调整UIView的大小限制.迅速 [英] Resize constraints for UIView. swift

问题描述

我在屏幕上有两个自定义UIView.UIViewOne占据了75％的屏幕，UIViewTwo占据了25％的屏幕.我需要单击UIViewTwo，调整它的大小以使其第二个越来越大.我也知道这需要使用约束来完成，但是我不知道如何做.请告诉我如何解决这个问题.

I have two custom UIViews on the screen. UIViewOne occupies 75% of the screen, and UIViewTwo 25%. I need to click on UIViewTwo, resize it to make the second bigger and smaller first. I also know that this needs to be done using constraints, but I don't know how. Please tell me how to solve this problem.

推荐答案

一种方法是向 view1 添加两个高度限制并更改其优先级，

One approach is to add two Height constraints to view1 and change their Priority,

• 将高度限制添加为75％(乘数= 0.75 )
• 将其优先级设置为 999
• 将高度限制添加为25％(乘数= 0.25 )
• 将其优先级设置为 998
• 将 view2 的顶部约束到 view1 的底部.

• add a Height constraint at 75% (multiplier = 0.75)
• set its Priority to 999
• add a Height constraint at 25% (multiplier = 0.25)
• set its Priority to 998
• constraint the Top of view2 to the bottom of view1.

开始时，高度限制为75％优先于25％限制... 999 大于 998 .当您点击 view2 时，将75％约束的优先级"更改为 997 .现在 997 小于 998 ，因此25％的约束获得了优先级.

At the start, the 75% Height constraint will have priority over the 25% constraint ... 999 is greater than 998. When you tap view2, change the 75% constraint's Priority to 997. Now 997 is less than 998, so the 25% constraint gets the priority.

由于 view2 的顶部被限制在 view1 的底部，所以 view2 会自动调整大小.

Since view2's top is constrained to view1's bottom, view2 will automatically resize.

以下是您可以按原样运行的示例(只需将其分配给视图控制器...就不需要 IBOutlet 或 IBAction 连接):

Here is an example you can run as-is (just assign it to a view controller... no IBOutlet or IBAction connections needed):

class PercentViewController: UIViewController {

    let view1: UIView = {
        let v = UIView()
        v.backgroundColor = .red
        return v
    }()

    let view2: UIView = {
        let v = UIView()
        v.backgroundColor = .green
        return v
    }()

    var topView75: NSLayoutConstraint!
    var topView25: NSLayoutConstraint!

    override func viewDidLoad() {
        super.viewDidLoad()

        // we're using auto-layout
        view1.translatesAutoresizingMaskIntoConstraints = false
        view2.translatesAutoresizingMaskIntoConstraints = false

        // add views
        view.addSubview(view1)
        view.addSubview(view2)

        // respect safe area
        let g = view.safeAreaLayoutGuide

        // create "75% height constraint"
        topView75 = view1.heightAnchor.constraint(equalTo: g.heightAnchor, multiplier: 0.75)
        // create "25% height constraint"
        topView25 = view1.heightAnchor.constraint(equalTo: g.heightAnchor, multiplier: 0.25)

        // give 75% constraint higher priority than 25% constraint
        topView75.priority = UILayoutPriority(rawValue: 999)
        topView25.priority = UILayoutPriority(rawValue: 998)

        NSLayoutConstraint.activate([

            // view1 constrained Top, Leading, Trailing (to safe-area)
            view1.topAnchor.constraint(equalTo: g.topAnchor),
            view1.leadingAnchor.constraint(equalTo: g.leadingAnchor),
            view1.trailingAnchor.constraint(equalTo: g.trailingAnchor),

            // view2 constrained Bottom, Leading, Trailing (to safe-area)
            view2.bottomAnchor.constraint(equalTo: g.bottomAnchor),
            view2.leadingAnchor.constraint(equalTo: g.leadingAnchor),
            view2.trailingAnchor.constraint(equalTo: g.trailingAnchor),

            // view2 Top constrained to view1 Bottom
            view2.topAnchor.constraint(equalTo: view1.bottomAnchor),

            // activate both Height constraints
            topView75,
            topView25,

        ])

        // create tap gesture recognizers
        let tap1 = UITapGestureRecognizer(target: self, action: #selector(view1Tapped(_:)))
        let tap2 = UITapGestureRecognizer(target: self, action: #selector(view2Tapped(_:)))

        // add to the views
        view1.addGestureRecognizer(tap1)
        view2.addGestureRecognizer(tap2)

    }

    @objc func view1Tapped(_ sender: Any) -> Void {
        // view1 tapped, so give 75% constraint a higher priority than 25% constraint
        topView75.priority = UILayoutPriority(rawValue: 999)
        // 0.3-second animation
        UIView.animate(withDuration: 0.3) {
            self.view.layoutIfNeeded()
        }
    }

    @objc func view2Tapped(_ sender: Any) -> Void {
        // view2 tapped, so give 25% constraint a higher priority than 75% constraint
        topView75.priority = UILayoutPriority(rawValue: 997)
        // 0.3-second animation
        UIView.animate(withDuration: 0.3) {
            self.view.layoutIfNeeded()
        }
    }

}

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