在UISplitView顶部(浮动)添加一个按钮- Swift

// CustomViewController.swift

import UIKit

class CustomViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建按钮
        let button = UIButton(type: .system)
        button.setTitle("按钮", for: .normal)
        button.addTarget(self, action: #selector(buttonTapped), for: .touchUpInside)
        
        // 设置按钮位置和大小
        button.frame = CGRect(x: 0, y: 0, width: 100, height: 40)
        
        // 将按钮添加到导航栏
        navigationItem.leftBarButtonItem = UIBarButtonItem(customView: button)
    }
    
    @objc func buttonTapped() {
        // 按钮点击事件处理逻辑
    }
}

// MasterViewController.swift

import UIKit

class MasterViewController: UITableViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建CustomViewController实例
        let customViewController = CustomViewController()
        
        // 将CustomViewController添加为子视图控制器
        addChild(customViewController)
        
        // 将CustomViewController的视图添加到导航栏
        navigationItem.leftBarButtonItem = UIBarButtonItem(customView: customViewController.view)
        
        // 完成添加
        customViewController.didMove(toParent: self)
    }
}