添加方法到UINavigationBar后退button？

我如何添加方法到UINavigationbar后退button，所以每当我点击后退button，我需要检查一些值，并显示UIAlertView？ 有没有这个选项？

我尝试了这种方法，但它为我工作

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated { //show alert } 

而且这种方法，但都不是woking

 -(void) viewWillDisappear:(BOOL)animated { if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) { // back button was pressed. We know this is true because self is no longer // in the navigation stack. NSLog(@"hi"); } 

Answer 1

是的，你可以在viedDidLoad

 UIBarButtonItem * backBtn = [[UIBarButtonItem alloc]initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(goBackToAllPets:)]; self.navigationItem.leftBarButtonItem = backBtn; 

写下面的function来检查情况

 -(void)goBackToAllPets:(id)sender { if(/*check condition*/) { UIAlertView *alert = [[UIAlertView alloc]initWithTitle:nil message:@"message" delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil]; alert.tag = 0; [alert show]; } else { [self.navigationController popViewControllerAnimated:YES]; } } 

Answer 2

假设你有两个控制器 – Controller1和Controller2。 Controller2从Controller1被推送。 所以在从Controller1导航控制器上推Controller2之前

 Controller2 *controller2 = [[[Controller2 alloc] init]autorelease]; self.navigationItem.hidesBackButton = YES; 

现在，在Controller2的viewDidLoad：方法中，添加以下片段

 UIBarButtonItem *backBarButtonItem =[[[UIBarButtonItem alloc]initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(goBackToAllPets:)]autorelease]; self.navigationItem.leftBarButtonItem = backBarButtonItem; 

并在backButtonClicked方法中，您可以执行您想要的检查。