按下导航控制器的左键按钮时如何停止视图消失

Question

I am rookie to iOS .In my child view controller i made some modification in data. I inserted a done button to store a data and pop the view controller from navigation controller stack. if i press navigation controller back button it automatically goes to back without saving data. if i made any modification in data and then i pressed back button i need show alert as "modifications are made are sure want to go back". if the user press the cancel button in alert view i need to stop view disappearing and still stand on same view controller.If anybody have the answer please help me.

Answer 1

I think this is a way to do it

    - (void)viewDidLoad{
        [super viewDidLoad];
        [self.navigationItem setLeftBarButtonItem:nil];
        [self.navigationItem setHidesBackButton:YES];

    UIButton *myButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 100, 44)];
    [myButton setImage:[UIImage imageNamed:@"back.png"] forState:UIControlStateNormal];
    //back.png = your image name
    [myButton setTitle:@"Back" forState:UIControlStateNormal];
    [myButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [myButton addTarget:self action:@selector(backButtonTapped:) forControlEvents:UIControlEventTouchUpInside];
    UIBarButtonItem *customBackButton = [[UIBarButtonItem alloc] initWithCustomView:myButton];
    [self.navigationItem setLeftBarButtonItem:customBackButton];

    }

    - (void)backButtonTapped:(id)sender{
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Message" message:@"modifications are made are sure want to go back" delegate:self cancelButtonTitle:@"Go Back" otherButtonTitles:@"Stay Here", nil];

        [alert show];
    }

    - (void)alertView:(UIAlertView *)alertView
    clickedButtonAtIndex:(NSInteger)buttonIndex{
        if (buttonIndex == [alertView cancelButtonIndex]){
            [self.navigationController popViewControllerAnimated:YES];
        }else{
            //Stay on the page and do something
        }
    }

Don't forget to add <UIAlertViewDelegate>