动态限制按钮在屏幕的右下角 - Swift

Question

如何从背景视图中动态限制下面的按钮，使其位于屏幕的右下角？

下面的代码是错误的，但我想我需要做这样的事情？

let constraints = [
            button.topAnchor.constraint(equalTo: backView.topAnchor),
            button.leftAnchor.constraint(equalTo: backView.leftAnchor, constant: -40),
            button.bottomAnchor.constraint(equalTo: backView.bottomAnchor),
            button.rightAnchor.constraint(equalTo: backView.rightAnchor, constant: -40)
        ]
        
        NSLayoutConstraint.activate(constraints)

Answer 1

这是用于添加视图右下角按钮的代码

        let btn = UIButton()
        btn.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(btn)
        
        btn.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -20).isActive = true
        btn.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -20).isActive = true
        btn.heightAnchor.constraint(equalToConstant: 50).isActive = true
        btn.widthAnchor.constraint(equalToConstant: 50).isActive = true

Answer 2

你需要

NSLayoutConstraint.activate([
        button.bottomAnchor.constraint(equalTo: backView.bottomAnchor),
        button.rightAnchor.constraint(equalTo: backView.rightAnchor, constant: -20),
        button.heightAnchor.constraint(equalToConstant:30),
        button.widthAnchor.constraint(equalToConstant:30)
 ])

动态限制按钮在屏幕的右下角 - Swift

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