动态限制按钮位于屏幕的右下角 - Swift答案

【问题标题】：Dynamically restrict button to be in the lower right corner of the screen - Swift动态限制按钮位于屏幕的右下角 - Swift
【发布时间】：2020-11-05 18:22:13
【问题描述】：

如何从背景视图中动态限制下方的按钮，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吗？

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)

【问题讨论】：

标签： swift storyboard constraints xib

【解决方案1】：

这是视图右下方添加按钮的代码

        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

【讨论】：

【解决方案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)
 ])

【讨论】：