Callback routine in Android
<p>I ran into a piece of Android code. I don't quite understand the purpose of the callback because it's empty. </p>

<p>In Animation.java</p>

<pre><code>private AnimationCallback callback = null;

public Animation(final AnimationCallback animationCallBack) {
    this();
    callback = animationCallBack;
}

public void stop() {
    if (callback != null) {
        callback.onAnimationFinished(this);
    }
    active = false;
}
public interface AnimationCallback { void onAnimationFinished(final Animation animation); }
</code></pre>

<p>but in <code>AnimationCallback</code> there's only</p>

<pre><code>public interface AnimationCallback {
    void onAnimationFinished(final Animation animation);
}
</code></pre>

<p>I guess my question is what does <code>callback.onAnimationFinished(this)</code> do? There doesn't seem to have anything inside the routine.</p>
