设置全局push返回按钮样式

/**
 * 可以在这个方法中拦截所有push进来的控制器
 */
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (self.childViewControllers.count > 0) { // 如果push进来的不是第一个控制器
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        [button setTitle:@"返回" forState:UIControlStateNormal];
        [button setImage:[UIImage imageNamed:@"navigationButtonReturn"] forState:UIControlStateNormal];
        [button setImage:[UIImage imageNamed:@"navigationButtonReturnClick"] forState:UIControlStateHighlighted];
        button.size = CGSizeMake(70, 30);
        // 让按钮内部的所有内容左对齐
        button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
//        [button sizeToFit];
        // 让按钮的内容往左边偏移10
        button.contentEdgeInsets = UIEdgeInsetsMake(0, -10, 0, 0);
        [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [button setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
        [button addTarget:self action:@selector(popViewControllerAnimated:) forControlEvents:UIControlEventTouchUpInside];

        // 修改导航栏左边的item
        viewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:button];

        // 隐藏tabbar
        viewController.hidesBottomBarWhenPushed = YES;
    }

    // 这句super的push要放在后面, 让viewController可以覆盖上面设置的leftBarButtonItem
    // 意思是，我们任然可以重新在push控制器的viewDidLoad方法中设置导航栏的leftBarButtonItem，如果设置了就会覆盖在push方法中设置的“返回”按钮，因为 [super push....]会加载push的控制器执行viewDidLoad方法。
    [super pushViewController:viewController animated:animated];
}