iOS - Split View Controller - 如何从主视图 Controller 内部获取指向详细 View Controller 的指针(引用)？

Question

iOS - Split View Controller - 如何从主视图 Controller (左侧较小的 Controller )内部获取指向详细 View Controller (右侧较大的 Controller )的指针(引用)？

我的直觉告诉我 Main Split View Controller 应该引用 Detail View Controller 和我自己的 Master View Controller，但我不知道如何获取它。

有什么想法吗？

Answer 1

Split View Controller 确实通过viewControllers 属性引用了它们的主视图 Controller 和详细 View Controller 。

在 iOS 7.x 及以下版本中，viewControllers 数组中应该正好有两个 View Controller 对象。第一个对象是主视图 Controller ，第二个对象是详细 View Controller 。

在 iOS 8.0 及更高版本中，viewControllers 数组中至少有一个 View Controller 对象——主(或“主要”) View Controller 。如果第二个 View Controller 对象在数组中，那么它就是细节(或“辅助”) View Controller 。当 Split View Controller 折叠时，只有主视图 Controller 在这个数组中，当展开时它将包含主视图 Controller 和详细 View Controller 。

您可以使用所有 View Controller 的 splitViewController 属性来获取您的 Split View Controller ，然后使用 viewControllers 属性访问您的主视图 Controller 或详细 View Controller ，像这样:

swift :

let masterVC = self.splitViewController?.viewControllers.first
let detailVC = (self.splitViewController?.viewControllers.count > 1) ? self.splitViewController?.viewControllers[1] : nil

objective-C :

UIViewController *masterVC = [self.splitViewController.viewControllers firstObject];
UIViewController *detailVC;
if (self.splitViewController.viewControllers.count > 1) {
    detailVC = self.splitViewController.viewControllers[1];
}

splitViewController 属性通过在 View Controller 层次结构中向上移动并尝试找到调用 View Controller 所在的任何 Split View Controller 来工作。如果 View Controller 不在 Split View Controller 中，则该属性为 nil。它与 navigationController 和 tabBarController View Controller 属性的工作原理相同。

您可以在 UISplitViewController 上使用 Swift 中的扩展(或 Objective-C 中的类别)使主视图 Controller 和详细 View Controller 更易于访问，就像这样(替换所有 xx_ 如果您使用的是 Objective-C，请使用您自己的前缀):

swift :

extension UISplitViewController {
    var primaryViewController: UIViewController? {
        return self.viewControllers.first
    }

    var secondaryViewController: UIViewController? {
        return self.viewControllers.count > 1 ? self.viewControllers[1] : nil
    }
}

objective-C :

// UISplitViewController+ChildViewControllerAccess.h
@interface UISplitViewController (ChildViewControllerAccess)

@property (nonatomic, readonly) UIViewController *xx_primaryViewController;
@property (nonatomic, readonly) UIViewController *xx_secondaryViewController;

@end

// UISplitViewController+ChildViewControllerAccess.m
@implementation UISplitViewController (ChildViewControllerAccess)

- (UIViewController *)xx_primaryViewController
{
    return self.viewControllers.firstObject;
}

- (UIViewController *)xx_secondaryViewController
{
    return self.viewControllers.count > 1 ? self.viewControllers[1] : nil;
}

@end

然后您可以像这样使用这些属性:

swift :

func someFunctionInSomeViewControllerClass {
    // Get the primary and secondary view controllers if
    // this view controller is in a split view controller.
    // These will be nil if this view controller is not a
    // descendant of a split view controller.
    var primaryVC = self.splitViewController?.primaryViewController
    var secondaryVC = self.splitViewController?.secondaryViewController

    // Do something with them
    primaryVC?.title = "This is the primary VC"
    secondaryVC?.title = "This is the secondary VC"
}

objective-C :

#import "UISplitViewController+ChildViewControllerAccess.h"

[...]

- (void)someMethodInSomeViewControllerClass
{
    // Get the primary and secondary view controllers if
    // this view controller is in a split view controller.
    // These will be nil if this view controller is not a
    // descendant of a split view controller.
    UIViewController *primaryVC = self.splitViewController.xx_primaryViewController;
    UIViewController *secondaryVC = self.splitViewController.xx_secondaryViewController;

    // Do something with them
    primaryVC.title = @"This is the primary VC";
    secondaryVC.title = @"This is the secondary VC";
}