hideKeyboardOnFocusChange

/*
Make the parent view(content view of your activity) clickable and focusable by adding the following attributes

    android:clickable="true"
    android:focusableInTouchMode="true"
*/

class MyClass {
    private var editText: View

    init {
        editText = findViewById(R.id.editText)
    }

    editText.onFocusChangeListener = View.OnFocusChangeListener
    {
        v, hasFocus ->
        if (!hasFocus) {
            hideKeyboard(v)
        }
    }

//    Функцию hideKeyboard() можно вынести в Util класс
    private fun hideKeyboard(view: View) {
        val inputMethodManager = getSystemService(Activity.INPUT_METHOD_SERVICE) as InputMethodManager
        inputMethodManager.hideSoftInputFromWindow(view.windowToken, 0)
    }
}