swift3 - Xcode 模拟器不调用 TraitCollectionDidChange

Question

我正在重写traitCollectionDidChange(_)来更新我的紧凑和常规约束。当我通过旋转在设备上测试这一点时，约束得到正确更新。然而，当我尝试在模拟器中测试相同的代码时，什么也没有发生。我插入了打印语句，我可以看到在模拟器旋转时没有任何反应。这是一个错误，还是我需要为模拟器做一些特殊的事情？

提前致谢。顺便说一句，我正在使用 Xcode 8.2.1。

这是我的代码:

    private var compactConstraints: [NSLayoutConstraint] = []
    private var regularConstraints: [NSLayoutConstraint] = []
    private var sharedConstraints: [NSLayoutConstraint] = []
    ...
    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {

        super.traitCollectionDidChange(previousTraitCollection)

        if (!sharedConstraints[0].isActive) {
            // activating shared constraints
            NSLayoutConstraint.activate(sharedConstraints)
        }


        if (self.traitCollection.containsTraits(in: UITraitCollection(horizontalSizeClass: UIUserInterfaceSizeClass.compact))) {

            print("going to activate: compact")
            if regularConstraints.count > 0 && regularConstraints[0].isActive {
                NSLayoutConstraint.deactivate(regularConstraints)
            }
            // activating compact constraints
            NSLayoutConstraint.activate(compactConstraints)
        } else {
            print("going to activate: regular")
            if compactConstraints.count > 0 && compactConstraints[0].isActive {
                NSLayoutConstraint.deactivate(compactConstraints)
            }
            // activating regular constraints
            NSLayoutConstraint.activate(regularConstraints)
        }

    }

控制台输出如下:

[launch app]
`going to activate: compact`
[rotate the simulator with ⌘ arrow key]
`going to activate: compact`

基于 hoshy 问题的小更新: 我正在 iPhone 设备上使用模拟器。特别是 iPhone SE。

Answer 1

对于两个方向，

horizo​​ntalSizeClass 都是Compact。对于 iPhone SE，verticalSizeClass 对于 portrait 是 regular，对于 landscape 是 Compact。您可以更改此行

if (traitCollection.containsTraits(in: UITraitCollection(verticalSizeClass: .compact))) {

或者简单地

if traitCollection.verticalSizeClass == .compact {

---

如果您正在寻找与尺寸更改动画一起运行的动画，您还可以使用viewWillTransitionToSize:withTransitionCoordinator:。

Building an Adaptive Interface来自苹果开发者

If your Auto Layout constraints are insufficient to achieve the look you want, you can use the viewWillTransitionToSize:withTransitionCoordinator: method to make changes to your layout. You can also use that method to create additional animations to run alongside the size-change animations. For example, during an interface rotation, you might use the transition coordinator’s targetTransform property to to create a counter-rotation matrix for parts of your interface.