Answer
Call Invalidate() on the GraphicsView to request that Draw runs again. Do this whenever the data your drawable depends on changes. For animation, invalidate on a timer or from an animation callback, keeping the Draw method fast to sustain frame rate.
graphicsView.Drawable = _drawable;
_drawable.Progress = 0.75f;
graphicsView.Invalidate(); // schedules a repaintReal-world example A progress gauge repaints smoothly by updating its value and calling Invalidate as a download advances.