再談iOS 7的手勢滑動返回功能

以前隨手寫過一篇《使用UIScreenEdgePanGestureRecognizer實現swipe to pop效果》，挺粗糙的。

如今使用默認模板建立的iOS App都支持手勢返回功能，若是導航欄的返回按鈕是自定義的那麼則會失效，也能夠參考這裏手動設置無效。

 

[cpp] view plain copy

 

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

若是是由於自定義導航按鈕而致使手勢返回失效，那麼能夠在NavigationController的viewDidLoad函數中添加以下代碼：

 

 

[cpp] view plain copy

 

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. }  

這樣寫了之後就能夠經過手勢滑動返回上一層了，可是若是在push過程當中觸發手勢滑動返回，會致使導航欄崩潰（從日誌中能夠看出）。針對這個問題，咱們須要在pop過程禁用手勢滑動返回功能：

 

 

[cpp] view plain copy

 

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 plain copy

 

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. }  

除了使用系統默認的動畫，還可使用自定義過渡動畫（豐滿的文檔）：

 

 

[cpp] view plain copy

 

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. }  

以下這個代理方法是用來提供一個非交互式的過渡動畫的：

 

 

[cpp] view plain copy

 

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. }  

而下面這個代理方法則是提供交互式動畫：

 

 

[cpp] view plain copy

 

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

這兩個組合起來使用。首先，咱們須要有個動畫：

 

 

[cpp] view plain copy

 

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

 

[cpp] view plain copy

 

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，交互式動畫是經過

[cpp] view plain copy

 

1. UIPercentDrivenInteractiveTransition  

來維護的，在滑動過程當中根據滑動距離來進行更新：

[cpp] view plain copy

 

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];  

當手勢結束時要作出收尾動做：

 

 

[cpp] view plain copy

 

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.     }  

一樣地，自定義的動畫也會有上面提到的導航欄崩潰問題，也能夠經過相似的方法來解決：

 

 

[cpp] view plain copy

 

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.     }  

 

補充：位於當前navgationController的第一個（[0]）viewController時須要設置手勢代理，不響應。