再谈iOS 7的手势滑动返回功能

http://blog.csdn.net/jasonblog/article/details/28282147

之前随手写过一篇《使用UIScreenEdgePanGestureRecognizer实现swipe to pop效果》，挺粗糙的。

现在使用默认模板创建的iOS App都支持手势返回功能，如果导航栏的返回按钮是自定义的那么则会失效，也可以参考这里手动设置无效。

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if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {

self.navigationController.interactivePopGestureRecognizer.enabled = NO;

}

如果是因为自定义导航按钮而导致手势返回失效，那么可以在NavigationController的viewDidLoad函数中添加如下代码：

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- (void)viewDidLoad

{

[super viewDidLoad];

// Do any additional setup after loading the view.

__weak typeof (self) weakSelf = self;

if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)]) {

self.interactivePopGestureRecognizer.delegate = weakSelf;

}

}

这样写了以后就可以通过手势滑动返回上一层了，但是如果在push过程中触发手势滑动返回，会导致导航栏崩溃（从日志中可以看出）。针对这个问题，我们需要在pop过程禁用手势滑动返回功能：

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- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated

{

// fix 'nested pop animation can result in corrupted navigation bar'

if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)]) {

self.interactivePopGestureRecognizer.enabled = NO;

}

[super pushViewController:viewController animated:animated];

}

[cpp] view
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- (void)navigationController:(UINavigationController *)navigationController

didShowViewController:(UIViewController *)viewController

animated:(BOOL)animated

{

if ([navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {

navigationController.interactivePopGestureRecognizer.enabled = YES;

}

}

除了使用系统默认的动画，还可以使用自定义过渡动画（丰满的文档）：

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- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController

animationControllerForOperation:(UINavigationControllerOperation)operation

fromViewController:(UIViewController *)fromVC

toViewController:(UIViewController *)toVC

{

if (operation == UINavigationControllerOperationPop) {

if (self.popAnimator == nil) {

self.popAnimator = [WQPopAnimator new];

}

return self.popAnimator;

}

return nil;

}

- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController

interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController

{

return self.popInteractionController;

}

#pragma mark -

- (void)enablePanToPopForNavigationController:(UINavigationController *)navigationController

{

UIScreenEdgePanGestureRecognizer *left2rightSwipe = [[UIScreenEdgePanGestureRecognizer alloc]

initWithTarget:self

action:@selector(didPanToPop:)];

//[left2rightSwipe setDelegate:self];

[left2rightSwipe setEdges:UIRectEdgeLeft];

[navigationController.view addGestureRecognizer:left2rightSwipe];

self.popAnimator = [WQPopAnimator new];

self.supportPan2Pop = YES;

}

- (void)didPanToPop:(UIPanGestureRecognizer *)panGesture

{

if (!self.supportPan2Pop) return ;

UIView *view = self.navigationController.view;

if (panGesture.state == UIGestureRecognizerStateBegan) {

self.popInteractionController = [UIPercentDrivenInteractiveTransition new];

[self.navigationController popViewControllerAnimated:YES];

} else if (panGesture.state == UIGestureRecognizerStateChanged) {

CGPoint translation = [panGesture translationInView:view];

CGFloat d = fabs(translation.x / CGRectGetWidth(view.bounds));

[self.popInteractionController updateInteractiveTransition:d];

} else if (panGesture.state == UIGestureRecognizerStateEnded) {

if ([panGesture velocityInView:view].x > 0) {

[self.popInteractionController finishInteractiveTransition];

} else {

[self.popInteractionController cancelInteractiveTransition];

}

self.popInteractionController = nil;

}

}

如下这个代理方法是用来提供一个非交互式的过渡动画的：

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- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController

animationControllerForOperation:(UINavigationControllerOperation)operation

fromViewController:(UIViewController *)fromVC

toViewController:(UIViewController *)toVC

{

if (operation == UINavigationControllerOperationPop) {

if (self.popAnimator == nil) {

self.popAnimator = [WQPopAnimator new];

}

return self.popAnimator;

}

return nil;

}

而下面这个代理方法则是提供交互式动画：

[cpp] view
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- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController

interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController

{

return self.popInteractionController;

}

这两个组合起来使用。首先，我们需要有个动画：

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@interface WQPopAnimator : NSObject <UIViewControllerAnimatedTransitioning>

@end

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#import "WQPopAnimator.h"

@implementation WQPopAnimator

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext

{

return 0.4;

}

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext

{

UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];

[[transitionContext containerView] insertSubview:toViewController.view belowSubview:fromViewController.view];

__block CGRect toRect = toViewController.view.frame;

CGFloat originX = toRect.origin.x;

toRect.origin.x -= toRect.size.width / 3;

toViewController.view.frame = toRect;

[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{

CGRect fromRect = fromViewController.view.frame;

fromRect.origin.x += fromRect.size.width;

fromViewController.view.frame = fromRect;

toRect.origin.x = originX;

toViewController.view.frame = toRect;

} completion:^(BOOL finished) {

[transitionContext completeTransition:![transitionContext transitionWasCancelled]];

}];

}

@end

其次，交互式动画是通过

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UIPercentDrivenInteractiveTransition

来维护的，在滑动过程中根据滑动距离来进行更新：

[cpp] view
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} else if (panGesture.state == UIGestureRecognizerStateChanged) {

CGPoint translation = [panGesture translationInView:view];

CGFloat d = fabs(translation.x / CGRectGetWidth(view.bounds));

[self.popInteractionController updateInteractiveTransition:d];

当手势结束时要做出收尾动作：

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} else if (panGesture.state == UIGestureRecognizerStateEnded) {

if ([panGesture velocityInView:view].x > 0) {

[self.popInteractionController finishInteractiveTransition];

} else {

[self.popInteractionController cancelInteractiveTransition];

}

self.popInteractionController = nil;

}

同样地，自定义的动画也会有上面提到的导航栏崩溃问题，也可以通过类似的方法来解决：

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- (void)navigationController:(UINavigationController *)navigationController

didShowViewController:(UIViewController *)viewController

animated:(BOOL)animated

{

if (viewController == self.navigationController.pushingViewController) {

self.supportPan2Pop = YES;

self.navigationController.pushingViewController = nil;

}

补充：位于当前navgationController的第一个（[0]）viewController时需要设置手势代理，不响应。