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

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 5 - (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