以编程方式显示和隐藏容器UIView及其子视图

Question

我有一个标签和一个按钮并排，如下所示：

这是由以下代码创建的：

private func addViewBack() {
    myLabel.translatesAutoresizingMaskIntoConstraints = false
    myLabel.text = "Show my label"

    myButton.addTarget(self, action: #selector(pressed), for: .touchUpInside)
    myButton.setTitleColor(UIColor.lightGray, for: UIControl.State.normal)
    myButton.translatesAutoresizingMaskIntoConstraints = false
    myButton.setTitle("Button", for: .normal)
    myButton.clipsToBounds = true

    containerView.backgroundColor = .red
    containerView.addSubview(myLabel)
    containerView.translatesAutoresizingMaskIntoConstraints = false
    containerView.addSubview(myButton)

    containerView.addConstraint(NSLayoutConstraint(item: myButton, attribute: .centerY, relatedBy: .equal, toItem: myLabel, attribute: .centerY, multiplier: 1, constant: 0))
    containerView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-8-[myLabel]-8-|", options: [], metrics: nil, views: ["myLabel":myLabel]))
    containerView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-8-[myLabel]", options: [], metrics: nil, views: ["myLabel":myLabel]))
    containerView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:[myButton]-8-|", options: [], metrics: nil, views: ["myButton":myButton]))
    containerView.layoutIfNeeded()

    self.view.addSubview(containerView)

    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:[topView]-100-[containerView]", options: [], metrics: nil, views: ["containerView":containerView,"topView":viewTop]))
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-8-[containerView]-8-|", options: [], metrics: nil, views: ["containerView":containerView]))
    self.view.layoutIfNeeded()
}

我有按下按钮时显示和隐藏容器视图的显示和隐藏按钮，如下所示：

@IBAction func show(_ sender: Any) {

    if let constraint = (containerView.constraints.filter{$0.firstAttribute == .height}.first) {
        constraint.isActive = false
    }

    containerView.layoutIfNeeded()
}

@IBAction func hide(_ sender: Any) {
    containerView.heightAnchor.constraint(equalToConstant: 0).isActive = true
    containerView.layoutIfNeeded()

}

当使用隐藏动作时，按钮永远不会被隐藏，我最终会得到这样的结果：

当我添加以下内容时，它可以工作：

@IBAction func hide(_ sender: Any) {
    containerView.heightAnchor.constraint(equalToConstant: 0).isActive = true
    myButton.heightAnchor.constraint(equalToConstant: 0).isActive = true
    containerView.layoutIfNeeded()

}

当我按下show动作时，按钮永远不会再次出现，如下所示：

如何以编程方式使用自动布局非常简单地在容器视图中显示和隐藏元素？

Answer 1

不要使容器视图高度约束处于活动/非活动状态，而是将其常量更改为零以隐藏容器视图。如果它的clipsToBounds为真，那也会隐藏内容。