Custom Container View Controller
2015-02-06 09:19
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转自Luke的博客
什么是Container View Controller?苹果文档是这么描述的:
A container view controller contains content owned by other view controllers. |
在iOS 5之前苹果是不允许出现自定义的Container的 ,也就是说你创建的一个View Controller的view不能包含另一个View Controller的view,这对于逻辑复杂的界面来说,不易于功能拆分。也许曾经你为了某个公用的显示逻辑,直接将某个View Controller的view添加到另一个View Controller的view上,然后发现可以正常显示和使用,但实际上这种行为是非常危险的。
iOS 5.0 开始支持Custom Container View Controller,开放了用于构建自定义Container的接口。如果你想创建一个自己的Container,那么有一些概念还得弄清楚。Container的主要职责就是管理一个或多个Child View Controller的展示的生命周期,需要传递显示以及旋转相关的回调。
其实显示或者旋转的回调的触发的源头来自于window,一个app首先有一个主window,初始化的时候需要给这个主window指定一个rootViewController,window会将显示相关的回调(viewWillAppear:, viewWillDisappear:, viewDidAppear:, or viewDidDisappear: )以及旋转相关的回调(willRotateToInterfaceOrientation:duration: ,willAnimateRotationToInterfaceOrientation:duration:,
didRotateFromInterfaceOrientation:)传递给rootViewController。rootViewController需要再将这些callbacks的调用传递给它的Child View Controllers。
一. 父子关系范式
实现一个Custom Container View Controller并不是一个简单的事情,主要分为两个阶段:父子关系的建立以及父子关系的解除。如果pVC将cVC的view添加为自己的subview,那么cVC必须为pVC的Child View Controller,而反过来则不一定成立,比如UINavigationController,一个View Controller被push进来后便和navigationController建立父子关系了,但是只有最上面的View Controller 是显示着的,底下的View
Controller的view则被移出了容器的view的显示层级,当一个View Controller被pop之后,便和navigationController解除了父子关系了。
展示一个名为content的child view controller:
[self addChildViewController:content]; //1 content.view.frame = [self frameForContentController]; [self.view addSubview:self.currentClientView]; //2 [content didMoveToParentViewController:self]; //3
1.将content添加为child view controller,addChildViewController:接口建立了逻辑上的父子关系,子可以通过parentViewController,访问其父VC,addChildViewController:接口的逻辑中会自动调用 [content willMoveToParentViewController:self];
2.建立父子关系后,便是将content的view加入到父VC的view hierarchy上,同时要决定的是 content的view显示的区域范围。
3.调用child的 didMoveToParentViewController: ,以通知child,完成了父子关系的建立
移除一个child view controller:
[content willMoveToParentViewController:nil]; //1 [content.view removeFromSuperview]; //2 [content removeFromParentViewController]; //3
1.通知child,即将解除父子关系,从语义上也可以看出 child的parent即将为nil
2.将child的view从父VC的view的hierarchy中移除
3.通过removeFromParentViewController的调用真正的解除关系,removeFromParentViewController会自动调用 [content didMoveToParentViewController:nil]
二. appearance callbacks的传递
上面的实现中有一个问题,就是没看到那些appearance callbacks是如何传递的,答案就是appearance callbacks默认情况下是自动调用的,苹果框架底层帮你实现好了,也就是在上面的addSubview的时候,在subview真正加到父view之前,child的viewWillAppear将被调用,真正被add到父view之后,viewDidAppear会被调用。移除的过程中viewWillDisappear,viewDidDisappear的调用过程也是类似的。
有时候自动的appearance callbacks的调用并不能满足需求,比如child view的展示有一个动画的过程,这个时候我们并不想viewDidAppear的调用在addSubview的时候进行,而是等展示动画结束后再调用viewDidAppear。
也许你可能会提到 transitionFromViewController:toViewController:duration:options:animations:completion: 这个方法,会帮你自动处理view的add和remove,以及支持animations block,也能够保证在动画开始前调用willAppear或者willDisappear,在调用结束的时候调用didAppear,didDisappear,但是此方式也存在局限性,必须是两个新老子VC的切换,都不能为空,因为要保证新老VC拥有同一个parentViewController,且参数中的viewController不能是系统中的container,比如不能是UINavigationController或者UITabbarController等。
所以如果你要自己写一个界面容器往往用不了appearence callbacks自动调用的特性,需要将此特性关闭,然后自己去精确控制appearance callbacks的调用时机。
那如何关闭appearance callbacks的自动传递的特性呢?
在iOS 5.x中你需要覆盖automaticallyForwardAppearanceAndRotationMethodsToChildViewControllers,然后返回NO,iOS6+中你需要覆盖 shouldAutomaticallyForwardAppearanceMethods方法并返回NO。
手动传递的时候你并不能直接去调用child 的viewWillAppear或者viewDidAppear这些方法,而是需要使用 beginAppearanceTransition:animated:和endAppearanceTransition接口来间接触发那些appearance callbacks,且begin和end必须成对出现。
[content beginAppearanceTransition:YES animated:animated]触发content的viewWillAppear,[content beginAppearanceTransition:NO animated:animated]触发content的viewWillDisappear,和他们配套的[content endAppearanceTransition]分别触发viewDidAppear和viewDidDisappear。 (AppearanceTransition的这两个接口之前在苹果描述的文档中一开始还存在问题,因为文档中一开始说是iOS5不支持这两个接口,其实是支持的,后来苹果纠正了文档中的这个错误)。
三. rotation callbacks的传递
也许在iPhone上很少要关心的屏幕旋转问题的,但是大屏幕的iPad上就不同了,很多时候你需要关心横竖屏。rotation callbacks 一般情况下只需要关心三个方法 willRotateToInterfaceOrientation:duration:在旋转开始前,此方法会被调用;willAnimateRotationToInterfaceOrientation:duration: 此方法的调用在旋转动画block的内部,也就是说在此方法中的代码会作为旋转animation block的一部分;didRotateFromInterfaceOrientation:此方法会在旋转结束时被调用。而作为view
controller container 就要肩负起旋转的决策以及旋转的callbacks的传递的责任。
当使用框架的自动传递的特性的时候,作为容器的view controller 会自动 将这些方法传递给所有的child viewcontrollers, 有时候你可能不需要传递给所有的child viewcontroller,而只需要传递给正在显示的child viewcontroller,那么你就需要禁掉旋转回调自动传递的特性,和禁掉appearance callbacks自动传递的方式类似,需要覆盖相关方法并返回NO,在iOS5.x中,appearance callbacks和rotation callbacks禁掉是公用一个方法的就是
automaticallyForwardAppearanceAndRotationMethodsToChildViewControllers,在iOS6之后分成两个独立的方法,旋转的则是 shouldAutomaticallyForwardRotationMethods。
旋转相关的除了上面的几个rotation callbacks方法外,还有一个十分重要的概念,就是一个view controller可以决定自己是否支持当前取向的旋转,这个东西在iOS6前后的实现方式还不一样,iOS6之前使用的方法是 shouldAutorotateToInterfaceOrientation,就是一个view controller覆盖此方法,根据传入的即将旋转的取向的参数,来决定是否旋转。而iOS6.0之后的实现则拆分成两个方法 shouldAutorotate和supportedInterfaceOrientations,前者决定再旋转的时候是否去根据supportedInterfaceOrientations所支持的取向来决定是否旋转,也就是说如果shouldAutorotate返回YES的时候,才会去调用supportedInterfaceOrientations检查当前view
controller支持的取向,如果当前取向在支持的范围中,则进行旋转,如果不在则不旋转;而当shouldAutorotate返回NO的时候,则根本不会去管supportedInterfaceOrientations这个方法,反正是不会跟着设备旋转就是了。
而作为界面容器你要注意的就是你需要去检查你的child view controller,检查他们对横竖屏的支持情况,以便容器自己决策在横竖屏旋转时候是否支持当前的取向,和上面的callbacks传递的方向相比,这其实是一个反向的传递。
四. 创建自己的容器基类
当你需要构建自己的Container View Controller的时候,每一个Container都会有一些相同的逻辑,如果你每一个都写一遍会存在很多重复代码,所以最好你创建一个Container基类,去实现容器都需要的逻辑。那到底有哪些逻辑是每一个Container都需要做的呢?关闭Appearance和Rotation相关方法的自动传递;当Container的Appearance和Rotation相关方法被调用时,需要将方法传递给相关的Child View Controller;以及当前Container是否支持旋转的决策逻辑等。下面为一个容器基类的示范:
#import "ContainerBaseController.h" @implementation ContainerBaseController #pragma mark - #pragma mark Overrides //NS_DEPRECATED_IOS(5_0,6_0) - (BOOL)automaticallyForwardAppearanceAndRotationMethodsToChildViewControllers{ return NO; } //NS_AVAILABLE_IOS(6_0) - (BOOL)shouldAutomaticallyForwardAppearanceMethods{ return NO; } //NS_AVAILABLE_IOS(6_0) - (BOOL)shouldAutomaticallyForwardRotationMethods{ return NO; } - (void)viewWillAppear:(BOOL)animated{ [super viewWillAppear:animated]; NSArray *viewControllers = [self childViewControllersWithAppearanceCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController beginAppearanceTransition:YES animated:animated]; } } - (void)viewDidAppear:(BOOL)animated{ [super viewDidAppear:animated]; NSArray *viewControllers = [self childViewControllersWithAppearanceCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController endAppearanceTransition]; } } - (void)viewWillDisappear:(BOOL)animated{ [super viewWillDisappear:animated]; NSArray *viewControllers = [self childViewControllersWithAppearanceCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController beginAppearanceTransition:NO animated:animated]; } } - (void)viewDidDisappear:(BOOL)animated{ [super viewDidDisappear:animated]; NSArray *viewControllers = [self childViewControllersWithAppearanceCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController endAppearanceTransition]; } } - (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration{ [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration]; NSArray *viewControllers = [self childViewControllersWithRotationCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration]; } } - (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration{ [super willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration]; NSArray *viewControllers = [self childViewControllersWithRotationCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration]; } } - (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation{ [super didRotateFromInterfaceOrientation:fromInterfaceOrientation]; NSArray *viewControllers = [self childViewControllersWithRotationCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { [viewController didRotateFromInterfaceOrientation:fromInterfaceOrientation]; } } /* NS_AVAILABLE_IOS(6_0) 向下查看和旋转相关的ChildViewController的shouldAutorotate的值 只有所有相关的子VC都支持Autorotate,才返回YES */ - (BOOL)shouldAutorotate{ NSArray *viewControllers = [self childViewControllersWithRotationCallbackAutoForward]; BOOL shouldAutorotate = YES; for (UIViewController *viewController in viewControllers) { shouldAutorotate = shouldAutorotate && [viewController shouldAutorotate]; } return shouldAutorotate; } /* NS_AVAILABLE_IOS(6_0) 此方法会在设备旋转且shouldAutorotate返回YES的时候才会被触发 根据对应的所有支持的取向来决定是否需要旋转 作为容器,支持的取向还决定于自己的相关子ViewControllers */ - (NSUInteger)supportedInterfaceOrientations{ NSUInteger supportedInterfaceOrientations = UIInterfaceOrientationMaskAll; NSArray *viewControllers = [self childViewControllersWithRotationCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { supportedInterfaceOrientations = supportedInterfaceOrientations & [viewController supportedInterfaceOrientations]; } return supportedInterfaceOrientations; } /* NS_DEPRECATED_IOS(2_0, 6_0) 6.0以下,设备旋转时,此方法会被调用 用来决定是否要旋转 */ - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation{ BOOL shouldAutorotate = YES; NSArray *viewControllers = [self childViewControllersWithRotationCallbackAutoForward]; for (UIViewController *viewController in viewControllers) { shouldAutorotate = shouldAutorotate && [viewController shouldAutorotateToInterfaceOrientation:toInterfaceOrientation]; } return shouldAutorotate; } #pragma mark - #pragma mark 下面两个方法是在需要的情况下给基类覆盖用的,毕竟不是所有的容器都需要将相关方法传递给所有的childViewControllers - (NSArray *)childViewControllersWithAppearanceCallbackAutoForward{ return self.childViewControllers; } - (NSArray *)childViewControllersWithRotationCallbackAutoForward{ return self.childViewControllers; } @end
五. 创建自己的Container
设计要点
创建一个Container,首先你得设计好Container View Controller的行为和公开的API,你可以好好参考UIKit中自带的一些Container的设计风格,比如UINaivgationController就是管理着一组Content View Controller的堆栈的Container,且正在显示的是栈顶的View Controller。
主要接口有View Controller的推入,此过程中viewController会和navigationController建立父子关系,并将viewController显示出来,如果animated是YES的话,则会有过场动画:
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
pop操作,移除栈顶的内容,会解除和navigationController的父子关系:
- (UIViewController *)popViewControllerAnimated:(BOOL)animated;
当然关于pop还有一些其他的便捷接口,这里就不赘述了。
另外需要提供一些快捷的接口方便获取特定的Child View Controller,比如topViewController可以获取栈顶的View Controller。
另外如有必要,Container还需要留有delegate接口,便于通知外面Container的相关行为阶段,便于外部做出相关操作,比如UINaivgationController就会在即将要push一个新的View Controller,已经push了一个新的View Controller等时机留有delegate方法。
还有一个需要考虑的问题就是直接或者间接的Child View Controller如何快速的检索到相应的Container呢?一般Container在实现的时候就需要考虑此问题并提供相应的接口,实现的方法一般就是实现一个UIViewController的Category,比如UINavigationController,在某个View Controller中访问其navigationController属性,会向上遍历,直到找到最近的类型为UINavigationController的祖先,如果找不到则为nil:
@interface UIViewController (UINavigationControllerItem) ... @property(nonatomic,readonly,retain) UINavigationController *navigationController; @end
实现一个简单的模态窗口Container
模态展示 则至少存在present,dismiss的接口,以及获取模态View Controller的属性 :
#import <UIKit/UIKit.h> #import "ContainerBaseController.h" @interface SimpleModalContainerController : ContainerBaseController @property (nonatomic, readonly) UIViewController *simpleModalViewController; - (void)presentSimpleModalViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)animated; - (void)dismissSimpleModalViewControllerAnimated:(BOOL)animated; @end //实现如下 #import "SimpleModalContainerController.h" @interface SimpleModalContainerController () @property (nonatomic, readwrite) UIViewController *simpleModalViewController; @property (nonatomic, strong) UIButton *backgroundButton; @end @implementation SimpleModalContainerController - (void)buttonTapped:(id)sender{ [self dismissSimpleModalViewControllerAnimated:YES]; } - (UIButton *)backgroundButton{ if (!_backgroundButton) { _backgroundButton = [UIButton buttonWithType:UIButtonTypeCustom]; _backgroundButton.backgroundColor = [UIColor blackColor]; _backgroundButton.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight; _backgroundButton.alpha = 0.3; [_backgroundButton addTarget:self action:@selector(buttonTapped:) forControlEvents:UIControlEventTouchUpInside]; } _backgroundButton.frame = self.view.bounds; return _backgroundButton; } - (void)presentSimpleModalViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)animated{ if (!self.simpleModalViewController && viewControllerToPresent) { self.simpleModalViewController = viewControllerToPresent; [self addChildViewController:viewControllerToPresent]; [viewControllerToPresent beginAppearanceTransition:YES animated:animated]; [self.view addSubview:self.backgroundButton]; viewControllerToPresent.view.center = CGPointMake(CGRectGetWidth(self.view.bounds) / 2.0, CGRectGetHeight(self.view.bounds) / 2.0); [self.view addSubview:viewControllerToPresent.view]; if (animated) { viewControllerToPresent.view.alpha = 0; self.backgroundButton.alpha = 0; [UIView animateWithDuration:0.3 animations:^{ viewControllerToPresent.view.alpha = 1; self.backgroundButton.alpha = 0.3; } completion:^(BOOL finished) { [viewControllerToPresent endAppearanceTransition]; [viewControllerToPresent didMoveToParentViewController:self]; }]; } else { self.backgroundButton.alpha = 0.3; [viewControllerToPresent endAppearanceTransition]; [viewControllerToPresent didMoveToParentViewController:self]; } } } - (void)dismissSimpleModalViewControllerAnimated:(BOOL)animated{ if (self.simpleModalViewController) { [self.simpleModalViewController willMoveToParentViewController:nil]; [self.simpleModalViewController beginAppearanceTransition:NO animated:animated]; if (animated) { [UIView animateWithDuration:0.3 animations:^{ self.backgroundButton.alpha = 0; self.simpleModalViewController.view.alpha = 0 ; } completion:^(BOOL finished) { [self.backgroundButton removeFromSuperview]; [self.simpleModalViewController.view removeFromSuperview]; self.simpleModalViewController.view.alpha = 1.0; [self.simpleModalViewController endAppearanceTransition]; [self.simpleModalViewController removeFromParentViewController]; self.simpleModalViewController = nil; }]; } else { [self.backgroundButton removeFromSuperview]; [self.simpleModalViewController.view removeFromSuperview]; self.simpleModalViewController.view.alpha = 1.0; [self.simpleModalViewController endAppearanceTransition]; [self.simpleModalViewController removeFromParentViewController]; self.simpleModalViewController = nil; } } } @end
UIViewController的Category用于Child View Controller 获取上层的SimpleModalContainerController :
@interface UIViewController (SimpleModalContainerController) @property (nonatomic, readonly) SimpleModalContainerController *simpleModalContainerController; @end @implementation UIViewController (SimpleModalContainerController) - (SimpleModalContainerController *)simpleModalContainerController{ for (UIViewController *viewController = self.parentViewController; viewController != nil; viewController = viewController.parentViewController) { if ([viewController isKindOfClass:[SimpleModalContainerController class]]) { return (SimpleModalContainerController *)viewController; } } return nil; } @end
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