ios - 不要在水平紧凑的环境中折叠 UISplitViewController

Question

UISplitViewController 的默认行为是当它从水平规则转换到水平紧凑环境时折叠。是否有可能以某种方式覆盖它？

由于某些设计解决方案，我希望 splitView 始终展开。我没有在 UISplitViewController 的文档中找到解决方案:属性 collapsed 是只读的，委托(delegate)方法仅用于“如何折叠”，而不用于“一点都不崩溃”。我正在使用 iOS9 SDK。

Answer 1

我想通了。文档指出:

The split view controller determines the arrangement of its child view controllers based on the available space. In a horizontally regular environment, the split view controller presents its view controllers side-by-side whenever possible. In a horizontally compact environment, the split view controller acts more like a navigation controller, displaying the primary view controller initially and pushing or popping the secondary view controller as needed.

因此 splitView 在 Compact 水平环境中总是会折叠，在 Regular 中会展开。解决方法就是在我们要展开的时候告诉splitView它有Regular horizo​​ntal environment。思路取自WWDC 2014 Video “使用 UIKit 构建自适应应用程序”。不幸的是，sample code他们在视频中提到的不包括这种情况。但我们的想法是为 SplitViewController 创建包含 ViewController，我们可以在其中使用方法 setOverrideTraitCollection:forChildViewController:

覆盖 SplitViewController 的特征集合

@implementation ContainingViewController

- (instancetype)initWithNibName:(nullable NSString *)nibNameOrNil bundle:(nullable NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nil bundle:nil];
    if (self)
    {
        _splitViewController = [[UISplitViewController alloc] initWithNibName:nil bundle:nil];
        _splitViewController.viewControllers = <view controllers>;

        [self addChildViewController:_splitViewController];
        [self.view addSubview:_splitViewController.view];

        UITraitCollection *horizontallyRegularTraitCollection = [UITraitCollection traitCollectionWithHorizontalSizeClass:UIUserInterfaceSizeClassRegular];
        [self setOverrideTraitCollection:horizontallyRegularTraitCollection forChildViewController:_splitViewController];
    }
    return self;
}

通过这段代码，SplitViewController 将始终具有 Regular 水平特征集合，从而扩展。