一般做圖類的APP對於控制元件圖層順序，疊放順序有一定的要求，下面是常用的幾個方法彙總：

- (void)removeFromSuperview;

- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index;

- (void)exchangeSubviewAtIndex:(NSInteger)index1 withSubviewAtIndex:(NSInteger)index2;

- (void)addSubview:(UIView *)view;

- (void)insertSubview:(UIView *)view belowSubview:(

- (void)insertSubview:(UIView *)view aboveSubview:(UIView *)siblingSubview;

- (void)bringSubviewToFront:(UIView *)view;

- (void)sendSubviewToBack:(UIView *)view;

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

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

- (void)willMoveToSuperview:(

- (void)didMoveToSuperview;

- (void)willMoveToWindow:(nullableUIWindow *)newWindow;

- (void)didMoveToWindow;