Prompting an UIAlertView to user before navigating back to the previous controller in a UINavigationController stack

Question

I'm trying to prompt a UIAlertView before navigating to the previous controller and preventing navigation if the user decides to stay on the same View Controller. Using CCTBackButtonActionHelper, the UIALertView can be easily generated but the only problem I'm facing is that it changes the color of the back button to gray just like any disabled UIBarButton control when clicked. However, clicking anywhere on the navigation bar restores its original color. So how could i prevent changing its color?

This is how I'm doing it right now.

In CustomNavigationContoller.m

- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {
    BOOL should = [[CCTBackButtonActionHelper sharedInstance] navigationController:self navigationBar:navigationBar shouldPopItem:item];
    if (!should) {
        return NO;
    }
    return [super navigationBar:navigationBar shouldPopItem:item];
}

In CustomViewController.m

#pragma mark - Back button

- (void)cct_navigationBar:(UINavigationBar *)navigationBar willPopItem:(UINavigationItem *)item {
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:nil message:@"Are you sure you want to go back?" delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil];
    [alertView show];
}

#pragma mark - Alert view delegate

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (alertView.cancelButtonIndex == buttonIndex) {
        return;
    }
    [self.navigationController popViewControllerAnimated:YES];
}

Override the popViewController method in UINavigationController and present alert view yourself and pop based on the same. — Sandeep, Jan 27 '15 at 10:30
Possible duplicate of [Confirm back button on UINavigationController](http://stackoverflow.com/questions/8564924/confirm-back-button-on-uinavigationcontroller) — TalkLittle, Oct 09 '15 at 00:08

score 1 · Answer 1 · answered Apr 03 '15 at 22:40

There's a very simple solution.

I'd rather have Apple fix the problem, but your issue (and mine) can be solved by inserting the following in navigationBar:shouldPopItem:

        auto item = navigationBar.topItem;
        item.hidesBackButton = YES;
        item.hidesBackButton = NO;

Saket Kumar · Answer 2 · 2015-01-27T13:30:27.093

0

    you can set condition in viewWillAppear :(BOOL)animated ,
    you can also use method 
    -(void )navigationController :(UINavigationController *)navigationController willshowViewController:(UIViewController *)ViewController animated :(Bool)animated 

    for setting the condition while transitioning to other view controller .


-(void)viewDidLoad{
    [_Back setBackgroundImage:[MyViewController imageFromColor:[UIColor redColor]]  forState:UIControlStateHighlighted];
   
    [_Back setBackgroundImage:[MyViewController imageFromColor:[UIColor blueColor]]  forState:UIControlStateNormal];
   // [_Back setTintColor:[UIColor brownColor]];
}

+ (UIImage *)imageFromColor:(UIColor *)color {
    CGRect rect = CGRectMake(0, 0, 1, 1);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

Hi i am trying this ,and i am able to change the color of back button when i click on it .
Though when i downloaded CCTBackButtonAction and running on xcode 6.1 beta , everything is fine without problem

edited Jan 27 '15 at 13:30

answered Jan 27 '15 at 10:34

Saket Kumar

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What I have to do is to prevent the changing of back button color, else everything is working fine. – Amol Prakash Jan 27 '15 at 11:18
can i generate the same situation you are facing with CCTBackButtonActionHelper ? – Saket Kumar Jan 27 '15 at 12:15
Yes, try to implement. – Amol Prakash Jan 27 '15 at 12:37
In my case, I'm running it on Xcode 6.1.1 and the color of the chevron (arrow part) of back button changes when the UIAlertView Appears. – Amol Prakash Jan 27 '15 at 14:39
Hi i need to post a screen shot to ensure that what am i seeing is different than what u are seeing , as i dont have reputation here i cant post images, so , can you gimme ur email id , so that u can verify it . – Saket Kumar Jan 27 '15 at 15:08
Ok i used custom button in place of default back button of Navigation Controller. It works now. – Amol Prakash Jan 27 '15 at 15:30

score 0 · Accepted Answer · answered Jan 27 '15 at 16:02

I have a simple solution, that has worked perfectly for me without using any third-party component.

#pragma mark - Configuration -

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    self.navigationItem.titleView = self.titleView;
    self.navigationController.navigationBarHidden = NO;
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"red_cross"] style:UIBarButtonItemStyleBordered
                                                                            target:self action:@selector(confirmPopViewController:)];
}

Setup your viewController to use your own navigationItem with a selector.

#pragma mark - Events -

- (void)confirmPopViewController:(id)sender
{
    [[[UIAlertView alloc] initWithTitle:@"My ViewController" message:@"Do you really want to close ?" delegate:self cancelButtonTitle:@"cancel" otherButtonTitles:@"Yes", nil] show];
}

Implement the event and create/show a your UIAlertView There.

#pragma mark - Delegates -
#pragma mark UIAlertViewDelegate

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    if (buttonIndex)
        [self.navigationController popViewControllerAnimated:YES];
}

Finally, with the UIAlertViewDelegate, check if the choice of your user and respond accordingly.

Here when the user confirm we popViewControllerAnimated or we do nothing.

Yes it can be done like this, but i was trying not to change the default back button of UINavigationController. — Amol Prakash, Jan 27 '15 at 16:48
You were trying not to change the instance of the back button or only the looks ? I guess you don't want to repeat the code on every controller, is that right ? — Lifely, Jan 28 '15 at 14:29

Prompting an UIAlertView to user before navigating back to the previous controller in a UINavigationController stack

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