Android animated ShapeDrawable
<p>I'm trying to write animated <code>Drawable</code> based on <code>ShapeDrawable</code> class using some specific <code>Shape</code> based class to draw its content.</p>

<p>On demand some values in <code>Shape</code> based class should be changed and it should be changed due to these values (something like temperature change on some scale). Whole thing is written for Android 2.1. I found, that call of <code>invalidateSelf()</code> for my <code>ShapeDrawable</code> should be fine, but I have to provide <code>Drawable.Callback</code> for it.</p>

<p>And question is, what should be provided in <code>invalidateDrawable( Drawable who )</code> method for <code>Drawable.Callback</code> interface? Some samples using such approach:</p>

<pre><code>class MyShapeDrawable extends ShapeDrawable implements Drawable.Callback
{
    public void invalidateDrawable( Drawable who ) {
    }

    public void scheduleDrawable(Drawable who, Runnable what, long when) {
    }

    public void unscheduleDrawable(Drawable who, Runnable what) {
    }
}
</code></pre>

<p>When I call <code>invalidateSelf()</code> for my <code>ShapeDrawable</code> based class <code>invalidateDrawable()</code> method is called, but what should be done in this method? How to force my <code>Shape</code> to be updated and redrawn?</p>
