I have researched this a little before and kept crossing conversations where people were saying that there isn't such an event to capture.
Not sure what you are wanting to capture this event for but, here is a little work around that helped me:
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    final int proposedheight = MeasureSpec.getSize(heightMeasureSpec);
    final int actualHeight = getHeight();
    if (actualHeight > proposedheight){
        // Keyboard is shown
    } else {
        // Keyboard is hidden
    }
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
Source. Let me know if that helps