Question

我想像这样从第一个视图重新启动应用程序：

func applicationWillEnterForeground(_ application: UIApplication) {
    let storyBoard: UIStoryboard = UIStoryboard(name: "SplashScreen", bundle: nil)
    let splashScreen = storyBoard.instantiateViewController(withIdentifier: "splashVC") as! SplashScreenController
    self.window?.addSubview(splashScreen.view)

}

但是当应用再次被唤醒时。我的代表返回零。为什么？

SplashScreenVM.swift：

  import Foundation
protocol SplashScreenVMProtocol: class {
    func fetchDataSuccessfuly()
    func failedFetchData()
}
class SplashScreenVM {

    weak var delegate: SplashScreenVMProtocol!
    private let dataManager = DataManagement()
    private let coreDataManager = CoreDataManagement()

    lazy var itemsCount = coreDataManager.getRecords("Categories").count
    lazy var timestamp = coreDataManager.getRecords("Timestamp")

    init(){}

    func setUpData() {
        dataManager.fetchData(timestamp: 0 ) { (err, res) in
        //dataManager.fetchData(timestamp: timestamp.count == 0 ? 0 : timestamp[0].value(forKey: "time") as! Int64) { (err, res) in
            //print("categories count: \(self.coreDataManager.getRecords("Categories").count) and artciles count \(self.coreDataManager.getRecords("Articles").count)")

            if(err != nil) {
                print("Error: \(String(describing: err))");
                self.delegate.failedFetchData()
                return
            }
                self.coreDataManager.setTimestamp()
                self.delegate.fetchDataSuccessfuly()
        }
    }
}

打开应用程序时的第一个视图SplashScreenController：

    import UIKit
import Alamofire

class SplashScreenController: UIViewController, SplashScreenVMProtocol {

    @IBOutlet weak var loadSpinner: UIActivityIndicatorView!

    let splashScreenVM = SplashScreenVM()

    let storyBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    lazy var MainController = storyBoard.instantiateViewController(withIdentifier: "MainVC")

    override func viewDidLoad() {
        super.viewDidLoad()


        splashScreenVM.delegate = self  //Looks like something wrong with this
        print("apapapaap \(splashScreenVM.delegate)")
        loadSpinner.hidesWhenStopped = true
        loadSpinner.startAnimating()

        switch Reachability.isConnectedToNetwork() {
            case true:
                splashScreenVM.setUpData()
            case false:
                self.loadSpinner.stopAnimating()
                splashScreenVM.itemsCount == 0 ? print("butinai reikia intiko") : print("keliaujam i pagr.meniu")
        }
    }

    func fetchDataSuccessfuly() {
        self.loadSpinner.stopAnimating()
        self.present(MainController, animated: true, completion: nil)
    }

    func failedFetchData() {
        self.loadSpinner.stopAnimating()
        if(splashScreenVM.itemsCount != 0) {
            self.present(MainController, animated: true, completion: nil)
        }
        return
    }   
}

我做错了什么？我的弱变量代表：SplashScreenVMProtocol！返回nil。当应用再次苏醒时，是从头开始启动应用的更好方法吗？

Answer 1

您没有在applicationWillEnterForeground中保留您的splashScreen变量。您将splashScreen视图设置为子视图，但是splashScreen本身只是一个局部变量。当它超出范围时，对象将被释放。

您的数据访问正在异步进行，因此当它完成时，原始的splashScreen对象已经被释放并且不再存在。

有些东西需要保留在splashScreen上。

Answer 2

好了，我解决了这个问题，也许...刚从weak var delegate: SplashScreenVMProtocol!更改为var delegate: SplashScreenVMProtocol!，并且效果很好，但是在控制台中却得到了这样的提示：“建议不要在分离的视图控制器上呈现视图控制器”

在调用applicationWillEnterForeground之后重新启动应用程序

2 个答案: