a good option is just to close the softkeyboard when there is an input from hardware keyboard
Android classes usually provide event handlers, you can implement when subclassing them. The Activity class has the following event handlers:
- onKeyDown(int keyCode, KeyEvent event)
- onKeyLongPress(int keyCode, KeyEvent event)
- onKeyMultiple(int keyCode, int repeatCount, KeyEvent event)
- onKeyShortcut(int keyCode, KeyEvent event)
- onKeyUp(int keyCode, KeyEvent event)
In addition all views have the following event handlers:
- onKeyDown(int, KeyEvent)
- onKeyUp(int, KeyEvent)
I guess there are many other classes that have similar event handlers for key events, but this should be enough for your situation. The KeyEvent then contains information about the pressed key, i.e. the key code.
in you case you might want to do something like this :
in you activity or view class override on of onKeyDown or onKeyUp methods and 
hide the softkeyboard in there like:
override fun onKeyUp(keyCode: Int, event: KeyEvent?): Boolean {
        hideSoftKeyboard()
        return super.onKeyUp(keyCode, event)
}
or you can add a keyListener for your edittext
mEditText.setOnKeyListener { v, keyCode, event ->
       hideSoftKeyboard()
       return@setOnKeyListener when (keyCode) {
           KeyEvent.ACTION_UP -> {
               hideSoftKeyboard()
               true
           }
           else -> false
       }
}
how to close softKeyword: 
fun hideSoftKeyboard() {
   try {
        val inputMethodManager = getSystemService(
            Activity.INPUT_METHOD_SERVICE
        ) as InputMethodManager
        inputMethodManager.hideSoftInputFromWindow(
            currentFocus!!.windowToken, 0)
    } catch (e: Exception) {}
}