Android detect keyboard

KeyboardDetectorFragment.kt

// Android detect keyboard

abstract class KeyboardDetectorFragment : Fragment() {

    private lateinit var layoutChangeListener: View.OnLayoutChangeListener

    init {
        initLayoutChangeListener()
    }

    override fun onResume() {
        super.onResume()
        addKeyboardDetector()
    }

    override fun onPause() {
        super.onPause()
        removeKeyboardDetector()
    }

    // === Protected methods ===

    protected abstract fun onShowKeyboard()

    protected abstract fun onHideKeyboard()

    // === Private methods ===

    // Show or hide help text and icon on keyboard show or hide.
    private fun initLayoutChangeListener() {
        layoutChangeListener =
            View.OnLayoutChangeListener { v, left, top, right, bottom, oldLeft, oldTop, oldRight, oldBottom ->

                val oldHeight = oldBottom - oldTop
                val height = bottom - top

                // 0.15 ratio is perhaps enough to determine keypad height
                val ratio = 0.15

                if (height < oldHeight && (oldHeight - height) > ratio * oldHeight) {
                    // If new screen is smaller, than before,
                    // then keyboard is shown
                    onShowKeyboard()
                } else if (height > oldHeight && (height - oldHeight) > ratio * height) {
                    // If new screen is bigger, than before,
                    // then keyboard is hidden
                    onHideKeyboard()
                }
            }
    }

    // This will be triggered only if windowSoftInputMode="adjustResize" is set for the activity.
    private fun addKeyboardDetector() =
        getActivityRootView()?.addOnLayoutChangeListener(layoutChangeListener)

    private fun removeKeyboardDetector() =
        getActivityRootView()?.removeOnLayoutChangeListener(layoutChangeListener)

    private fun getActivityRootView() = activity?.findViewById<View>(R.id.main_activity_root_view)
}