Autolayout Programatic Sizing Woes：无法调整Superview的大小

Question

如果我在IB中定义约束，我仍然可以调整包含子视图的窗口的大小。

<小时/>

所有其他约束相同，但是左，右和底。

<小时/> 当我尝试在代码中执行此操作时，我不能再在运行时手动调整superview（NSWindow）的大小，也不能最大化它：

class ViewController: NSViewController {

    @IBOutlet var box : NSBox!

    func matchAttribute(attribute: NSLayoutAttribute, view: NSView, superview: NSView) {
        var constraint = NSLayoutConstraint(item: view, attribute: attribute, relatedBy: NSLayoutRelation.Equal, toItem: superview, attribute: attribute, multiplier: 1, constant: 0)
        constraint.priority = 1000
        superview.addConstraint(constraint)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        self.matchAttribute(NSLayoutAttribute.Top, view: self.box, superview: self.box.superview!)
        self.matchAttribute(NSLayoutAttribute.Trailing, view: self.box, superview: self.box.superview!)
        self.matchAttribute(NSLayoutAttribute.Leading, view: self.box, superview: self.box.superview!)
        self.matchAttribute(NSLayoutAttribute.Bottom, view: self.box, superview: self.box.superview!)
    }
}

我必须采取哪些措施才能以编程方式获得相同的Autolayout行为？

Answer 1

因为您没有在Interface Builder中向框中添加任何约束，所以在加载它时，它被认为具有不明确的布局。为了消除这种歧义，Cocoa自动添加了一些约束：

override func viewDidLoad() {
    super.viewDidLoad()

    println(view.constraints)
    //-> <NSIBPrototypingLayoutConstraint:0x600000082e40 'IB auto generated at build time for view with fixed frame' H:|-(0)-[NSBox:0x100716940'This Is A Box'](LTR)   (Names: '|':AutoStack.PPView:0x100516120 )>
    //-> <NSIBPrototypingLayoutConstraint:0x600000082ee0 'IB auto generated at build time for view with fixed frame' V:|-(0)-[NSBox:0x100716940'This Is A Box']   (Names: '|':AutoStack.PPView:0x100516120 )>
    //-> <NSIBPrototypingLayoutConstraint:0x600000082f80 'IB auto generated at build time for view with fixed frame' H:[NSBox:0x100716940'This Is A Box'(480)]>
    //-> <NSIBPrototypingLayoutConstraint:0x600000083020 'IB auto generated at build time for view with fixed frame' V:[NSBox:0x100716940'This Is A Box'(270)]>
}

你会注意到最后两个约束的组合效果是固定盒子的宽度和高度 - 这就是你不能调整窗口大小的原因，因为这样做会违反这些约束。

要获得所需的效果，首先需要删除这些自动生成的约束：

override func viewDidLoad() {
    super.viewDidLoad()

    view.removeConstraints(view.constraints)
    // Forbid Cocoa from automatically adding its own constraints to this view 
    view.translatesAutoresizingMaskIntoConstraints = false

    // Note that in your implementation you are needlessly typing <self>
    matchAttribute(NSLayoutAttribute.Top, view: box, superview: box.superview!)
    matchAttribute(NSLayoutAttribute.Trailing, view: box, superview: box.superview!)
    matchAttribute(NSLayoutAttribute.Leading, view: box, superview: box.superview!)
    matchAttribute(NSLayoutAttribute.Bottom, view: box, superview: box.superview!)
}