自定义NavigationController

@interface BJNavigationController ()<UIGestureRecognizerDelegate>

@end

@implementation BJNavigationController

+ (void)initialize
{
    [self.navigationBar setBackgroundImage:[UIImage imageNamed:@"navigationbarBackgroundWhite"] forBarMetrics:UIBarMetricsDefault];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // 设置导航控制器为手势识别器的代理
    self.interactivePopGestureRecognizer.delegate = self;
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

/**
 *  重写push方法的目的 : 拦截所有push进来的子控制器
 *
 *  @param viewController 刚刚push进来的子控制器
 */
- (void)pushViewController:(UIViewController *)viewController
                  animated:(BOOL)animated
{
    // 如果viewController不是最早push进来的子控制器
    if (self.childViewControllers.count > 0) {
        viewController.navigationItem.leftBarButtonItem = [self backBarBtnItem];
        // 隐藏底部的工具条
        viewController.hidesBottomBarWhenPushed = YES;
    }
    // 所有设置搞定后, 再push控制器
    [super pushViewController:viewController animated:animated];
}

- (UIBarButtonItem *)backBarBtnItem
{
    UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    [backBtn setTitle:@"返回" forState:UIControlStateNormal];
    [backBtn setImage:[UIImage imageNamed:@"nav_backBarBtn"] forState:UIControlStateNormal];
    [backBtn setImage:[UIImage imageNamed:@"nav_backBarBtnHL"] forState:UIControlStateHighlighted];
    [backBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [backBtn setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
    [backBtn sizeToFit];
    // 这句代码放在sizeToFit后面
    backBtn.contentEdgeInsets = UIEdgeInsetsMake(0, -20, 0, 0);
    [backBtn addTarget:self action:@selector(back) forControlEvents:UIControlEventTouchUpInside];
    return [[UIBarButtonItem alloc] initWithCustomView:backBtn];
}

- (void)back
{
    [self popViewControllerAnimated:YES];
}

#pragma mark - <UIGestureRecognizerDelegate>
/**
 *  手势识别器对象会调用这个代理方法来决定手势是否有效
 *
 *  @return YES : 手势有效, NO : 手势无效
 */
- (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;
}

@end