[搬运] iOS 7 侧滑返回手势使用和错误集


 

原文:http://blog.sina.com.cn/s/blog_65c178a80102v0f4.html


前言:
ios7开始 苹果增加了页面 右滑返回的效果;具体的是以UINavigationController为容器的ViewController间右滑切换页面。
代码里的设置是:

self.navigationController.interactivePopGestureRecognizer.enabled = YES;(default is YES)

可以看到苹果给navigationController添加了一个手势(具体为UIScreenEdgePanGestureRecognizer(边缘手势,同样是ios7以后才有的)),就是利用这个手势实现的 ios7的侧滑返回。

问题1:
然而事情并非我们想的那么简单。
1.当我们用系统的UINavigationController,并且也是利用系统的navigateBar的时候,是完全没有问题的
2.但是当我们没有用系统的navigateBar或者自定义了返回按钮的时候,这个时候 右滑返回是失效的。

解决(问题1)办法:
对于这种失效的情况,考虑到interactivePopGestureRecognizer也有delegate属性,替换默认的self.navigationController.interactivePopGestureRecognizer.delegate来配置右滑返回的表现也是可行的。

我们可以在NavigationController中设置一下:
self.navigationController.interactivePopGestureRecognizer.delegate =(id)self

问题2
但是出现很多问题,比如说在rootViewController的时候这个手势也可以响应,导致整个程序页面不响应;push了多层后,快速的触发两次手势,也会错乱

解决(问题2)办法:

@interface NavRootViewController : UINavigationController
@property(nonatomic,weak) UIViewController* currentShowVC;
@end
  
@implementation NavRootViewController
-(id)initWithRootViewController:(UIViewController *)rootViewController
{
NavRootViewController* nvc = [super initWithRootViewController:rootViewController];
self.interactivePopGestureRecognizer.delegate = self;
nvc.delegate = self;
return nvc;
}
 
-(void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
}
-(void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
if (navigationController.viewControllers.count == 1)
self.currentShowVC = Nil;
else
self.currentShowVC = viewController;
}
 
-(BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
if (gestureRecognizer == self.interactivePopGestureRecognizer) {
return (self.currentShowVC == self.topViewController); //the most important
}
return YES;
}
 
@end
借鉴了别人的方法:具体是通过 获取当前pushView栈里的当前显示的VC,根据这个VC来决定 是否开启手势(如果currentShowVC 是当前显示的,则开启手势;如果 currentShowVC为nil,则代表在主页面,关闭手势)
注:
当时试了一种方法 就是滑动的时候来回设置 interactivePopGestureRecognizer的delegate;发现 会有crash,原因就是 因为 我把 当前显示的VC设置为了这个手势的delegate,但当这个VC消失的时候,这个delegate便被释放了,导致crash

至此,觉得ios7上的右滑返回大功告成了,心里正happy,妈蛋,发现了一个可耻的bug:
UIScrollView 上 右滑返回的手势失灵了,靠!!!!!!

问题三:

UIScrollView上手势失灵:
经研究,发现是
UIScrollView上已经添加了 panGestureRecognizer(滑动)手势

技术分享

解决(问题三)办法:
参考:http://www.cnblogs.com/lexingyu/p/3702742.html

【解决方案】

苹果以UIGestureRecognizerDelegate的形式,支持多个UIGestureRecognizer共存。其中的一个方法是:

1 // called when the recognition of one of gestureRecognizer or otherGestureRecognizer would be blocked by the other 
2 // return YES to allow both to recognize simultaneously. the default implementation returns NO (by default no two gestures can be recognized simultaneously) 
3 // 
4 // note: returning YES is guaranteed to allow simultaneous recognition. returning NO is not guaranteed to prevent simultaneous recognition, as the other gesture‘s delegate may return YES 

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;

 一句话总结就是此方法返回YES时,手势事件会一直往下传递,不论当前层次是否对该事件进行响应。

 @implementation UIScrollView (AllowPanGestureEventPass)

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]
        && [otherGestureRecognizer isKindOfClass:[UIScreenEdgePanGestureRecognizer class]])
    {
        return YES;
    }
    else
    {
        return  NO;
    }
}

事实上,对UIGestureRecognizer来说,它们对事件的接收顺序和对事件的响应是可以分开设置的,即存在接收链和响应链。接收链如上文所述,和UIView绑定,由UIView的层次决定接收顺序。

而响应链在apple君的定义下,逻辑出奇的简单,只有一个方法可以设置多个gestureRecognizer的响应关系:

// create a relationship with another gesture recognizer that will prevent this gesture‘s actions from being called until otherGestureRecognizer transitions to UIGestureRecognizerStateFailed // if otherGestureRecognizer transitions to UIGestureRecognizerStateRecognized or UIGestureRecognizerStateBegan then this recognizer will instead transition to UIGestureRecognizerStateFailed // example usage: a single tap may require a double tap to fail - (void)requireGestureRecognizerToFail:(UIGestureRecognizer *)otherGestureRecognizer;

每个UIGesturerecognizer都是一个有限状态机,上述方法会在两个gestureRecognizer间建立一个依托于state的依赖关系,当被依赖的gestureRecognizer.state = failed时,另一个gestureRecognizer才能对手势进行响应。

所以,只需要

[_scrollView.panGestureRecognizer requireGestureRecognizerToFail:screenEdgePanGestureRecognizer];

 - (UIScreenEdgePanGestureRecognizer *)screenEdgePanGestureRecognizer
{
    UIScreenEdgePanGestureRecognizer *screenEdgePanGestureRecognizer = nil;
    if (self.view.gestureRecognizers.count > 0)
    {
        for (UIGestureRecognizer *recognizer in self.view.gestureRecognizers)
        {
            if ([recognizer isKindOfClass:[UIScreenEdgePanGestureRecognizer class]])
            {
                screenEdgePanGestureRecognizer = (UIScreenEdgePanGestureRecognizer *)recognizer;
                break;
            }
        }
    }

    return screenEdgePanGestureRecognizer;
}

参考:

牛逼 解决了iOS7下滑动返回与ScrollView共存
http://www.cnblogs.com/lexingyu/p/3702742.html

更牛逼  解决了interactivePopGestureRecognizer.delegate 的 释放导致crash的问题
http://www.2cto.com/kf/201401/272886.html


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