Swift UISplitViewController - unable to present master view before detail view (iOS 14, Xcode 12.4)

Question

I am having this issue where I am using a UISplitViewController MainSplitVC, and I am unable to present the master view controller over the detail view controller. Basically, when testing this on an iPad, I want the master and detail VC to be visible side by side, but on an iPhone (portrait mode), I want only the master VC. Currently, this works on iPad, but on an iPhone in portrait mode, Swift is showing the detail view controller first, and I have to click the back button in the navigation bar to return to the master view controller.

I have tried every possible approach that I could think of. For instance, I created a class for the Split View Controller, MainSplitVC, where I subclass UISplitViewController and UISplitViewControllerDelegate. Then, in viewDidLoad(), I set the preferred display mode to oneBesideSecondary (since allVisible was replaced by that according to Xcode). I also include the function collapseSecondary() to always collapse back to the master view controller.

class MainSplitVC: UISplitViewController, UISplitViewControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
        print("viewDidLoad called")
        self.preferredDisplayMode = UISplitViewController.DisplayMode.oneBesideSecondary
    }

    func splitViewController(
             _ splitViewController: UISplitViewController,
             collapseSecondary secondaryViewController: UIViewController,
             onto primaryViewController: UIViewController) -> Bool {
        print("collapseSecondary called")
        return true
    }
    
}

I have consulted many other posts regarding this issue, and all the posts indicate that using the collapseSecondary() function and setting preferredDisplayMode to oneBesideSecondary or allVisible should do the job. However, none of this is working. What's more is that the collapseSecondary() function is not even being called, even though I included UISplitViewControllerDelegate in the class header.

Could anyone clarify if I made any mistakes in the code below? When the app opens, I just want the master view controller to be shown; the detail view controller is simply a blank view controller that changes to another when something in the tableview of the master view controller is clicked.

The links I used for reference were as follows:

Thanks!

EDIT 2/3/21: I've resolved the issue. I instead extended SceneDelegate under UISplitViewControllerDelegate and included the following function:

func splitViewController(_ svc: UISplitViewController, topColumnForCollapsingToProposedTopColumn proposedTopColumn: UISplitViewController.Column) -> UISplitViewController.Column {
    return .primary
}

The collapseSecondary function didn't work apparently because there is a bug where "Interface Builder doesn’t allow creating a classic style UISplitViewController. (65966010) (FB8107534)", so I get the error message "Skipping delegate callback, splitViewController:collapseSecondaryViewController:ontoPrimaryViewController:. Unsupported for UISplitViewController style DoubleColumn".

Thanks!

Felix Marianayagam Felix Marianayagam · Accepted Answer · 2021-02-03T07:15:03

Returning .primary should solve your issue.

@available(iOS 14.0, *)
public func splitViewController(_ svc: UISplitViewController, topColumnForCollapsingToProposedTopColumn proposedTopColumn: UISplitViewController.Column) -> UISplitViewController.Column {
    return .primary
}

[From Documentation] Asks the delegate to provide the column to display after the split view interface collapses.

When the split view controller transitions from a horizontally regular to a horizontally compact size class, it calls this method and asks you for the column to display when that transition is complete. Use this method to customize the view controller you’re collapsing to.

Swift UISplitViewController - unable to present master view before detail view (iOS 14, Xcode 12.4)

1 Answers