请尝试将以下代码放入viewDidLoad：

let height: CGFloat = 75
let navbar = UINavigationBar(frame: CGRect(x: 0, y: 0, width: UIScreen.mainScreen().bounds.width, height: height))
navbar.backgroundColor = UIColor.whiteColor()
navbar.delegate = self

let navItem = UINavigationItem()
navItem.title = "Title"
navItem.leftBarButtonItem = UIBarButtonItem(title: "Left Button", style: .Plain, target: self, action: nil)
navItem.rightBarButtonItem = UIBarButtonItem(title: "Right Button", style: .Plain, target: self, action: nil)

navbar.items = [navItem]

view.addSubview(navbar)

collectionView?.frame = CGRect(x: 0, y: height, width: UIScreen.mainScreen().bounds.width, height: (UIScreen.mainScreen().bounds.height - height))

当然，height可以是你想要的任何东西，而UIBarButton的动作是你想要的任何功能的选择器（你也根本不需要按钮）。

编辑：

1.已调整collectionView的框架，使其不会与UINavigationBar重叠。
1.将高度设为常数，以便可以在一个位置变更其所有指涉。

Swift 4的更新答案：

private func addNavigationBar() {
    let height: CGFloat = 75
    var statusBarHeight: CGFloat = 0
    if #available(iOS 13.0, *) {
        statusBarHeight = view.window?.windowScene?.statusBarManager?.statusBarFrame.height ?? 0
    } else {
        statusBarHeight = UIApplication.shared.statusBarFrame.height
    }
    let navbar = UINavigationBar(frame: CGRect(x: 0, y: statusBarHeight, width: UIScreen.main.bounds.width, height: height))
    navbar.backgroundColor = UIColor.white
    navbar.delegate = self as? UINavigationBarDelegate

    let navItem = UINavigationItem()
    navItem.title = "Sensor Data"
    navItem.leftBarButtonItem = UIBarButtonItem(title: "Back", style: .plain, target: self, action: #selector(dismissViewController))

    navbar.items = [navItem]

    view.addSubview(navbar)

    self.view?.frame = CGRect(x: 0, y: height, width: UIScreen.main.bounds.width, height: (UIScreen.main.bounds.height - height))
}

这是swift 5的版本。

class ViewController: UIViewController, UINavigationBarDelegate {

override func viewDidLoad() {
    super.viewDidLoad()

    view.addSubview(toolbar)
    toolbar.delegate = self

    let height: CGFloat = 75
    let navbar = UINavigationBar(frame: CGRect(x: 20, y: 20, width: UIScreen.main.bounds.width, height: height))
    navbar.backgroundColor = UIColor.white
    navbar.delegate = self

    let navItem = UINavigationItem()
    navItem.title = "Title"
    navItem.leftBarButtonItem = UIBarButtonItem(title: "Left Button", style: .plain, target: self, action: nil)
    navItem.rightBarButtonItem = UIBarButtonItem(title: "Right Button", style: .plain, target: self, action: nil)

    navbar.items = [navItem]

    view.addSubview(navbar)

    self.view.frame = CGRect(x: 0, y: height, width: UIScreen.main.bounds.width, height: (UIScreen.main.bounds.height - height))

}

}