You need to define your exact requirement here - what is that you want adjusting focus observer for? As the name suggests, it is a way to signal you that AVCaptureDevice
(reference to "real" device - one of these devices) is adjusting its focus. UIImagePicker
is nothing but a file open dialog, not a real device. It works on top of either camera or static list of image files. While in camera mode, you can observe adjustingFocus.
In case that is your requirement, here is nearest you can refer to.
Refer to UIImagePickerController documentation to define how you can implement this for your own needs.