Objective-C / Cocoa Touch 类，用于管理一个垂直的 "堆叠" UIView 和 UIViewController。这相对于向应用程序中添加额外的 UIWindows 或无组织地添加子视图到主 UIWindow 是一个有用的替代方案。可以指定视图的 Z 位置，让您排列哪些视图在另一些视图前面。
DRWindowController *windowController = [[DRWindowController alloc] initWithNibName:nil bundle:nil];
self.window.rootViewController = windowController;
[self.window makeKeyAndVisible];
// Add root controller to window manager
UIViewController *mainViewController = /* your main controller */
[windowController addWindowController:familyController atIndex:1];// add newcontroller to window controller
UIViewController *partialScreenModalController = /* whatever */
[windowController addWindowController:partialScreenModalController atIndex:2 withCompletion:nil];
// add new UIView to the window
UIView *customAlertView = /* as you will */
[windowController addWindowView:customAlertView atIndex:100];
typedef void (^DRWindowCompletionBlock)();
@interface DRWindowController : UIViewController
// Adding new views
- (void)addWindowView:(UIView *)view atIndex:(NSInteger)index;
- (void)addWindowController:(UIViewController *)controller atIndex:(NSInteger)index;
- (void)addWindowController:(UIViewController *)controller atIndex:(NSInteger)index withCompletion:(DRWindowCompletionBlock)handler options:(NSInteger)options; // todo:make a typedef
- (void)addWindowController:(UIViewController *)controller atIndex:(NSInteger)index withCompletion:(DRWindowCompletionBlock)handler;
// Removing views
- (void)removeWindowView:(UIView *)view;
- (void)removeWindowController:(UIViewController *)controller;
- (void)removeAllControllers;
@end