iPad: Detecting External Keyboard
- by StuartW
My app uses a UIAccessoryView to provide additional keyboard functionality (such as forward/backward tabs and arrows keys) for the virtual keyboard, but that causes UIKeyboardDidShowNotification to fire even when a physical keyboard is present (the accessory appears at the bottom of the screen).
I'd like to check if a physical keyboard is attached when handling UIKeyboardWillShowNotification, to prevent the accessory view from appearing and to prevent my custom view from scrolling up (to make room for the non-existent virtual keyboard).
I've tried examining the UIKeyboardFrameEndUserInfoKey key, but it returns a real size for the virtual keyboard, in spite of nothing being displayed.
Is there any way to detect the presence of a physical keyboard to prevent this unwanted behaviour?
Hmm, the plot thickens.
I tried disabling the input accessory by returning nil from the inputAccessoryView property of the Responder object which triggers the keyboard. That suppresses UIKeyboardWillShowNotification and UIKeyboardDidShowNotification when there is a physical keyboard present, but keeps these notifications when there is no such keyboard. All good so far.
Then I tried re-enabling inputAccessoryView only after UIKeyboardWillShowNotification had been received. This only fires when a virtual keyboard is needed, so it should allow me to reintroduce the accessory view in those circumstances. Or so I thought.
Unfortunately, it seems the OS doesn't check inputAccessoryView after UIKeyboardWillShowNotification, so it fails to show the accessory view when it is needed :o(
That leaves me with two options:
Include the input accessory view, giving extra functionality for virtual keyboard users, but lose the ability to detect a physical keyboard and hence not supporting physical devices; or
Exclude the input accessory altogether, preventing most users from accessing the extra keys, but allowing the app to work with a physical keyboard.
Not a great choice, so I'm still keen to see if anyone else has addressed this problem!
