creating service screen that will overlay all other app, but the issue is soft keyboard is not showing

Question

Here's my code

val params = WindowManager.LayoutParams(
        WindowManager.LayoutParams.MATCH_PARENT,
        WindowManager.LayoutParams.MATCH_PARENT,
        WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
        WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE,
    PixelFormat.TRANSLUCENT
    )  

my end goal is to create a overlay that will lessen the overall brightness of the screen.
everything is working, i can tap/access all of the icon from other app.

The issue is, soft keyboard is not showing.

the device I am using is a Asus Zenfone 6 (Android 5.0)