At a WWDC24 consultation with the keyboards and input team, I was referred to the UITextInputContext class for detecting hardware keyboard status. However, it's not obvious how this class is intended to be used.
I would like to receive notifications when the UITextInputContext state changes, however, I see no way to accomplish this. I've tried using KVO to observe state changes of the current property of UITextInputContext.class or the hardwareKeyboardInputExpected property of UITextInputContext.current, but receive no change notifications when a USB hardware keyboard is attached/detached, and hit an assertion when trying to stop observing, indicating that the observer is not registered. So I don't think KVO works.
I am interested in knowing whether a hardware keyboard is attached when the virtual onscreen keyboard is hidden or shown (which occurs when the hardware keyboard is attached/detached), so that I may adjust the state of my inputAccessoryView accordingly (it should be hidden when a hardware keyboard is attached).
I've had some success checking the state of UITextInputContext.current.hardwareKeyboardInputExpected during keyboard willHide/willShow notifications (or in a block executed via dispatch_async()), however, it seems that the property value does not change until the first key press after attaching a hardware keyboard, or after the first virtual onscreen key press after detaching a hardware keyboard. The latter is problematic because there are no more keyboard hide/show notifications in which to perform the needed update to my inputAccessoryView UI after the UITextInputContext state change occurs following hardware keyboard disconnection.
Perhaps it's meant that I should monitor key press events and check the status there instead?