在自定义UINavigationController中，利用系统自带左边缘滑动手势实现全屏幕都可以点击滑动

1.防止手势冲突
   self.interactivePopGestureRecognizer.enabled = NO;
2.给自定义UINavigationController的view添加手势
  让'self.interactivePopGestureRecognizer.delegate'监听滑动事件
  实现系统内部方法(po xx手势)：'handleNavigationTransition:'
   UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] 
                                 initWithTarget:self.interactivePopGestureRecognizer.delegate 
                                 action:@selector(handleNavigationTransition:)];
3.再将自定义手势的代理设置为控制器
   pan.delegate = self;
   [self.view addGestureRecognizer:pan];

实现代理方法，例如：
如果不是第一个控制器就可以滑动
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    // 手势何时有效 : 当导航控制器的子控制器个数 > 1就有效
    return self.childViewControllers.count > 1;
}

解决系统返回手势与scrollView滑动手势冲突问题
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer 
        shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    // 首先判断响应gestureRecognizer的view是不是系统UILayoutContainerView
    if ([gestureRecognizer.view isKindOfClass:NSClassFromString(@"UILayoutContainerView")]) {
        // 如果otherGestureRecognizer的响应者是UIScrollView，
        // 再判断otherGestureRecognizer的state是began，
        // 同时判断scrollView的位置是不是正好在最左边
        // 满足条件即可实现返回手势
        if ([otherGestureRecognizer.view isKindOfClass:[UIScrollView class]]) {
            UIScrollView *scrollView = (UIScrollView *)otherGestureRecognizer.view;
            if (otherGestureRecognizer.state == UIGestureRecognizerStateBegan &&
                scrollView.contentOffset.x == 0) {
                return YES;
            }
        }
    }
    return NO;
}

进入某个页面禁止手势后可以重写系统方法,恢复手势响应
- (NSArray<UIViewController *> *)popToRootViewControllerAnimated:(BOOL)animated
{
    self.interactivePopGestureRecognizer.enabled = YES;
    return  [super popToRootViewControllerAnimated:animated];
}

如何解决导航控制器pop手势失效

成为手势代理
self.interactivePopGestureRecognizer.delegate = self;

实现需要的代理方法(基本同上)，例如：
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    // 手势何时有效 : 当导航控制器的子控制器个数 > 1就有效
    return self.childViewControllers.count > 1;
}