上一篇记录了利用系统私有变量和方法实现右滑返回手势功能：http://www.cnblogs.com/ALongWay/p/5893515.html
这篇继续记录另一种方案：利用UINavigationController的delegate方法。
核心代理方法有如下两个：
- (nullable id <UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController
interactionControllerForAnimationController:(id <UIViewControllerAnimatedTransitioning>) animationController NS_AVAILABLE_IOS(7_0); - (nullable id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
animationControllerForOperation:(UINavigationControllerOperation)operation
fromViewController:(UIViewController *)fromVC
toViewController:(UIViewController *)toVC NS_AVAILABLE_IOS(7_0);
第一个代理方法，要求在视图控制器变换时候，返回一个实现UIViewControllerInteractiveTransitioning协议的对象，该对象用于控制交互进度和状态。
UIKit.h/UIViewControllerTransitioning.h中已经准备好了一个这样的对象，名为UIPercentDrivenInteractiveTransition。
主要关注其如下三个方法：
- (void)updateInteractiveTransition:(CGFloat)percentComplete;//控制交互进度的百分比
- (void)cancelInteractiveTransition;//中途取消交互
- (void)finishInteractiveTransition;//完成交互
可以在一个实现了代理方法的类中，定义一个手势目标方法来调用上述方法，达到控制作为变量的UIPercentDrivenInteractiveTransition对象的目的。
主要代码如下：
- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController
{
if ([animationController isKindOfClass:[PopAnimation class]])
return _interactivePopTransition; return nil;
} - (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC
{
if (operation == UINavigationControllerOperationPop)
return _popAnimation; return nil;
} - (void)handlePopGestureOperation:(UIPanGestureRecognizer *)recognizer{
//将手指在屏幕上的移动距离与屏幕宽度比例作为动画的进度
CGPoint translationInScreen = [recognizer translationInView:[UIApplication sharedApplication].keyWindow];
CGFloat progress = translationInScreen.x / [UIScreen mainScreen].bounds.size.width;
progress = MIN(1.0, MAX(0.0, progress)); if (recognizer.state == UIGestureRecognizerStateBegan) {
//新建手势交互对象
_interactivePopTransition = [[UIPercentDrivenInteractiveTransition alloc] init]; //开始执行pop动画
[_naviController popViewControllerAnimated:YES];
}else if (recognizer.state == UIGestureRecognizerStateChanged) {
//更新进度
[_interactivePopTransition updateInteractiveTransition:progress];
}else if (recognizer.state == UIGestureRecognizerStateEnded
|| recognizer.state == UIGestureRecognizerStateCancelled) {
//手势结束时如果进度大于一半，那么就完成pop操作，否则取消
if (progress > 0.5) {
[_interactivePopTransition finishInteractiveTransition];
}else {
[_interactivePopTransition cancelInteractiveTransition];
} //手势交互结束，清理对象
_interactivePopTransition = nil;
}
}
第二个代理方法，要求在操作开始时候，返回一个实现UIViewControllerAnimatedTransitioning协议的对象，该对象实现了动画内容和执行时间。
该协议有三个方法：
// This is used for percent driven interactive transitions, as well as for container controllers that have companion animations that might need to
// synchronize with the main animation.
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;
// This method can only be a nop if the transition is interactive and not a percentDriven interactive transition.
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext; @optional // This is a convenience and if implemented will be invoked by the system when the transition context's completeTransition: method is invoked.
- (void)animationEnded:(BOOL) transitionCompleted;
第一个方法返回动画时间；第二个方法，可以得到实现了UIViewControllerContextTransitioning协议的对象；第三个方法可选，如果transitionContext对象调用了completeTransition：方法，该代理方法会被调用。
重点是第二个方法的transitionContext对象，其重要的方法如下：
// The view in which the animated transition should take place.
- (nullable UIView *)containerView;//动画所在的容器view
- (BOOL)transitionWasCancelled;//转换是否取消// This must be called whenever a transition completes (or is cancelled.)
// Typically this is called by the object conforming to the
// UIViewControllerAnimatedTransitioning protocol that was vended by the transitioning
// delegate. For purely interactive transitions it should be called by the
// interaction controller. This method effectively updates internal view
// controller state at the end of the transition.
- (void)completeTransition:(BOOL)didComplete;//完成转换，必须在动画完成时调用 // Currently only two keys are defined by the
// system - UITransitionContextToViewControllerKey, and
// UITransitionContextFromViewControllerKey.
// Animators should not directly manipulate a view controller's views and should
// use viewForKey: to get views instead.
- (nullable __kindof UIViewController *)viewControllerForKey:(NSString *)key;//取得视图控制器 // Currently only two keys are defined by the system -
// UITransitionContextFromViewKey, and UITransitionContextToViewKey
// viewForKey: may return nil which would indicate that the animator should not
// manipulate the associated view controller's view.
- (nullable __kindof UIView *)viewForKey:(NSString *)key NS_AVAILABLE_IOS(8_0);//取得视图控制器的view，兼容iOS7，可以直接用上面取到的viewController.view
创建一个实现UIViewControllerAnimatedTransitioning协议的对象PopAnimation，重要代码如下：
- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext {
return _transitionDuration;
}
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext {
_transitionContext = transitionContext;
//当前控制器
UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
//动画结束显示的控制器
UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
//执行交互动画的容器view
UIView *containerView = [transitionContext containerView];
[containerView insertSubview:toViewController.view belowSubview:fromViewController.view];
NSTimeInterval duration = [self transitionDuration:transitionContext];
switch (_popAnimationType) {
case PopAnimationTranslation: {
CGFloat containerWidth = containerView.frame.size.width;
toViewController.view.transform = CGAffineTransformMakeTranslation(-containerWidth / 4.0, );
[UIView animateWithDuration:duration animations:^{
toViewController.view.transform = CGAffineTransformMakeTranslation(, );
fromViewController.view.transform = CGAffineTransformMakeTranslation(containerWidth, );
}completion:^(BOOL finished) {
//动画结束，必须调用此方法
[transitionContext completeTransition:!transitionContext.transitionWasCancelled];
}];
break;
}
case PopAnimationFlip: {
[UIView beginAnimations:@"View Flip" context:nil];
[UIView setAnimationDuration:duration];
[UIView setAnimationDelegate:self];
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:containerView cache:YES];
[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:)];
[UIView commitAnimations];
[containerView exchangeSubviewAtIndex: withSubviewAtIndex:];
break;
}
case PopAnimationCube: {
CATransition *transiton = [CATransition animation];
transiton.type = @"cube";
transiton.subtype = @"fromLeft";
transiton.duration = duration;
transiton.removedOnCompletion = NO;
transiton.fillMode = kCAFillModeForwards;
transiton.delegate = self;
[containerView.layer addAnimation:transiton forKey:nil];
[containerView exchangeSubviewAtIndex: withSubviewAtIndex:];
break;
}
}
}
- (void)animationDidStop:(CATransition *)anim finished:(BOOL)flag {
[_transitionContext completeTransition:!_transitionContext.transitionWasCancelled];
}
剩下的工作：
在上一篇的基础上，修改UINavigationController的base_pushViewController方法
- (void)base_pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
if (![self.interactivePopGestureRecognizer.view.gestureRecognizers containsObject:self.base_panGestureRecognizer]) {
[self.interactivePopGestureRecognizer.view addGestureRecognizer:self.base_panGestureRecognizer]; self.base_panGestureRecognizer.delegate = [self base_panGestureRecognizerDelegateObject]; self.base_currentDelegateObject = [[NavigationControllerDelegateObject alloc] initWithUINavigationController:self]; [self.base_panGestureRecognizer addTarget:self.base_currentDelegateObject action:@selector(handlePopGestureOperation:)]; self.interactivePopGestureRecognizer.enabled = NO;
} [self base_setupViewControllerBasedNavigationBarAppearanceIfNeeded:viewController]; if (![self.viewControllers containsObject:viewController]) {
[self base_pushViewController:viewController animated:animated];
}
}
可以看到，去除了私有变量和方法的调用，自定义了名为NavigationControllerDelegateObject的对象，其实现了UINavigationControllerDelegate协议，并实现了pan手势的处理方法。在此，我暴露了该属性对象，考虑到以后可能会增加或者修改UINavigationControllerDelegate的实现协议，可以为该对象增加分类来达到目的；还有一个目的，便于修改popAnimation的动画类型和执行时间。
总结：
两篇记录，从不同的方向，记录了右滑返回手势功能的实现。利用系统变量和方法，方便快捷；利用协议方法，高度自定义。
但是，利用协议方法，需要处理的方面比较多。虽然上述已经记录了实现核心，示例代码中也有详细代码，但是仍然还有很多方面未考虑。
目前，我发现的一些问题：
1.导航栏交互效果也需要自行实现，暂未实现原生效果
2.导航栏由隐藏到显示的效果，有时会出现异常
3.如果带有bottomBar，效果不理想
如果有好的解决办法，希望告知，谢谢。
base项目已更新：git@github.com:ALongWay/base.git
项目增加了新的UINavigationController+PopOperation分类，但是未引用到项目中，需要的同学，可先删除PopGesture分类的引用，再添加该分类的应用。