1. 增加了類型為 UINavigationItem.ItemStyle 的屬性style用于描述 UINavigationItem 在 UINavigationBar 上的布局，共有 3 種樣式：navigator（默認(rèn)樣式），browser（瀏覽器樣式）與editor（編輯器樣式）。

//  Created by YungFan
import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .red
        // 左側(cè)
        navigationItem.leftBarButtonItems = [
            UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(gotoNextViewController)),
            UIBarButtonItem(barButtonSystemItem: .bookmarks, target: nil, action: nil)]
        // 標(biāo)題
        navigationItem.title = "導(dǎo)航欄"
        // navigationItem.titleView = UISwitch()
        // 中間
        let fixedGroup = UIBarButtonItemGroup.fixedGroup(items: [
            UIBarButtonItem(title: "撤銷", image: UIImage(systemName: "arrow.uturn.backward"),
                            primaryAction: UIAction { _ in
                            }),
            UIBarButtonItem(title: "反撤銷", image: UIImage(systemName: "arrow.uturn.forward"),
                            primaryAction: UIAction { _ in
                            })])
        let movableGroup = UIBarButtonItem(title: "裁剪", image: UIImage(systemName: "crop"),
                                           primaryAction: UIAction { _ in
                                           }).creatingMovableGroup(customizationIdentifier: "Cropping")
        navigationItem.centerItemGroups = [fixedGroup, movableGroup]
        // 右側(cè)
        navigationItem.rightBarButtonItems = [
            UIBarButtonItem(barButtonSystemItem: .camera, target: nil, action: nil),
            UIBarButtonItem(barButtonSystemItem: .done, target: nil, action: nil)]
        // 設(shè)置style
        navigationItem.style = .editor
    }

    // MARK: 導(dǎo)航跳轉(zhuǎn)
    @objc func gotoNextViewController(_ sender: UIBarButtonItem) {
        let nextViewController = UIViewController()
        nextViewController.view.backgroundColor = .red
        nextViewController.navigationItem.title = "下一頁(yè)"

        navigationController?.pushViewController(nextViewController, animated: true)
    }
}

2. 增加了閉包類型的屬性titleMenuProvider用于給當(dāng)前導(dǎo)航欄的標(biāo)題增加操作菜單。

//  Created by YungFan
import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        navigationItem.title = "標(biāo)題"
        // 設(shè)置titleMenuProvider
        navigationItem.titleMenuProvider = { _ in
            let favorite = UIAction(title: "Favorite", image: UIImage(systemName: "heart.fill")) { _ in
                print("favorite")
            }
            let share = UIAction(title: "Share", image: UIImage(systemName: "square.and.arrow.up.fill")) { _ in
                print("share")
            }
            let delete = UIAction(title: "Delete",
                                  image: UIImage(systemName: "trash.fill"),
                                  attributes: [.destructive]) { _ in
                print("delete")
            }
            return UIMenu(children: [favorite, share, delete])
        }
    }
}

3. 增加了類型為 UIAction 的屬性backAction用于實(shí)現(xiàn)返回按鈕的點(diǎn)擊事件。

//  Created by YungFan
import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        // 設(shè)置backAction
        navigationItem.backAction = UIAction(handler: { _ in
            print("返回按鈕點(diǎn)擊事件")
        })
    }
}