WatchUi.Bitmap's setting is disappered.

I implemented watch face with clock time and picture however coordinates of locX and locY are disappered onUpdate().

Could you tell me how to hold locX and locY onUpdate()?

my source code is below.

in Initialize()

function initialize() {
     WatchFace.initialize();
     myBitmap = new WatchUi.Bitmap({
         :rezId => Rez.Drawables.myBitMap,
        :locX => -30,
        :locY => 0
     });
}

then, onUpdate

function onUpdate(dc as Dc) as Void {
     // Get and show the current time
     var clockTime = System.getClockTime();
     var timeString = Lang.format("$1$:$2$:$3$", [clockTime.hour, clockTime.min.format("%02d"), clockTime.sec.format("%02d")]);
     var view = View.findDrawableById("TimeLabel") as Text;
     view.setText(timeString);
     myBitmap.draw(dc);

     // Call the parent onUpdate function to redraw the layout
     View.onUpdate(dc);
}