如何更改已经具有高度锚点的UIView的高度? [英] How to change height of UIView that already has height anchor?

问题描述

如果我有这个用于子视图控制器:

If I have this for a child view controller:

autoCompleteViewController.view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            autoCompleteViewController.view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0),
            autoCompleteViewController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0),
            autoCompleteViewController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0),
            autoCompleteViewController.view.bottomAnchor.constraint(equalTo: googleMapViewController.view.topAnchor, constant: 0),
            autoCompleteViewController.view.heightAnchor.constraint(equalToConstant: 44.0)
        ])

如何更改其高度并更新 heightAnchor ?我已经尝试过了:

how can I change its height and update heightAnchor? I've tried this:

autoCompleteViewController
            .view
            .heightAnchor
            .constraint(equalToConstant: initialHeightAutoCompleteViewController + CGFloat(numberOfSuggestions * 45))
            .isActive = true

但是没有运气.我还尝试添加 layoutIfNeeded()和其他一些类似的方法，但是没有用.如何使用锚点更新视图高度?感谢您的回答.

but with no luck. I also tried to add layoutIfNeeded() and some other similar methods but it didn't work. How can I update view height with anchors? Thanks for your answers.

推荐答案

除了@Mukesh答案，还只是更新约束:

Additionally to @Mukesh answer is simply updating the constraint:

var heightAnchor:NSLayoutConstraint!

override func viewDidLoad() {
    super.viewDidLoad()
    heightAnchor = autoCompleteViewController.view.heightAnchor.constraint(equalToConstant:44.0)
    heightAnchor.isActive = true
}

func changeMyHeight(numberOfSuggestions: Int) {
    heightAnchor.constant = 44.0 + CGFloat(numberOfSuggestions * 45)
}

注意:

• 由于尚未实例化 autoCompleteViewController.view ，因此无法在类级别完全声明此变量.
• 您不能同时设置约束和设置 isActive = true .我总是遇到构建错误.

• You cannot fully declare this variable at the class level, as autoCompleteViewController.view is not yet instantiated.
• You cannot set up the constraint and set isActive = true at the same time. I've always gotten a build error.

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