Calling popToRootViewControllerAnimated after UIImagePicker finish or cancel? (iPhone, Objective C)

Question

I am trying to implement live camera functionality in my iPhone application and am running into trouble. Basically, the way it is structured is this: I provide a UINavigationController wherein the user can navigate to an image with a table view and (upon choosing one) a detail view.

They can then click on a button and take a new photo with the camera. Ideally, what should happen is that after taking the photo or canceling they go back to the navigation root where the images are listed again. For this, I am implementing the UIImagePickerController delegate within my main detail view controller.

All of that is implemented just fine except that last bit - I can access the photo, etc. but when attempting to return to that first listing - using popToRootViewControllerAnimated - I get an EXC_BAD_ACCESS error. Here is a reduced version of the relevant code (didFinishPickingMediaWithInfo ... imagePickerControllerDidCancel works the same way):

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    // Do some image processing stuff here...

    [picker dismissModalViewControllerAnimated:YES];
    [picker release];

    [self.navigationController popToRootViewControllerAnimated:YES];    
}

Commenting out that last line makes it work, but then it just goes back to the detail view with the original photo, not the listing.

Anyone?

Update: A detail I neglected to mention before... The pop does, in fact, appear to work to a degree. The camera picker is dismissed and it goes back to the listing. However, that's when the app dies (the selected table cell is still blue, from where the user tapped before). I also tried using popViewControllerAnimated instead with the exact same result.

Answer 1

You problem here is [picker dismissModelViewController] and [picker release] i believe ... You do not need to release the picker, it is releasedd for u when u dismiss the modal view controller i believe (which you arent doing correctly from what i can s ee)...Either that or it has a reference count of 0 and should not be release, either way i recall doing something like this and having it crash because i released the picker...Also i noticed you are having the picker dismiss the modal view controller, are you sure this is what you are trying t o do? not [self dismissModalViewController] or which ever ViewController you pushed that view onto?

Answer 2

The answer:
Use this: [self.navigationController dismissModalViewControllerAnimated:YES]; code instead of [picker dismissModalViewControllerAnimated:YES];
Now, you can remove this line from your code: [self.navigationController popToRootViewControllerAnimated:YES];

Answer 3

Hey,

Hope this isn't too late for you. I just ran into the same problem tonight and banged my head against my MBP for about 30min before I started getting a little creative.

I found two ways to make this work. Neither is intuitive, but here you go. Basically, it seems the issue might be caused by the fact that you are calling "pop" on the navigationController before the "dismiss" animation has finished.

I found that if I set the animation boolean on the dismiss to "NO", then it worked.

E.g.

[picker dismissModalViewControllerAnimated:**NO**];

Another option is to create a 2nd method that actually calls the "pop" function, and call it using a timer with a short offset. Just enough for the dismiss animation to run.

E.g.

-(void)popMe {
    [self.navigationController popToRootViewControllerAnimated:YES];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    [picker dismissModalViewControllerAnimated:YES];
    [picker release];

    [self performSelector:@selector(popMe) withObject:nil afterDelay:0.1];   
}

That timing worked for me, you may have to adjust.

Hope that helps!

• Andrew