While there are many methods posted on SO regarding hacking keyboards to work, for example, How can I support the up and down arrow keys with a Bluetooth keyboard under iOS 7, or Receive iPhone keyboard events, none of them are documented.
Is it possible to detect a keyUp: / keyDown: input event from a hardware keyboard (e.g. bluetooth) in iOS using public APIs?
As of iOS 13.4, this is now possible due to the introduction of UIKey, which is included on pressesBegan events now when a keyboard key is pressed. this guide from Swift By Sundell covers some examples. Here is the relevant bit:
class EditorViewController: UIViewController {
...
override func pressesBegan(_ presses: Set<UIPress>,
with event: UIPressesEvent?) {
super.pressesBegan(presses, with: event)
presses.first?.key.map(keyPressed)
}
override func pressesEnded(_ presses: Set<UIPress>,
with event: UIPressesEvent?) {
super.pressesEnded(presses, with: event)
presses.first?.key.map(keyReleased)
}
override func pressesCancelled(_ presses: Set<UIPress>,
with event: UIPressesEvent?) {
super.pressesCancelled(presses, with: event)
presses.first?.key.map(keyReleased)
}
}
Brace yourself. The answer is- this is not possible.
Yes. It is 2020, 6 years after I initially posted this question, and the answer is still- while iOS internally handles keyup/keydown messages, it is just not legal to intercept them.
What this says for the state of Apple's interest in iOS as a realistic computing environment, I don't know, but until someone posts a better answer, the fact is, you are supposed to accept keyboard handling as a purely input method impulse. Apparently touch won so conclusively, you will never again be able to recreate the ability to detect a sustained keypress. Nice.
