这就是我如何使用MDCBottomAppBarView（）。
首先创建一个底部应用栏和一个浮动按钮来访问MDCBottomAppBarView（）默认的浮动按钮。

let bottomAppBar = MDCBottomAppBarView()
var floatingButton = MDCFloatingButton()

然后，您可以配置应用栏和按钮，

override func viewDidLoad() {
    super.viewDidLoad()
    floatingButton = bottomAppBar.floatingButton
    // configure floating button and app bar
    floatingButton.setImage(UIImage(systemName: "plus"), for: UIControl.State.normal)
    floatingButton.tintColor = .white
    floatingButton.backgroundColor = UIColor(named: "customColor")
    bottomAppBar.barTintColor = UIColor(named: "customColor")
    // and important thing is you have to configure a frame for app bar
    bottomAppBar.frame = CGRect(x: 0, y: view.frame.height * 0.86, width: view.frame.width, height: view.frame.height * 0.14)
    // add the app bar in your view
    view.addSubview(bottomAppBar)
}