iOS：捋一遍View的生命周期

一、介绍

前面介绍了VC的生命周期，闲着没事也来捋一捋View的生命周期，简单用两个类型的View来监测。一个View纯代码创建，另一个View使用Xib创建。

二 、代码

MyCodeView: 

//
//  MyCodeView.m
//  生命周期
//
//  Created by 夏远全 on 2019/11/3.
//  Copyright © 2019 Beijing Huayue Education Technology Co., Ltd. All rights reserved.
//

#import "MyCodeView.h"

@implementation MyCodeView

- (instancetype)initWithFrame:(CGRect)frame  {
    NSLog(@"myCodeView-------%s",__func__);
    return [super initWithFrame:frame];
}

- (nullable instancetype)initWithCoder:(NSCoder *)coder {
    NSLog(@"myCodeView-------%s",__func__);
    return [super initWithCoder:coder];
}

-(void)awakeFromNib {
    NSLog(@"myCodeView-------%s",__func__);
    return [super awakeFromNib];
}

-(instancetype)init {
    NSLog(@"myCodeView-------%s",__func__);
    return [super init];
}

- (void)willMoveToSuperview:(nullable UIView *)newSuperview {
    NSLog(@"myCodeView-------%s",__func__);
    [super willMoveToSuperview:newSuperview];
}

- (void)didMoveToSuperview {
    NSLog(@"myCodeView-------%s",__func__);
    [super didMoveToSuperview];
}

- (void)willMoveToWindow:(nullable UIWindow *)newWindow {
    NSLog(@"myCodeView-------%s",__func__);
    [super willMoveToWindow:newWindow];
}

- (void)didMoveToWindow {
    NSLog(@"myCodeView-------%s",__func__);
    [super didMoveToWindow];
}

- (void)layoutSubviews {
    NSLog(@"myCodeView-------%s",__func__);
    [super layoutSubviews];
}

- (void)drawRect:(CGRect)rect {
    NSLog(@"myCodeView-------%s",__func__);
    [super drawRect:rect];
}

-(void)dealloc {
    NSLog(@"myCodeView-------%s",__func__);
}

@end

MyXibView: 

//
//  MyXibView.m
//  生命周期
//
//  Created by 夏远全 on 2019/11/3.
//

#import "MyXibView.h"

@implementation MyXibView

- (instancetype)initWithFrame:(CGRect)frame  {
    NSLog(@"myXibView-------%s",__func__);
    return [super initWithFrame:frame];
}

- (nullable instancetype)initWithCoder:(NSCoder *)coder {
    NSLog(@"myXibView-------%s",__func__);
    return [super initWithCoder:coder];
}

-(void)awakeFromNib {
    NSLog(@"myXibView-------%s",__func__);
    return [super awakeFromNib];
}

-(instancetype)init {
    NSLog(@"myXibView-------%s",__func__);
    return [super init];
}

- (void)willMoveToSuperview:(nullable UIView *)newSuperview {
    NSLog(@"myXibView-------%s",__func__);
    [super willMoveToSuperview:newSuperview];
}

- (void)didMoveToSuperview {
    NSLog(@"myXibView-------%s",__func__);
    [super didMoveToSuperview];
}

- (void)willMoveToWindow:(nullable UIWindow *)newWindow {
    NSLog(@"myXibView-------%s",__func__);
    [super willMoveToWindow:newWindow];
}

- (void)didMoveToWindow {
    NSLog(@"myXibView-------%s",__func__);
    [super didMoveToWindow];
}

- (void)layoutSubviews {
    NSLog(@"myXibView-------%s",__func__);
    [super layoutSubviews];
}

- (void)drawRect:(CGRect)rect {
    NSLog(@"myXibView-------%s",__func__);
    [super drawRect:rect];
}

-(void)dealloc {
    NSLog(@"myCodeView-------%s",__func__);
}

@end

三 、注释

 init: 通过init实例化时调用，最终会调用initWithFrame，默认使用frame为CGRectZero

 initWithFrame: 给出一个frame进行实例化时，会调用

 initWithCoder: 通过xib文件创建时，进行反序列化调用

 awakeFromNib: 通过xib反序列化后唤醒，初始化调用

 willMoveToSuperview: 在视图即将加入或者移除时调用，如果参数newSuperview有值，则为即将加入到父视图，如果为空值，则即将从父视图移除

 didMoveToSuperview: 在视图即完全加入或者移除时调用，如果参数newSuperview有值，则为完全加入到父视图，如果为空值，则完全从父视图移除

 willMoveToWindow: 在视图即将加入或者移除时调用，如果参数newWindow有值，则为即将加入到窗体，如果为空值，则即将从窗体移除

 didMoveToWindow: 在视图完全加入或者移除时调用，如果参数newWindow有值，则为完全加入到窗体，如果为空值，则完全从窗体移除

 layoutSubviews: 对所有的子视图进行布局时调用

 drawRect: 通过xib文件创建的view在结束布局后进行绘制，此时调用

 dealloc: 当前视图从父视图移除并置为空时，对象销毁调用

四 、测试

MyCodeView：

- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"创建过程：");
    _codeView = [[MyCodeView alloc] init];
   [self.view addSubview:_codeView];
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"移除过程：");
    [self.codeView removeFromSuperview];
    [self setCodeView:nil];
}

2019-11-03 18:53:48.017455+0800 生命周期[7776:582010] 创建过程：
2019-11-03 18:53:48.017693+0800 生命周期[7776:582010] myCodeView--------[MyCodeView init]
2019-11-03 18:53:48.017831+0800 生命周期[7776:582010] myCodeView--------[MyCodeView initWithFrame:]
2019-11-03 18:53:48.018089+0800 生命周期[7776:582010] myCodeView--------[MyCodeView willMoveToSuperview:]
2019-11-03 18:53:48.018259+0800 生命周期[7776:582010] myCodeView--------[MyCodeView didMoveToSuperview]
2019-11-03 18:53:48.030801+0800 生命周期[7776:582010] myCodeView--------[MyCodeView willMoveToWindow:]
2019-11-03 18:53:48.031085+0800 生命周期[7776:582010] myCodeView--------[MyCodeView didMoveToWindow]
2019-11-03 18:53:48.035874+0800 生命周期[7776:582010] myCodeView--------[MyCodeView layoutSubviews]
2019-11-03 18:53:49.043080+0800 生命周期[7776:582010] 移除过程：
2019-11-03 18:53:49.043505+0800 生命周期[7776:582010] myCodeView--------[MyCodeView willMoveToSuperview:]
2019-11-03 18:53:49.043670+0800 生命周期[7776:582010] myCodeView--------[MyCodeView willMoveToWindow:]
2019-11-03 18:53:49.043856+0800 生命周期[7776:582010] myCodeView--------[MyCodeView didMoveToWindow]
2019-11-03 18:53:49.043977+0800 生命周期[7776:582010] myCodeView--------[MyCodeView didMoveToSuperview]
2019-11-03 18:53:49.044246+0800 生命周期[7776:582010] myCodeView--------[MyCodeView dealloc]

MyXibView：

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSLog(@"创建过程："); 
    _xibView = [[NSBundle mainBundle] loadNibNamed:@"MyXibView" owner:self options:nil][0];
    [self.view addSubview:_xibView];
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"移除过程：");
    [self.xibView removeFromSuperview];
    [self setXibView:nil];
}

2019-11-03 18:54:37.271733+0800 生命周期[7807:583483] 创建过程：
2019-11-03 18:54:37.272366+0800 生命周期[7807:583483] myXibView--------[MyXibView initWithCoder:]
2019-11-03 18:54:37.272802+0800 生命周期[7807:583483] myXibView--------[MyXibView awakeFromNib]
2019-11-03 18:54:37.273005+0800 生命周期[7807:583483] myXibView--------[MyXibView willMoveToSuperview:]
2019-11-03 18:54:37.273185+0800 生命周期[7807:583483] myXibView--------[MyXibView didMoveToSuperview]
2019-11-03 18:54:37.285532+0800 生命周期[7807:583483] myXibView--------[MyXibView willMoveToWindow:]
2019-11-03 18:54:37.285846+0800 生命周期[7807:583483] myXibView--------[MyXibView didMoveToWindow]
2019-11-03 18:54:37.291993+0800 生命周期[7807:583483] myXibView--------[MyXibView layoutSubviews]
2019-11-03 18:54:37.292182+0800 生命周期[7807:583483] myXibView--------[MyXibView layoutSubviews]
2019-11-03 18:54:37.292659+0800 生命周期[7807:583483] myXibView--------[MyXibView drawRect:]
2019-11-03 18:54:38.979328+0800 生命周期[7807:583483] 移除过程：
2019-11-03 18:54:38.979581+0800 生命周期[7807:583483] myXibView--------[MyXibView willMoveToSuperview:]
2019-11-03 18:54:38.979720+0800 生命周期[7807:583483] myXibView--------[MyXibView willMoveToWindow:]
2019-11-03 18:54:38.979915+0800 生命周期[7807:583483] myXibView--------[MyXibView didMoveToWindow]
2019-11-03 18:54:38.980028+0800 生命周期[7807:583483] myXibView--------[MyXibView didMoveToSuperview]
2019-11-03 18:54:38.980257+0800 生命周期[7807:583483] myCodeView--------[MyXibView dealloc]

五 、总结

• 不论是纯代码的创建View还是xib创建的View，在添加到容器中和从容器中移除时，都会调用willMoveToSuperview、didMoveToSuperview、willMoveToWindow、didMoveToWindow这四个方法，只不过调用顺序有所变化；
• 使用纯代码创建View时，只要调用了init方法，就一定会调用initWithFrame方法，会调用一次布局；
• 使用Xib创建的View时，需要进行反序列化和唤醒，也即调用initWithCoder、awakeFromNib方法, 会调用两次布局，然后进行绘制；