无法以编程方式添加条形按钮项答案

【问题标题】：Unable to Add Bar Button Item Programatically无法以编程方式添加条形按钮项
【发布时间】：2017-04-03 17:49:01
【问题描述】：

func myPlaceViewMoreWasPressed() {
    print("myPlaceViewMore was pressed")

    let vc = MyPlacesViewController(nil)
    let nav = UINavigationController(rootViewController: vc)
    let dismissButton = UIBarButtonItem.init(title: "Dismiss", style: .plain, target: self, action: #selector(dismissButtonWasPressed))
    nav.navigationItem.leftBarButtonItem = dismissButton

    self.present(nav, animated: true, completion: nil)
}

应该很简单...实例化一个 ViewController，将其包含在导航控制器中，初始化一个 UIBarButtonItem 并将其设置为导航的 leftBarButtonItem。我也试过这样：

func myPlaceViewMoreWasPressed() {
    print("myPlaceViewMore was pressed")

    let vc = MyPlacesViewController(nil)
    let nav = UINavigationController(rootViewController: vc)
    let dismissButton = UIBarButtonItem.init(title: "Dismiss", style: .plain, target: self, action: #selector(dismissButtonWasPressed))
    nav.navigationItem.setLeftBarButton(dismissButton, animated: true)

    self.present(nav, animated: true, completion: nil)
}

但是按钮不会出现。

【问题讨论】：

标签： ios swift cocoa-touch uinavigationbar

【解决方案1】：

您需要更新视图控制器的navigationItem，而不是导航控制器。在将视图控制器设置为根控制器之前，我会这样做。

func myPlaceViewMoreWasPressed() {
    print("myPlaceViewMore was pressed")

    let vc = MyPlacesViewController(nil)
    let dismissButton = UIBarButtonItem.init(title: "Dismiss", style: .plain, target: self, action: #selector(dismissButtonWasPressed))
    vc.navigationItem.leftBarButtonItem = dismissButton

    let nav = UINavigationController(rootViewController: vc)

    self.present(nav, animated: true, completion: nil)
}

【讨论】：