如何使用SWIFT以编程方式添加约束

Question

如何使用SWIFT以编程方式添加约束从上周开始，我一直在努力解决这个问题，但没有更进一步。好吧，所以我需要申请一些约束 以编程方式在……里面斯威夫特转到UIView使用此代码：var new_view:UIView! = UIView(frame: CGRectMake(0, 0, 100, 100));new_view.backgroundColor = UIColor.redColor();view.addSubview(new_view);var constX:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0);self.view.addConstraint(constX);var constY:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0);self.view.addConstraint(constY);var constW:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Width, multiplier: 1, constant: 0);self.view.addConstraint(constW);var constH:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Height, multiplier: 1, constant: 0);self.view.addConstraint(constH);

Answer 1

如果你想填满你的超级视图，那么我建议你用旋转的方式：

    view.translatesAutoresizingMaskIntoConstraints = false
    let attributes: [NSLayoutAttribute] = [.top, .bottom, .right, .left]
    NSLayoutConstraint.activate(attributes.map {
        NSLayoutConstraint(item: view, attribute: $0, relatedBy: .equal, toItem: view.superview, attribute: $0, multiplier: 1, constant: 0)
    })

另外，如果您需要非相等的约束，请查看iOS 9中的NSLayoutAnchor。直接使用NSLayoutConstraint通常要容易得多：

    view.translatesAutoresizingMaskIntoConstraints = false
    view.topAnchor.constraint(equalTo: view.superview!.topAnchor).isActive = true
    view.bottomAnchor.constraint(equalTo: view.superview!.bottomAnchor).isActive = true
    view.leadingAnchor.constraint(equalTo: view.superview!.leadingAnchor, constant: 10).isActive = true
    view.trailingAnchor.constraint(equalTo: view.superview!.trailingAnchor, constant: 10).isActive = true