.splitViewController?.preferredDisplayMode = .PrimaryOverlay
    }

然后:

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    self.splitViewController?.preferredDisplayMode = .Automatic

现在正在尝试找出如何使用 iPhone 应用程序来实现...编辑:啊，见this previous answer