iOS UIViewController的生命周期

1.UIViewController的生命周期相关的函数如下:

override func loadView() {
super.loadView()
}
override func viewDidLoad() {
super.viewDidLoad()
}
//视图将要出现的时候执行
override func viewWillAppear(animated: Bool) {
}
//在viewWillAppear后执行，将要对子视图进行布局
override func viewWillLayoutSubviews() {
}
//已经布局完成了子视图
override func viewDidLayoutSubviews() {
}
//视图显示完成后执行
override func viewDidAppear(animated: Bool) {
}
//视图将要消失的时候执行
override func viewWillDisappear(animated: Bool) {
}
//视图已经消失的时候执行
override func viewDidDisappear(animated: Bool) {
}

override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}

2.在demo中展示相关函数的调用,代码如下:

import UIKit

class ViewController: UIViewController {
var button = UIButton()
let width = UIScreen.mainScreen().bounds.width
let height = UIScreen.mainScreen().bounds.height
let url = "http://blog.csdn.net/hnuzengchao"

override func loadView() {
super.loadView()
NSLog("loadView")
}

override func viewDidLoad() {
super.viewDidLoad()
button = UIButton(frame: CGRectMake(width/2,height/2,50,50))
button.setTitle("Click", forState: UIControlState.Normal)
button.backgroundColor = UIColor.redColor()
button.addTarget(self, action: "jump1", forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(button)
NSLog("viewDidLoad")
}

func jump1(){
let secVC = SecondViewController()
presentViewController(secVC, animated: true, completion: nil)
}

func jump2(){
UIApplication.sharedApplication().openURL(NSURL(string: "http://blog.csdn.net/hnuzengchao")!)
}
//视图将要出现的时候执行
override func viewWillAppear(animated: Bool) {
NSLog("viewWillAppear")
}
//在viewWillAppear后执行，将要对子视图进行布局
override func viewWillLayoutSubviews() {
NSLog("viewWillLayoutSubviews")
}
//已经布局完成了子视图
override func viewDidLayoutSubviews() {
NSLog("viewDidLayoutSubviews")
}
//视图显示完成后执行
override func viewDidAppear(animated: Bool) {
NSLog("viewDidAppear")
}
//视图将要消失的时候执行
override func viewWillDisappear(animated: Bool) {
NSLog("viewWillDisappear")
}
//视图已经消失的时候执行
override func viewDidDisappear(animated: Bool) {
NSLog("viewDidDisappear")
}

override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}

}

启动App之后:执行的函数如下：

2016-01-07 15:12:27.829 iOS_Life[1504:212313] loadView
2016-01-07 15:12:27.831 iOS_Life[1504:212313] viewDidLoad
2016-01-07 15:12:27.831 iOS_Life[1504:212313] viewWillAppear
2016-01-07 15:12:27.837 iOS_Life[1504:212313] viewWillLayoutSubviews
2016-01-07 15:12:27.837 iOS_Life[1504:212313] viewDidLayoutSubviews
2016-01-07 15:12:27.839 iOS_Life[1504:212313] viewWillLayoutSubviews
2016-01-07 15:12:27.839 iOS_Life[1504:212313] viewDidLayoutSubviews
2016-01-07 15:12:27.843 iOS_Life[1504:212313] viewDidAppear
点击Click按钮之后，执行的函数如下:

2016-01-07 15:13:28.184 iOS_Life[1504:212313] viewWillDisappear
2016-01-07 15:13:28.187 iOS_Life[1504:212313] viewWillLayoutSubviews
2016-01-07 15:13:28.187 iOS_Life[1504:212313] viewDidLayoutSubviews
2016-01-07 15:13:28.702 iOS_Life[1504:212313] viewDidDisappear

3.代码中写了两个action，一个action是跳到另外一个ViewController，还有一个是跳到某个网页。这两种的区别在于，跳转到另外一个ViewController是会执行viewWillDisappear等函数的，说明当前的视图消失。而跳到某个网页，没有执行viewWillDisappear等函数的，说明当前的视图并没有消失。