UIView生命周期相关函数
//构造方法,初始化时调用,不会调用init方法
- (instancetype)initWithFrame:(CGRect)frame;
//构造方法,内部会调用initWithFrame方法
- (instancetype)init;
//xib归档初始化视图后调用,如果xib中添加了子控件会在didAddSubview方法调用后调用
- (instancetype)initWithCoder:(NSCoder *)aDecoder;
//唤醒xib,可以布局子控件
- (void)awakeFromNib;
//父视图将要更改为指定的父视图,当前视图被添加到父视图时调用
- (void)willMoveToSuperview:(UIView *)newSuperview;
//父视图已更改
- (void)didMoveToSuperview;
//其窗口对象将要更改
- (void)willMoveToWindow:(UIWindow *)newWindow;
//窗口对象已经更改
- (void)didMoveToWindow;
//布局子控件
- (void)layoutSubviews;
//绘制视图
- (void)drawRect:(CGRect)rect;
//从父控件中移除
- (void)removeFromSuperview;
//销毁
- (void)dealloc;
//添加子控件时调用
- (void)didAddSubview:(UIView *)subview;
//将要移除子控件
- (void)willRemoveSubview:(UIView *)subview;
init方式创建视图,并添加到父视图中展示,不添加子控件,其生命周期调用顺序为:
[NoXibView initWithFrame:]
[NoXibView init]
[NoXibView willMoveToSuperview:]
[NoXibView didMoveToSuperview]
[NoXibView willMoveToWindow:]
[NoXibView didMoveToWindow]
[NoXibView layoutSubviews]
initWithFrame方式创建视图,并添加到父视图中展示,不添加子控件,其生命周期调用顺序为:
[NoXibView initWithFrame:]
[NoXibView willMoveToSuperview:]
[NoXibView didMoveToSuperview]
[NoXibView willMoveToWindow:]
[NoXibView didMoveToWindow]
[NoXibView layoutSubviews]
[NoXibView drawRect:]
移除销毁是调用顺序:
[NoXibView willMoveToWindow:]
[NoXibView didMoveToWindow]
[NoXibView willMoveToSuperview:]
[NoXibView didMoveToSuperview]
[NoXibView removeFromSuperview]
[NoXibView dealloc]
添加子控件展示时调用顺序:
[NoXibView initWithFrame:]
[NoXibView didAddSubview:]
[NoXibView willMoveToSuperview:]
[NoXibView didMoveToSuperview]
[NoXibView willMoveToWindow:]
[NoXibView didMoveToWindow]
[NoXibView layoutSubviews]
[NoXibView drawRect:]
添加子控件移除销毁时调用顺序:
[NoXibView willMoveToWindow:]
[NoXibView didMoveToWindow]
[NoXibView willMoveToSuperview:]
[NoXibView didMoveToSuperview]
[NoXibView removeFromSuperview]
[NoXibView dealloc]
[NoXibView willRemoveSubview:]
xib创建初始化视图, xib中不添加子控件时调用顺序:
[XibView initWithCoder:]
[XibView awakeFromNib]
[XibView willMoveToSuperview:]
[XibView didMoveToSuperview]
[XibView willMoveToWindow:]
[XibView didMoveToWindow]
[XibView layoutSubviews]
[XibView layoutSubviews]
[XibView drawRect:]
xib创建初始化视图, xib中添加子控件时调用顺序:
[XibView didAddSubview:]
[XibView initWithCoder:]
[XibView awakeFromNib]
[XibView willMoveToSuperview:]
[XibView didMoveToSuperview]
[XibView willMoveToWindow:]
[XibView didMoveToWindow]
[XibView layoutSubviews]
[XibView layoutSubviews]
[XibView drawRect:]
移除销毁时调用顺序,有子控件:
[XibView willMoveToWindow:]
[XibView didMoveToWindow]
[XibView willMoveToSuperview:]
[XibView didMoveToSuperview]
[XibView removeFromSuperview]
[NoXibView dealloc]
[NoXibView willRemoveSubview:]
UIView生命周期总结:
- init方法初始化视图,内部会调用initWithFrame方法,不会调用initWithCoder和awakeFromNib方法;
- xib归档创建视图会触发initWithCoder和awakeFromNib方法,不再调用init和initWithFrame方法;
- 添加视图调用addSubview方法会触发didAddSubview犯法.
- willMoveToSuperview和didMoveToSuperview方法,父类变化时，无论是添加到父视图还是移除父视图都会调用;在添加时willMoveToSuperview的newSuperview即为要将要添加的父视图,此时视图的superview为nil,当执行didMoveToSuperview时,视图的父视图不再为nil,为刚添加的newSuperview;移除时willMoveToSuperview的newSuperview为nil,didMoveToSuperview时,视图的父视图也为nil;
- willMoveToWindow和didMoveToWindow方法,是持有的window变化时调用,无论是添加 到窗口显示还是移除窗口消失销毁都会调用;当添加时willMoveToWindow的newWindow参数不为nil,self.window却为nil,didMoveToWindow的self.window即为newWindow;移除时willMoveToWindow的newWindow参数为nil,didMoveToWindow的self.window也为nil
- 也就是说在添加到父视图时会在willMoveToSuperview方法中将视图添加到父视图中,在willMoveToWindow添加到window中才能展示,而在移除时在willMoveToWindow将当前持有的window置nil,再在willMoveToSuperview中将父视图置nil;
UIViewController和UIView进入展示时整体生命周期调用顺序
self.view是控制器的默认视图,NoXibView是添加到self.view的子视图,UIViewController和UIView加载展示时整体生命周期调用顺序如下(红色为打印的生命周期方法,蓝色的为superview和window):
- vc(控制器)的viewDidLoad方法;
- NoXibView的willMoveToSuperview和didMoveToSuperview,此时已将NoXibView添加到父视图上;
- vc的viewWillDisappear方法,促使vc的view的superview和window还是为nil;
- NoXibView的willMoveToWindow和didMoveToWindow,此时已将NoXibView添加到widonw;
- vc的viewWillLayoutSubviews ,此时vc的view的superview和window不再为nil;
- vc的viewDidLayoutSubviews ;
- NoXibView的layoutSubviews;
- vc的viewDidAppear .
UIViewController和UIView消失销毁时整体生命周期调用顺序如下:
- vc的viewWillDisappear;
- NoXibView的willMoveToWindow,didMoveToWindow,此时NoXibView的window置nil;
- vc的viewDidDisappear;此时vc的view的window和superview都置为nil;
- vc的’dealloc’;
- NoXibView的willMoveToSuperview和didMoveToSuperview,此时NoXibView的superview置nil;
- NoXibView的removeFromSuperview;
- NoXibView的’dealloc’;
- NoXibView的’willRemoveSubview’.
总结
总而言之加载展示时:就是先将子控件添加到当前控件中,再将子控件添加到window,然后将当前控件添加到父控件中,再将当前控件添加到window中;移除销毁时:将当前空前的window置nil,再将父控件置nil,将当前控件移除销毁,再将子控件的window置nil,子控件的父控件置nil;(展示时先添加子控件再添加当前控件再添加父控件,移除时先移除父控件,再移除当前控件,再移除子控件).
开发技巧总结
- 在开发中很多方法是用不到的,所以也没必要都记顺序,上面之所以要打印superview和window,是因为不管是autoresize还是autolayout布局都是基于父视图的,wiondw是最终的显示载体;
- 对于UIViewController,viewDidLoad:方法是视图加载完成,我们可以在里面添加子视图,设置相关属性和布局等,所有和self.view相关的操作在该方法中添加比较合适;viewWillAppear:视图即将显示时调用;viewWillLayoutSubviews:视图将要布局其子视图时被调用;viewDidLayoutSubviews:视图布局完成其子视图时被调用;viewDidAppear视图显示后被调用;viewWillDisappear:视图将要消失时调用;viewDidDisappear:视图已经消失时调用;
- 注意:viewWillAppear:和viewWillDisappear:有时要成对使用;viewDidAppear和viewDidDisappear:有时要成对使用,比如显示该页面定位,消失时结束定位;还比如该页面显示时影藏导航,去其他页面时恢复导航;
UIView的layoutSubviews会被经常调用,下面说下layoutsubview的调用情况：
1 addSubview会触发layoutSubviews，如果addSubview 如果连续2个 只会执行一次，具体原因下面说。
2 设置view的Frame会触发layoutSubviews，必须是frame的值设置前后发生了变化。
3 滚动一个UIScrollView会触发layoutSubviews。
4 旋转Screen会触发父UIView上的layoutSubviews事件。
5 、改变一个UIView大小的时候也会触发父UIView上的layoutSubviews事件。