uikit——UIView——event

event

- (void)didAddSubview:(UIView *)subview;
- (void)willRemoveSubview:(UIView *)subview;

- (void)willMoveToSuperview:(nullable UIView *)newSuperview;
- (void)didMoveToSuperview;
- (void)willMoveToWindow:(nullable UIWindow *)newWindow;
- (void)didMoveToWindow;

解释：

• 默认这些方法什么都不做，可override自定义
• newSuperview可为nil，只要view.superview变化即可
• newWindow可为nil，只要view.window变化即可