Flutter onClosing callback for showModalBottomSheet : <p>I have a <code>showModalBottomSheet</code> like the below, which I understand to inherit from <code>BottomSheet</code> (right?)</p>

<pre><code>      showModalBottomSheet&lt;void&gt;(
        context: context,
        builder: (BuildContext context) {
          return Container(
            height: 260.0,
            child: Text('I am text')
          );
        },
      );
</code></pre>

<p>What I want to do:</p>

<p>I want to know (listen) when the modal is being closed, and act on it.</p>

<p>I've seen this <code>onClosing</code> callback: 
<a href="https://docs.flutter.io/flutter/material/BottomSheet/onClosing.html" rel="noreferrer">https://docs.flutter.io/flutter/material/BottomSheet/onClosing.html</a></p>

<p>How can I have a listener attached to the <code>showModalBottomSheet</code>, and then act accordingly when it fires?</p>
