此方法能够自己定义返回button，且不影响返回手势。

新方法：

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]                                         initWithImage:img                                         style:UIBarButtonItemStylePlain                                         target:self                                         action:@selector(onBack:)];self.navigationController.interactivePopGestureRecognizer.delegate = (id
     
      )self;
     

老方法：

UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:self action:nil];    self.navigationController.navigationBar.topItem.backBarButtonItem = backButton;