swift - Self.revealViewController() 返回 nil

Question

我目前正在尝试使用平移手势来显示 Controller 。截至目前，我的打开按钮可以使用，但是当我添加最后一行时，我的程序崩溃了，因为 revealViewController 为 nil。 pods 链接:https://github.com/John-Lluch/SWRevealViewController .

    import Foundation
    import UIKit
    class MainViewController : UIViewController{
    @IBOutlet weak var mainButton: UIView!
    @IBOutlet weak var Open: UIBarButtonItem!
    override func viewDidLoad() {
        super.viewDidLoad()

    }
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated);
        mainButton.makeCircle();
        Open.target = self.revealViewController()
        Open.action = #selector(SWRevealViewController.revealToggle(_:));
        self.view.addGestureRecognizer(self.revealViewController().panGestureRecognizer());
    }
}

Answer 1

您可能还没有将 SWRevealViewController 设置为 rootViewController。请记住在您的Identity inspector 中将Custom Class 和Storyboard ID 设置为SWRevealViewController。

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let rootVC = storyboard.instantiateViewController(withIdentifier: "SWRevealViewController")    
    self.view.window?.rootViewController = rootVC

    // Cont. with your code...
}

---

如果您需要在开始时显示登录页面，您需要在 AppDelegate 中添加一个函数，它允许窗口更新 rootViewController

func changeRootVCToSWRevealVC () {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let rootVC = storyboard.instantiateViewController(withIdentifier: "SWRevealViewController")
    if let window = self.window{
        window.rootViewController = rootVC
    }
}

用户登录后，您可以将rooViewController更改为SWRevealViewController。

if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
    appDelegate.changeRootVCToSWRevealVC()
}

如果您有一个存储上次登录状态的变量，并且想直接导航到抽屉导航菜单而不是 LoginViewController。

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

    let rootVCId = isLoggedin ? "SWRevealViewController" : "LoginViewController"
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let rootVC = storyboard.instantiateViewController(withIdentifier: rootVCId)    
    self.view.window?.rootViewController = rootVC

    // Cont. with your code...
}