UIImagePickerController: Detecting Camera button (shutter) pressed

Question

I would like to call a method that takes an NSNotification immediately after the user presses the camera shutter (i.e when the "Preview" tab bar has the buttons "Retake" and "Use").

I can't use the didFinishPickingImage method because at this time the user has already pressed the "Use" button.

I have already implemented this by cameraOverlayView property of UIImagePickerController(see comments), but I wonder whether there are quicker ways of 'observing' this action.

Any ideas?

Infecund

what are you trying to accomplish? could you use custom picture taking controls and bypass the standard use/retake controls? – Tristichous

I want to display an alert after the user takes the picture. I am trying to avoid using Custom Views to raise the chances of the app being accepted in the App Store. – Infecund

As a credit to David who mentioned it, because I was running out of time in my project, this was my way out. So I settled for the cameraOverlay feature of SDK 3.1+ to solve this. Ref: 1. developer.apple.com/iphone/library/documentation/UIKit/… 2. mobile-augmented-reality.blogspot.com/2010/01/…. It is legit so no worries about Apple. But was time consuming than a simple observer method would do. – Infecund

Answer 1

To learn about camera button press event, you can fire a NSNotification for it.

// Add observer for when camera button is pressed
NSNotificationCenter.defaultCenter().addObserver(self, selector: @selector(yourFunctionToPerform), name: "_UIImagePickerControllerUserDidCaptureItem", object: nil)

Also add the following method to the ViewController where you are creating ImagePickerViewController:

-(void) yourFunctionToPerform{

    //Do what you want to do on Camera button tap event

}

I was searching for this problem too, the key/name for the event is really obscure.

Briticism

Thank you so much, you're a genius! Easy and not workarounded solution at all! I definitelly like that approach :) – Ravid

Answer 2

You CAN display it AFTER they choose the image.

- (void)imagePickerController:(UIImagePickerController *)picker 
        didFinishPickingImage:(UIImage *)image
                  editingInfo:(NSDictionary *)editingInfo
{
        //Display the UIAlertView
    [alertView show];
        //Just never use the image
}

If you don't want to use the image you really don't have to

Bouffard

Thanks Jaba. But the idea really is that I want to catch the user while he can still quickly "Retake" the picture. Reason: User friendliness. – Infecund