iOS7【隐藏导航栏返回键的Title】

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    self.title = @"My Title Can Be hidden";

    self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@""
                                                                             style:UIBarButtonItemStylePlain
                                                                            target:nil
                                                                            action:nil];
}