保持自动版式制约设备旋转工作状态 [英] Keep autolayout constraints active status on device rotation

问题描述

我注意到，当我以编程方式更新我的自动布局的限制，当我旋转屏幕的所有变化都还原。

I noticed that when I update my autolayout constraints programmatically, all changes are reverted when I rotate the screen.

重现此问题：

• 基本故事板带的UIView和2约束接口：

• Basic Storyboard interface with UIView and 2 constraints:

1. 宽度等于superview.width（乘数1）主动


2. 宽度等于superview.width（乘数1/2）禁用

创建和IBOutlet中链接这些约束条件2

Create and link these 2 constraints with IBOutlet

好像对我的错误。

你怎么想的？

截图：

故事板：

约束＃1：

约束＃2：

推荐答案

安装是指尺寸安装类，而不是有效 / 非活动

Size Classes

Installed refers to Size Classes installation, not to active/inactive.

您必须以编程方式创建另一个约束，并激活/禁用的是的之一。这是因为你不能改变一个约束的乘数（<一个href=\"http://stackoverflow.com/questions/19593641/can-i-change-multiplier-property-for-nslayoutconstraint\">Can我改变乘数属性NSLayoutConstraint？），也可以用大小鼓捣类（<一个href=\"http://stackoverflow.com/questions/27663249/activateconstraints-and-deactivateconstraints-not-persisting-after-rotation-fo\">activateConstraints:和deactivateConstraints：旋转后没有坚持在IB 创建的约束）

You must create another constraint programmatically, and activate/deactivate that one. This is because you cannot change the multiplier of a constraint (Can i change multiplier property for NSLayoutConstraint?), nor can you tinker with Size Classes (activateConstraints: and deactivateConstraints: not persisting after rotation for constraints created in IB).

有几个方法可以做到这一点。在下面的例子中，我创建您的 X1 约束的副本，具有事半功倍的或 1/2 。然后，我在两者之间切换：

There are a few ways to do so. In the example below, I create a copy of your x1 constraint, with a multiplier or 1/2. I then toggle between the two:

@IBOutlet var fullWidthConstraint: NSLayoutConstraint!
var halfWidthConstraint: NSLayoutConstraint!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    halfWidthConstraint = NSLayoutConstraint(item: fullWidthConstraint.firstItem,
        attribute: fullWidthConstraint.firstAttribute,
        relatedBy: fullWidthConstraint.relation,
        toItem: fullWidthConstraint.secondItem,
        attribute: fullWidthConstraint.secondAttribute,
        multiplier: 0.5,
        constant: fullWidthConstraint.constant)
    halfWidthConstraint.priority = fullWidthConstraint.priority
}

@IBAction func changeConstraintAction(sender: UISwitch) {
    if sender.on {
        NSLayoutConstraint.deactivateConstraints([fullWidthConstraint])
        NSLayoutConstraint.activateConstraints([halfWidthConstraint])
    } else {
        NSLayoutConstraint.deactivateConstraints([halfWidthConstraint])
        NSLayoutConstraint.activateConstraints([fullWidthConstraint])
    }
}

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测试上的的iOS 9 + X code 7 +

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