Question

使用Xcode ver 9.3，Swift开发iOS应用程序。

导航左栏按钮不会出现。你能告诉我如何显示左栏按钮吗？

当我尝试使用相同代码的右侧按钮时，它显示没有任何问题。

代码和故事板如下。

第一个TableView代码

import UIKit

class TableViewController: UITableViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let naviButton = UIBarButtonItem(title: "naviButton", style: UIBarButtonItemStyle.plain, target: self, action: #selector(Tapped))

        // Left bar button does not appear
        self.navigationItem.leftBarButtonItem = naviButton

        // Right bar button do appear
        self.navigationItem.rightBarButtonItem = naviButton

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
        // self.navigationItem.rightBarButtonItem = self.editButtonItem
    }

    @objc func Tapped() {
        print("Tapped")
    }

...

故事板

模拟器

Answer 1

您不能在UINavigationBar中两次放置相同的按钮。因此，创建2个单独的按钮，然后将其分配给leftbarButton和rightbarButton：

override func viewDidLoad() {
    super.viewDidLoad()

    let leftNaviButton = UIBarButtonItem(title: "lNaviButton", style: UIBarButtonItemStyle.plain, target: self, action: #selector(Tapped1))
    self.navigationItem.leftBarButtonItem = leftNaviButton

    let rightNaviButton = UIBarButtonItem(title: "rNaviButton", style: UIBarButtonItemStyle.plain, target: self, action: #selector(Tapped2))
    self.navigationItem.rightBarButtonItem = rightNaviButton
}

@objc func Tapped1() {
    print("Tapped1")
}

@objc func Tapped2() {
    print("Tapped2")
}

Answer 2

您无法将两次相同的视图添加到UI。如果您创建单个UIBarButtonItem，则可以将其添加为左侧或右侧导航项，但不能同时添加。如果你想在两边都有物品，那么只需创建另一个：

override func viewDidLoad() {
    super.viewDidLoad()

    let leftNaviButton = UIBarButtonItem(title: "naviButton", style: UIBarButtonItemStyle.plain, target: self, action: #selector(Tapped))

    // Left bar button does not appear
    self.navigationItem.leftBarButtonItem = leftNaviButton

    let rightNaviButton = UIBarButtonItem(title: "naviButton", style: UIBarButtonItemStyle.plain, target: self, action: #selector(Tapped))
    // Right bar button do appear
    self.navigationItem.rightBarButtonItem = rightNaviButton

}

Answer 3

正如我在评论中建议的那样，您的问题与您为UIBarButtonItem和self.navigationItem.rightBarButtonItem设置相同self.navigationItem.leftBarButtonItem的事实有关，您需要创建两个UIBarButtonItem并指定一个用于右边，另一个用于左边，我想你知道怎么做;）

Answer 4

您可以为UIButton创建一个扩展名，如

extension UIButton {
    class func addBarButton(tittle:String,_ target: Any, action: Selector) -> UIBarButtonItem{
        let button = UIButton(type: .system)
        button.setTitle(tittle, for: .normal)
        button.addTarget(target, action: action, for: .touchUpInside)
        return UIBarButtonItem(customView: button)
    }    
}

和你的主控制器只需要写下面的代码

  self.navigationItem.rightBarButtonItem = UIButton.addBarButton(tittle: "RNaviButton", self, action: #selector(Tapped1))
  self.navigationItem.leftBarButtonItem = UIButton.addBarButton(tittle: "LNaviButton", self, action: #selector(Tapped2))

按钮的

和动作方法

@objc func Tapped1() {
    print("Tapped1")
}
@objc func Tapped2() {
    print("Tapped2")
}

如果你想对两个按钮都采取相同的动作，你也可以在两个按钮动作中传递相同的动作。

如何显示导航左栏按钮？

4 个答案: