- (void)viewDidAppear:(BOOL)animated {
self.navigationController.interactivePopGestureRecognizer.delegate = (id)self;//重新设置代理
self.navigationController.interactivePopGestureRecognizer.enabled = NO;//本页面不能右滑
}

UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
backBtn.frame = CGRectMake(5, 2, 21, 35);
[backBtn setImage:[UIImage imageNamed:@"back"] forState:UIControlStateNormal];
[[backBtn rac_signalForControlEvents:UIControlEventTouchUpInside] subscribeNext:^(id x) {
[self.navigationController popViewControllerAnimated:YES];
}];
UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithCustomView:backBtn];
self.navigationItem.leftBarButtonItem = backItem;
self.navigationController.interactivePopGestureRecognizer.enabled = YES;//最重要的一步

UIImage* image = [UIImage imageNamed:@"back"];
UIBarButtonItem *item = [[UIBarButtonItem alloc] init];
[item setBackButtonBackgroundImage:[image resizableImageWithCapInsets:UIEdgeInsetsMake(0, image.size.width, 0, 0)] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
[item setBackButtonTitlePositionAdjustment:UIOffsetMake(-400.f, 0) forBarMetrics:UIBarMetricsDefault];
self.navigationItem.backBarButtonItem = item;
self.navigationItem.backBarButtonItem = item;