There may be a simpler way, but in the past I've created a dummy edittext which is off screen or permanently hidden behind something else, with it's inputtype set to None so the keyboard doesn't display.
When I want to hide the focus I'll call a sub something like:
Sub HideFocus
HiddenET.Text="" 'In case a keyboard is attached and something has been typed
HiddenET.RequestFocus
End Sub