iOS ViewController生命周期

iOS 显示是 约束 -> 布局 -> 显示的过程，有时候你操作改变frame没有反应是因为还没有确定frame

TestCode

---

代码语言：javascript复制

//
//  ViewController.swift
//  TestXib
//
//  Created by zhangyu on 2019/11/13.
//  Copyright © 2019 zy. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    override func loadView() {
        super.loadView()
        print("loadView")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        print("viewDidLoad")
    }
    
    override func viewWillAppear(_ animated: Bool) {
       super.viewWillAppear(animated)
       print("viewWillAppear")
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        print("viewDidAppear")
    }
    
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        print("viewWillLayoutSubviews")
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        print("viewDidLayoutSubviews")
    }
    
    override func updateViewConstraints() {
        super.updateViewConstraints()
        print("updateViewConstraints")
    }

}

打印结果

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代码语言：javascript复制

loadView
viewDidLoad
viewWillAppear
updateViewConstraints
viewWillLayoutSubviews
viewDidLayoutSubviews
viewDidAppear

分析

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直接修改Frame

viewDidAppear 才能确定布局，需要在这个方法直接修改frame。

如果不想在显示之后修改，需要修改约束，然后Layout，显示。

ios frame layout ode 布局

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