- (void)viewDidLoad
{
    [super viewDidLoad];
 
    if ([[[UIDevice currentDevice] systemVersion] floatValue] < 7.0) {
 
        // 1、修改导航条样式
        UINavigationBar *bar = [UINavigationBar appearance];
        // 修改导航条背景
        [bar setBackgroundImage:[UIImage imageNamed:@"navigationbar_background.png"] forBarMetrics:UIBarMetricsDefault];
        // 修改导航条文字样式
        [bar setTitleTextAttributes:@{
                                      UITextAttributeTextColor : [UIColor blackColor],
                                      UITextAttributeTextShadowOffset : [NSValue valueWithUIOffset:UIOffsetZero]
                                      }];
 
 
        // 2、修改导航条按钮样式
        UIBarButtonItem *item = [UIBarButtonItem appearance];
 
        UIImage *normal = [UIImage imageNamed:@"navigationbar_button_background.png"];
        UIImage *highlight = [UIImage imageNamed:@"navigationbar_button_background_pushed.png"];
 
        // 修改导航条按钮背景
        [item setBackgroundImage:normal forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
        [item setBackgroundImage:highlight forState:UIControlStateHighlighted barMetrics:UIBarMetricsDefault];
 
        // 修改导航条按钮文字样式
        [item setTitleTextAttributes:@{
                                       UITextAttributeTextColor : kBlueColor,
                                       UITextAttributeTextShadowOffset : [NSValue valueWithUIOffset:UIOffsetZero],
                                       } forState:UIControlStateNormal];
        [item setTitleTextAttributes:@{
                                       UITextAttributeTextColor : kBlueColor,
                                       UITextAttributeTextShadowOffset : [NSValue valueWithUIOffset:UIOffsetZero]
                                       } forState:UIControlStateHighlighted];
 
        [item setBackButtonBackgroundImage:normal forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
        [item setBackButtonBackgroundImage:highlight forState:UIControlStateHighlighted barMetrics:UIBarMetricsDefault];
 
        // 3、修改状态栏样式
        [UIApplication sharedApplication].statusBarHidden = NO;
        [UIApplication sharedApplication].statusBarStyle = UIStatusBarStyleBlackOpaque;
 
    }
}
 
#pragma mark - 2、代理方法
#pragma mark 2.1、控制器将要视图显示
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    // 在未自定义导航条返回键的情况下，iOS6及以下版本设备导航条自动添加仿iOS7返回按钮（根控制器例外）
    if (!(viewController == navigationController.viewControllers.firstObject || [(RMBaseVCtrl *)viewController isCustomNBI]) && [viewController isKindOfClass:[RMBaseVCtrl class]]){
 
        // 栈控制器数组
        NSArray *vcs = navigationController.viewControllers;
 
        // 前一个控制器序号
        int penultimate = (int)vcs.count - 2;
 
        if (penultimate >= 0) {
 
            // 前一个控制器标题[......]<p class="read-more"><a href="https://www.yusian.com/blog/project/2014/08/09/232925559.html">继续阅读</a></p>