iOS开发中的ViewController转场切换效果实现简介
在iOS7之前，View Controller的切换主要有4种：
- Push/Pop，NavigationViewController
- Present and dismis Modal
- UITabBarController
- addChildViewController(一般用于自定义的继承于 UIViewController 的容器子类)
iOS5,调用- (void)transitionFromViewController:(UIViewController *)fromViewController toViewController:(UIViewController *)toViewController duration:(NSTimeInterval)duration options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion NS_AVAILABLE_IOS(5_0);
(1)前面3种方法这里就不多说了,很常见的系统方法.至于第四种,我在前面文章-剖析网易标签栏的效果中已经做了阐述,但是它提供的容器转场动画只可以实现一些简单的UIView动画，但是难以重用，耦合高.
(2)关键的API:
A.动画控制器 (Animation Controllers) 遵从 UIViewControllerAnimatedTransitioning 协议，并且负责实际执行动画。
B.交互控制器 (Interaction Controllers) 通过遵从 UIViewControllerInteractiveTransitioning 协议来控制可交互式的转场。
C.转场代理 (Transitioning Delegates) 根据不同的转场类型方便的提供需要的动画控制器和交互控制器。
其中UINavigationControllerDelegate delegate 中新增了2个方法给NavigationController
UIViewControllerTransitioningDelegate 新增transitioningDelegate 给Modal的Present和Dismis
%s__%d__|%@",__FUNCTION__,__LINE__,@"右边");
self.selectedViewController = selectedViewController;
} else if (swipeGestureRecognizer.direction == UISwipeGestureRecognizerDirectionRight){
NSLog(@"%s__%d__|%@",__FUNCTION__,__LINE__,@"左边");
if (_currentControllerIndex > 0) {
_currentControllerIndex--;
}
UIViewController *selectedViewController = self.viewControllers[_currentControllerIndex];
self.selectedViewController = selectedViewController;
}
}
// 重写selectedViewController的setter
- (void)setSelectedViewController:(UIViewController *)selectedViewController
{
NSParameterAssert (selectedViewController);
[self _transitionToChildViewController:selectedViewController];
_selectedViewController = selectedViewController;
}
// 切换操作(自定义的,联想我在前面文章网易标签栏切换中,系统给的transitionFromViewController,是一个道理)
- (void)_transitionToChildViewController:(UIViewController *)toViewController
{
UIViewController *fromViewController = self.childViewControllers.count > 0 ? self.childViewControllers[0] : nil;
if (toViewController == fromViewController) {
return;
}
UIView *toView = toViewController.view;
[toView setTranslatesAutoresizingMaskIntoConstraints:YES];
toView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
toView.frame = self.view.bounds;
// 自定义容器的切换,addChildViewController是关键,它保证了你想要显示的VC能够加载到容器中
// 而所谓的动画和上下文,只是为了转场的动画效果
// 因此,就算用UIScrollView切换,也不能缺少addChildViewController,切记!切记!
[fromViewController willMoveToParentViewController:nil];
[self addChildViewController:toViewController];
if (!fromViewController) {
[self.view addSubview:toViewController.view];
[toViewController didMoveToParentViewController:self];
return;
}
// Animator
FTMthTransitionAnimator *transitionAnimator = [[FTMthTransitionAnimator alloc] init];
NSUInteger fromIndex = [self.viewControllers indexOfObject:fromViewController];
NSUInteger toIndex = [self.viewControllers indexOfObject:toViewController];
// Context
FTMthTransitionContext *transitionContext = [[FTMthTransitionContext alloc] initWithFromViewController:fromViewController toViewController:toViewController goingRight:(toIndex > fromIndex)];
transitionContext.animated = YES;
transitionContext.interactive = NO;
transitionContext.completionBlock = ^(BOOL didComplete) {
// 因为是非交互式,所以fromVC可以直接直接remove出its parent's children controllers array
[fromViewController.view removeFromSuperview];
[fromViewController removeFromParentViewController];
[toViewController didMoveToParentViewController:self];
if ([transitionAnimator respondsToSelector:@selector (animationEnded:)]) {
[transitionAnimator animationEnded:didComplete];
}
};
// 转场动画需要以转场上下文为依托,因为我们是自定义的Context,所以要手动设置
[transitionAnimator animateTransition:transitionContext];
}
大功告成.
上面展示的就是一个基本的自定义容器的非交互式的转场切换.那交互式的呢?从上面我定义手势定义为swip而不是pan也可以看出,非交互转场,并不能完全实现UIScrollView那种分页式的效果,按照类似百分比的形式来进行fromVC和toVC的切换,因为我们缺少交互控制器.在自定义的容器中,系统是没有提供返回交互控制器的协议给我们的,查了蛮多资料,也没找到给出明确的方法,我认为,要跟实现转场上下文一样,仿照系统方法,自定义的去实现交互式的协议方法.我们就要去思考,系统是如何搭建起这个环境的.
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