iOS 导航栏自带页面右滑pop使用

iOS7之后苹果导航控制器增加了一个左侧边缘右滑pop的手势，在非栈底的控制器里面，从左边右滑之后相当于出栈（pop）样子。

以下设置均在自定义的UINavigationController里操作

// 默认是YES 设置为NO左侧右滑手势就不可用了
self.interactivePopGestureRecognizer.enabled = YES;

也可以通过手势实现右滑
遵守UIGestureRecognizerDelegate协议，设置代理对象，实现一下代理方法即可：
-(void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    self.navigationController.interactivePopGestureRecognizer.delegate = self;
}
#pragma mark - UIGestureRecognizerDelegate
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    if (self.viewControllers.count <= 1) {
        return NO;
    }
    return YES;
}

从网络上找了一个大牛的图谱，感觉介绍的很到位 往下的内容理解了这张图就舒坦了：
[图片上传失败...(image-eefd1c-1512661675098)] )
个人的记忆方法：
backBarButtonItem设置下一个页面的返回按钮
leftBarButtonItem设置当前页面的返回按钮

项目中我们多数会自定义左侧返回按钮leftBarButtonItem，这个时候就算设置self.interactivePopGestureRecognizer.enabled = YES了或者实现手势的代理，左边缘的右滑动手势依旧会失效，例如如下代码写过之后，可以验证一下，失效了。
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (self.viewControllers.count > 0) {
        /* 不是栈底控制器的时候隐藏tabbar */
        viewController.hidesBottomBarWhenPushed = YES;
        // 设置左边的返回按钮leftBarButtonItem
        UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
        backBtn.frame = CGRectMake(0, 0, 44, 44);
        backBtn.imageView.contentMode = UIViewContentModeCenter;
        backBtn.contentEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 34);
        [backBtn setImage:[UIImage imageNamed:@"rrrr"] forState:UIControlStateNormal];
        [backBtn setImage:[UIImage imageNamed:@"rrrr"] forState:UIControlStateHighlighted];
        [backBtn addTarget: self action: @selector(back) forControlEvents: UIControlEventTouchUpInside];
        UIBarButtonItem *backBtnItem=[[UIBarButtonItem alloc]initWithCustomView:backBtn];
        viewController.navigationItem.leftBarButtonItem = backBtnItem;
// 此处改为设置backBarButtonItem 右滑手势可以用，但自定义按钮不展示！！
    }
    [super pushViewController:viewController animated:animated];
}

按照如下方式设置backBarButtonItem或leftBarButtonItem，其他不做任何设置，右滑效果可用：
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (self.viewControllers.count > 0) {
        /* 不是栈底控制器的时候隐藏tabbar */
        viewController.hidesBottomBarWhenPushed = YES;
    }
    [self.navigationBar setBackIndicatorImage:[UIImage imageNamed:@"rrrr"]];
    [self.navigationBar setBackIndicatorTransitionMaskImage:[UIImage imageNamed:@"rrrr"]];
    UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];
    self.navigationItem.backBarButtonItem = backItem;
    [super pushViewController:viewController animated:animated];
}
或者
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (self.viewControllers.count > 0) {
        /* 不是栈底控制器的时候隐藏tabbar */
        viewController.hidesBottomBarWhenPushed = YES;
        [self.navigationBar setBackIndicatorImage:[UIImage imageNamed:@"rrrr"]];
        [self.navigationBar setBackIndicatorTransitionMaskImage:[UIImage imageNamed:@"rrrr"]];
        UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];
        self.navigationItem.leftBarButtonItem = backItem;
    }
    [super pushViewController:viewController animated:animated];
}

进过上面的反复测试：在自定义导航栏控制器中backBarButtonItem不能用View视图方法自定义，而leftBarButtonItem可以。
setBackIndicatorImage和setBackIndicatorTransitionMaskImage无论怎么设置都是只能看到setBackIndicatorImage的图片，找不到原因！！！

然后尝试直接在root视图控制器里面设置返回按钮backBarButtonItem的自定义view,右滑手势可用，但是设置leftBarButtonItem就不能使用右滑手势：
- (void)viewDidLoad {
    [super viewDidLoad];
    // 设置左边的返回按钮
    UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    backBtn.frame = CGRectMake(0, 0, 44, 44);
    backBtn.imageView.contentMode = UIViewContentModeCenter;
    backBtn.contentEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 34);
    [backBtn setImage:[UIImage imageNamed:@"rrrr"] forState:UIControlStateNormal];
    [backBtn setImage:[UIImage imageNamed:@"rrrr"] forState:UIControlStateHighlighted];
    [backBtn addTarget: self action: @selector(back) forControlEvents: UIControlEventTouchUpInside];
    backBtn.backgroundColor = [UIColor redColor];
    
    [self.navigationController.navigationBar setBackIndicatorImage:[UIImage imageNamed:@"rrrr"]];
    [self.navigationController.navigationBar setBackIndicatorTransitionMaskImage:[UIImage imageNamed:@"rrrr"]];
    UIBarButtonItem *backBtnItem=[[UIBarButtonItem alloc]initWithCustomView:backBtn];
    backBtnItem.title = @"";
    self.navigationItem.backBarButtonItem = backBtnItem;
    }

以上是自己的验证，留有很多疑问，期待探讨解决。