How can I make the navigation bar visible only when the soft keyboard is open?

I have an app that should be full screen most of the time. However, I want users to be able to easily go back when using the keyboard. How can I make the navigation bar visible only when the keyboard is open? When the keyboard is turned off, the navigation bar should disappear again.

I added this library to my project. So I was able to type what to do when the keyboard is open:

implementation 'com.github.ravindu1024:android-keyboardlistener:1.0.0'

Then I created two values, one to show and one to hide:

private int showSystemBars() {
    return SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN  |
            SYSTEM_UI_FLAG_LAYOUT_STABLE;
}

private int hideSystemBars() {
    return SYSTEM_UI_FLAG_LAYOUT_STABLE
            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
}

Then I used the library I added:

KeyboardUtils.addKeyboardToggleListener(this, isVisible -> {
        if (isVisible) {
            Toast.makeText(context, "Visible", Toast.LENGTH_SHORT).show();
            getWindow().getDecorView().setSystemUiVisibility(showSystemBars());
        }else {
            Toast.makeText(context, "Invisible", Toast.LENGTH_SHORT).show();
            getWindow().getDecorView().setSystemUiVisibility(hideSystemBars());
        }
    });