UIImagePickerController：检测相机按钮（快门）被按下

Question

I would like to call a method that takes an NSNotification immediately after the user presses the camera shutter (ie 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?

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.

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