iOS中的转场研究(3)
2015-01-04 12:57
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实现自定义的Container View Controller
上一篇文章中提到了如何定制Segue。我们知道Unwind Segue的正常工作需要Container View Controller的支持。我们可以实现:canPerformUnwindSegueAction:fromViewController:withSender:
viewControllerForUnwindSegueAction:fromViewController:withSender:
segueForUnwindingToViewController:fromViewController:identifier:
三个方法来定制自己的Container View Controller(以下简称“容器”)。
我们一般会在子Controller中通过实现
canPerformUnwindSegueAction:fromViewController:withSender:来决定要不要执行相应的Unwind Segue。
在自定义的容器中,我们必须实现
viewControllerForUnwindSegueAction:fromViewController:withSender:和
segueForUnwindingToViewController:fromViewController:identifier:方法。前一个方法用来决定那个View Controller来处理Unwind Segue action,后一个方法用来返回自定义的Unwind Segue实例。
使用Modal presentation时需要注意的情况
当我们使用UIViewController的
presentViewController:animated:completion:方法以Modal presentation的方式来跳转场景的时候,情况与在Navigation View Controller有很大不同。首先,使用这种方式跳转场景的时候,跳转到的View Controller为Source View Controller的子Controller,而在Navigation View Controller中,所有的流程Controller基本上都是Navgation
View Controller的子Controller,所以二者在View Controller的层次管理上有很多不同。因此实现Modal presentation风格的Segue的时候,动画的view不能搞错,必须对View Controller中的顶层View操作。一个参考实现如下(略掉动画效果代码,仅提供转场方法调用代码)1:
Segue部分:
- (UIView *)findTopMostViewForViewController:(UIViewController *)viewController { UIView *theView = viewController.view; UIViewController *parentViewController = viewController.parentViewController; while (parentViewController != nil) { theView = parentViewController.view; parentViewController = parentViewController.parentViewController; } return theView; } - (void)perform { UIViewController *source = self.sourceViewController; UIViewController *destination = self.destinationViewController; // Find the views that we will be animating. If the source or destination // view controller sits inside a container view controller, then the view // to animate will actually be that parent controller's view. UIView *sourceView = [self findTopMostViewForViewController:source]; UIView *destinationView = [self findTopMostViewForViewController:destination]; [source presentViewController:destination animated:NO completion:^{ // completion code here }]; }
Unwind Segue部分:
- (UIView *)findTopMostViewForViewController:(UIViewController *)viewController { UIView *theView = viewController.view; UIViewController *parentViewController = viewController.parentViewController; while (parentViewController != nil) { theView = parentViewController.view; parentViewController = parentViewController.parentViewController; } return theView; } - (void)perform { UIViewController *source = self.sourceViewController; UIViewController *destination = self.destinationViewController; // Find the views that we will be animating. If the source or destination // view controller sits inside a container view controller, then the view // to animate will actually be that parent controller's view. UIView *sourceView = [self findTopMostViewForViewController:source]; UIView *destinationView = [self findTopMostViewForViewController:destination]; [source dismissViewControllerAnimated:NO completion:^{ // completion code here }]; }
注意:Modal Presentation的Unwind Segue很难实现无Bug的任意跳转,因为
UIViewController中,跟Container View Controller相关的方法的默认实现并不能很好的定位Container View Controller。而以正确的方式重写这些方法并不容易。所以如果有任意跳转的需求,我们可以尝试自己实现一个简单的Container View Controller。
使用AddChildViewController API实现自己的Container View Controller
我们偶尔会希望有一个跟Navigation View Controller差不多的容器,但是又不希望像Navigation View Controller那么笨重,且限制多多。我们知道Navigation View Controller在Interface Builder中,其Navigation Bar能容纳的元素样式并不丰富,尽管大多数时候,我们能够通过UIAppearance来定制一些样式,但我们希望定制能容纳更加丰富的元素的Navigation Bar,或者其他定制的导航界面的时候,希望能够实现一个类似的容器。我们当然可以模仿NavigationView Controller的公开API实现一个差不多的东西,如果我们要很方便的使用自定义Segue和任意跳转的Unwind Segue的话,还需要以特定的方式实现上面提到的一些方法。
UIViewController的
addChildViewController:方法同样可以做出类似的功能,而且相比Modal presentation,这种方式代码更加直观。因为使用这个API实现的容器,对子Controller的管理方式与Navigation View
Controller类似。
容器的部分代码如下:
- (UIViewController *)viewControllerForUnwindSegueAction:(SEL)action fromViewController:(UIViewController *)fromViewController withSender:(id)sender { for (UIViewController *childController in self.childViewControllers) { if ([childController canPerformUnwindSegueAction:action fromViewController:fromViewController withSender:sender]) { return childController; } } return nil; } - (UIStoryboardSegue *)segueForUnwindingToViewController:(UIViewController *)toViewController fromViewController:(UIViewController *)fromViewController identifier:(NSString *)identifier { UIStoryboardSegue *unwindSegue = [[MyLeftToRightUnwindSegue alloc] initWithIdentifier:identifier source:fromViewController destination:toViewController]; return unwindSegue; }
Segue代码:
- (BOOL)controllerInStack:(UIViewController *)controller { UIViewController *fromController = self.sourceViewController; UIViewController *containerController = fromController.parentViewController; for (UIViewController *childController in containerController.childViewControllers) { if (childController == controller) { return YES; } } return NO; } - (void)perform { // A simple transition. // New scene slides in from right and old scene slides out to left. UIViewController *fromController = self.sourceViewController; UIViewController *toController = self.destinationViewController; UIViewController *parentController = fromController.parentViewController; UIView *containerView = parentController.view; [containerView addSubview:toController.view]; CGRect initialFromRect = fromController.view.frame; CGRect initialToRect = CGRectOffset(initialFromRect, initialFromRect.size.width, 0); CGRect finalFromRect = CGRectOffset(initialFromRect, -initialFromRect.size.width, 0); CGRect finalToRect = initialFromRect; toController.view.frame = initialToRect; if (![self controllerInStack:toController]) { // notify containment event. [toController willMoveToParentViewController:parentController]; } [UIView animateWithDuration:0.4f animations:^{ fromController.view.frame = finalFromRect; toController.view.frame = finalToRect; } completion:^(BOOL finished) { if (![self controllerInStack:toController]) { // Add new controller as a child controller to the container view controller [parentController addChildViewController:toController]; // notify containment event. [toController didMoveToParentViewController:toController]; } [fromController.view removeFromSuperview]; }]; }
Unwind Segue代码:
- (void)perform { // A simple transition. // New scene slides in from left and old scene slides out to right. UIViewController *fromController = self.sourceViewController; UIViewController *toController = self.destinationViewController; UIViewController *parentController = fromController.parentViewC 9cf1 ontroller; UIView *containerView = parentController.view; [containerView addSubview:toController.view]; CGRect initialFromRect = fromController.view.frame; CGRect initialToRect = CGRectOffset(initialFromRect, -initialFromRect.size.width, 0); CGRect finalFromRect = CGRectOffset(initialFromRect, initialFromRect.size.width, 0); CGRect finalToRect = initialFromRect; toController.view.frame = initialToRect; [UIView animateWithDuration:0.4f animations:^{ fromController.view.frame = finalFromRect; toController.view.frame = finalToRect; } completion:^(BOOL finished) { [fromController.view removeFromSuperview]; }]; }
当我们定义的Container View中有需要置顶的元素(比如定制的导航条)时,可以将
addSubView:方法换成
insertSubView:atIndex:方法来调整子视图的层次。
下面的代码修改自iOS6 by Tutorial中的示例代码。??
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