ios - 如何显示导航左栏按钮？

Question

使用 Xcode 9.3 版 Swift 开发 iOS 应用程序。

导航左栏按钮不出现。你能告诉我如何显示左栏按钮吗？

当我用相同的代码尝试右侧的按钮时，它显示没有任何问题。

代码和 Storyboard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")
    }

...

Storyboard

模拟器

Answer 1

You can not place same button twice in UINavigationBar. So create 2 separate button and then assign them to leftbarButton and 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")
}