Swift - func viewWillAppear

Question

我有一个标准的SingleViewApplication项目。

ViewController.swift

import UIKit
class ViewController: UIViewController {

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

启动应用程序时，将调用viewDidLoad。

我的场景：

• 按主页按钮(applicationDidEnterBackground)
• 召回应用程序(applicationWillEnterForeground) viewDidLoad也没有被调用。

还有别的功能可以覆盖吗？

Answer 1

如果您想快速调用viewWillAppear，请使用此命令。

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated) // No need for semicolon
}

Answer 2

最佳实践是在您的UIApplicationWillEnterForegroundNotification和UIApplicationWillEnterBackgroundNotification中注册ViewController

public override func viewDidLoad()
{
    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "applicationWillEnterForeground:", name: UIApplicationWillEnterForegroundNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "applicationWillEnterBackground:", name: UIApplicationDidEnterBackgroundNotification, object: nil)
}

deinit {
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

func applicationWillEnterForeground(notification: NSNotification) {
    println("did enter foreground")
}

func applicationWillEnterBackground(notification: NSNotification) {
    println("did enter background")
}

Answer 3

根据诺亚的答复：

在ViewController.swift上添加刷新函数并从AppDelegate.swift > applicationWillEnterForeground调用它

ViewController.swift  

import UIKit

class ViewController: UIViewController {

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

    func refresh(){
        println("refresh");
    }
}

。

AppDelegate.swift
func applicationWillEnterForeground(application: UIApplication!) {
    // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
    ViewController().refresh();
}

输出：

viewDidLoad  
refresh  
refresh  
refresh  
refresh