以编程方式快速设置 LoginButton 的约束

Question

我想将 Facebook 身份验证的登录按钮设置到 View 底部。我尝试了这个，但它不起作用:

let lb = LoginButton(readPermissions: [ .email, .publicProfile ])
    lb.center = view.bottomAnchor

不知道如何将其水平设置到 View 中心底部

Answer 1

 let lb = UIButton()//LoginButton(readPermissions: [ .email, .publicProfile ])
        lb.center = self.view.center

//设置约束

  NSLayoutConstraint.activate([
        lb.centerXAnchor.constraint(equalTo: self.view.centerXAnchor), // centerXAnchor which set over the view center
        lb.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 70.0), // BottomAnchor to set with botton target
        lb.widthAnchor.constraint(equalToConstant: 170.0), // Width Anchor to set appropriate width
        lb.heightAnchor.constraint(equalToConstant: 44.0) // Height Anchor to set appropriate hegiht of the button.
        ])

self.view.addSubview(lb)
lb.delegate = self

如果编程约束有任何问题，您甚至可以从 UI 界面(Storyboard 或 XIB)添加该按钮。

简单地，使用@IBOutlet 创建一个实例。分配 FBSDKLoginButton 类并将委托(delegate)设置为该按钮。

@IBOutlet weak var loginButton: FBSDKLoginButton!

欲了解更多信息，请访问此链接:Facebook Login button for Swift