iOS自己定义返回button(不影响返回手势)

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

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