再谈iOS 7的手势滑动返回功能

再谈iOS 7的手势滑动返回功能

分类： iOS 2014-06-03 20:00 12793人阅读 评论(2) 收藏 举报

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。

[cpp] view plaincopy

1. if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {  
2.     self.navigationController.interactivePopGestureRecognizer.enabled = NO;  
3. }  

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：

[cpp] view plaincopy

1. - (void)viewDidLoad  
2. {  
3.     [super viewDidLoad];  
4.     // Do any additional setup after loading the view.  
5.       
6.     __weak typeof (self) weakSelf = self;  
7.     if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)]) {  
8.         self.interactivePopGestureRecognizer.delegate = weakSelf;  
9.     }  
10. }  

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：

[cpp] view plaincopy

1. - (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated  
2. {    
3.     // fix 'nested pop animation can result in corrupted navigation bar'  
4.     if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)]) {  
5.         self.interactivePopGestureRecognizer.enabled = NO;  
6.     }  
7.       
8.     [super pushViewController:viewController animated:animated];  
9. }  

[cpp] view plaincopy

1. - (void)navigationController:(UINavigationController *)navigationController  
2.        didShowViewController:(UIViewController *)viewController  
3.                     animated:(BOOL)animated  
4. {  
5.     if ([navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {  
6.         navigationController.interactivePopGestureRecognizer.enabled = YES;  
7.     }  
8. }  

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）：

[cpp] view plaincopy

1. - (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController  
2.                                   animationControllerForOperation:(UINavigationControllerOperation)operation  
3.                                                fromViewController:(UIViewController *)fromVC  
4.                                                  toViewController:(UIViewController *)toVC  
5. {  
6.     if (operation == UINavigationControllerOperationPop) {  
7.         if (self.popAnimator == nil) {  
8.             self.popAnimator = [WQPopAnimator new];  
9.         }  
10.         return self.popAnimator;  
11.     }  
12.       
13.     return nil;  
14. }  
15.   
16. - (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController  
17.                          interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController  
18. {  
19.     return self.popInteractionController;  
20. }  
21.   
22. #pragma mark -   
23.   
24. - (void)enablePanToPopForNavigationController:(UINavigationController *)navigationController  
25. {  
26.     UIScreenEdgePanGestureRecognizer *left2rightSwipe = [[UIScreenEdgePanGestureRecognizer alloc]  
27.                                                          initWithTarget:self  
28.                                                          action:@selector(didPanToPop:)];  
29.     //[left2rightSwipe setDelegate:self];  
30.     [left2rightSwipe setEdges:UIRectEdgeLeft];  
31.     [navigationController.view addGestureRecognizer:left2rightSwipe];  
32.       
33.     self.popAnimator = [WQPopAnimator new];  
34.     self.supportPan2Pop = YES;  
35. }  
36.   
37. - (void)didPanToPop:(UIPanGestureRecognizer *)panGesture  
38. {  
39.     if (!self.supportPan2Pop) return ;  
40.       
41.     UIView *view = self.navigationController.view;  
42.       
43.     if (panGesture.state == UIGestureRecognizerStateBegan) {  
44.         self.popInteractionController = [UIPercentDrivenInteractiveTransition new];  
45.         [self.navigationController popViewControllerAnimated:YES];  
46.     } else if (panGesture.state == UIGestureRecognizerStateChanged) {  
47.         CGPoint translation = [panGesture translationInView:view];  
48.         CGFloat d = fabs(translation.x / CGRectGetWidth(view.bounds));  
49.         [self.popInteractionController updateInteractiveTransition:d];  
50.     } else if (panGesture.state == UIGestureRecognizerStateEnded) {  
51.         if ([panGesture velocityInView:view].x > 0) {  
52.             [self.popInteractionController finishInteractiveTransition];  
53.         } else {  
54.             [self.popInteractionController cancelInteractiveTransition];  
55.         }  
56.         self.popInteractionController = nil;  
57.     }  
58. }  

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：

[cpp] view plaincopy

1. - (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController  
2.                                   animationControllerForOperation:(UINavigationControllerOperation)operation  
3.                                                fromViewController:(UIViewController *)fromVC  
4.                                                  toViewController:(UIViewController *)toVC  
5. {  
6.     if (operation == UINavigationControllerOperationPop) {  
7.         if (self.popAnimator == nil) {  
8.             self.popAnimator = [WQPopAnimator new];  
9.         }  
10.         return self.popAnimator;  
11.     }  
12.       
13.     return nil;  
14. }  

而下面这个代理方法则是提供交互式动画：

[cpp] view plaincopy

1. - (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController  
2.                          interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController  
3. {  
4.     return self.popInteractionController;  
5. }  

这两个组合起来使用。首先，我们需要有个动画：

[cpp] view plaincopy

1. @interface WQPopAnimator : NSObject <UIViewControllerAnimatedTransitioning>  
2.   
3. @end  

[cpp] view plaincopy

1. #import "WQPopAnimator.h"  
2.   
3. @implementation WQPopAnimator  
4.   
5. - (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext  
6. {  
7.     return 0.4;  
8. }  
9.   
10. - (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext  
11. {  
12.     UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];  
13.     UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];  
14.     [[transitionContext containerView] insertSubview:toViewController.view belowSubview:fromViewController.view];  
15.       
16.     __block CGRect toRect = toViewController.view.frame;  
17.     CGFloat originX = toRect.origin.x;  
18.     toRect.origin.x -= toRect.size.width / 3;  
19.     toViewController.view.frame = toRect;  
20.       
21.     [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{  
22.         CGRect fromRect = fromViewController.view.frame;  
23.         fromRect.origin.x += fromRect.size.width;  
24.         fromViewController.view.frame = fromRect;  
25.           
26.         toRect.origin.x = originX;  
27.         toViewController.view.frame = toRect;  
28.     } completion:^(BOOL finished) {  
29.         [transitionContext completeTransition:![transitionContext transitionWasCancelled]];  
30.     }];  
31. }  
32.   
33. @end  

其次，交互式动画是通过

[cpp] view plaincopy

1. UIPercentDrivenInteractiveTransition  

来维护的，在滑动过程中根据滑动距离来进行更新：

[cpp] view plaincopy

1. } else if (panGesture.state == UIGestureRecognizerStateChanged) {  
2.         CGPoint translation = [panGesture translationInView:view];  
3.         CGFloat d = fabs(translation.x / CGRectGetWidth(view.bounds));  
4.         [self.popInteractionController updateInteractiveTransition:d];  

当手势结束时要做出收尾动作：

[cpp] view plaincopy

1. } else if (panGesture.state == UIGestureRecognizerStateEnded) {  
2.         if ([panGesture velocityInView:view].x > 0) {  
3.             [self.popInteractionController finishInteractiveTransition];  
4.         } else {  
5.             [self.popInteractionController cancelInteractiveTransition];  
6.         }  
7.         self.popInteractionController = nil;  
8.     }  

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：

[cpp] view plaincopy

1. - (void)navigationController:(UINavigationController *)navigationController  
2.        didShowViewController:(UIViewController *)viewController  
3.                     animated:(BOOL)animated  
4. {  
5.     if (viewController == self.navigationController.pushingViewController) {  
6.         self.supportPan2Pop = YES;  
7.         self.navigationController.pushingViewController = nil;  
8.     }  

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。

• 上一篇Inside ARC — to see the code inserted by the compiler
• 下一篇随手记UIKit Dynamics

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