ios - 如何在应用程序退出时保存 UISwitch 状态 (Swift)

Question

如何保存多个开关的状态，以便当应用程序退出并重新打开时，所有开关都不会处于退出前的相同状态。这是我为快速作业管理器编写的非常简单的代码。

//
//  ViewController.swift
//  HomeworkManager
//
//  Created by Nate Parker on 9/2/14.
//  Copyright (c) 2014 Nathan Parker. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


@IBAction func resetClicked(sender: AnyObject) {
    spanish.setOn(false, animated: true);
    algebra.setOn(false, animated: true);
    amerCult.setOn(false, animated: true);
    bio.setOn(false, animated: true);
    col.setOn(false, animated: true);
}

@IBOutlet var spanish: UISwitch
@IBOutlet var algebra: UISwitch
@IBOutlet var amerCult: UISwitch
@IBOutlet var bio: UISwitch
@IBOutlet var col: UISwitch


}

Answer 1

在 AppDelegate 类中，在 applicationDidEnterBackground 中发布通知，这样当应用程序进入后台时，您的 View Controller 将能够收到通知:

func applicationDidEnterBackground(application: UIApplication!) {
    NSNotificationCenter.defaultCenter().postNotificationName("kSaveSwitchesStatesNotification", object: nil);   
}

在您的 View Controller 类中添加此代码:

override func viewDidLoad() {
    super.viewDidLoad()
    self.restoreSwitchesStates();

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "saveSwitchesStates", name: "kSaveSwitchesStatesNotification", object: nil);
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func saveSwitchesStates() {
    NSUserDefaults.standardUserDefaults().setBool(spanish!.on, forKey: "spanish");
    NSUserDefaults.standardUserDefaults().setBool(algebra!.on, forKey: "algebra");
    NSUserDefaults.standardUserDefaults().setBool(amerCult!.on, forKey: "amerCult");
    NSUserDefaults.standardUserDefaults().setBool(bio!.on, forKey: "bio");
    NSUserDefaults.standardUserDefaults().setBool(col!.on, forKey: "col");

    NSUserDefaults.standardUserDefaults().synchronize();
}

func restoreSwitchesStates() {
    spanish!.on = NSUserDefaults.standardUserDefaults().boolForKey("spanish");
    algebra!.on = NSUserDefaults.standardUserDefaults().boolForKey("algebra");
    amerCult!.on = NSUserDefaults.standardUserDefaults().boolForKey("amerCult");
    bio!.on = NSUserDefaults.standardUserDefaults().boolForKey("bio");
    col!.on = NSUserDefaults.standardUserDefaults().boolForKey("col");
}

首先，添加 viewcontroller 作为应用程序进入后台时发布的通知的观察者。当触发此通知时，它将调用 saveSwitchesStates() 方法，该方法将开关状态保存在 NSUserDefaults 中。同样在 viewDidLoad() 中调用 restoreSwitchesStates()，它将从 NSUserDefaults

中读取开关状态的存储 bool 值