iOS ViewController生命周期最佳实践

Question

有没有人知道一个很好的教程,深入解释了视图控制器的生命周期.我已经阅读了文档,所以请不要将我与他们联系起来.我只是在寻找每个函数的实际解释,例如viewDidLoad和viewWillAppear,viewWillLayoutSubviews等,以及何时最好将它们与Swift中的示例一起使用.如果没有教程,任何人都愿意在答案中解释它们.

Answer 1

我使用swift为你显示代码.

import UIKit

class LifeCycleViewController: UIViewController {
    // MARK: -property
    lazy var testBtn: UIButton! = {
        var btn: UIButton = UIButton()
        btn.backgroundColor = UIColor.redColor()
        return btn
    }()

    // MARK: -life cycle
    override func viewDidLoad() {
        super.viewDidLoad()
        println("View has loaded")
        // set the superView backgroudColor
        self.view.backgroundColor = UIColor.blueColor()
        // add testBtn to the superView
        self.view.addSubview(self.testBtn)
    }
    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        println("View will appear")
    }
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        println("View has appeared")
    }
    override func viewWillDisappear(animated: Bool) {
        super.viewWillDisappear(animated)
        println("View will disappear")
    }
    override func viewDidDisappear(animated: Bool) {
        super.viewDidDisappear(animated)
        println("View has desappeared")
    }
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        println("SubViews will layout")
        // layout subViews 
        self.testBtn.frame = CGRectMake(100, 100, 100, 100)
    }
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        println("SubViews has layouted")
        var testBtn_Width = self.testBtn.frame.width
        println("testBtn's width is \(testBtn_Width)")
    }


}

结果如下:

View has loaded
View will appear
SubViews will layout
SubViews has layouted
testBtn's width is 100.0
SubViews will layout
SubViews has layouted
testBtn's width is 100.0
View has appeared

您可以清楚地看到ViewController的生命周期.

Answer 2

这张图片上的例子也不错.