title: Flutter Checkbox - how to set colour in unchecked state
body: <p>In Flutter a Checkbox appears to be transparent, in its natural unchecked state. I would like to know how to set the colour of the box in this state.</p>
  <p>There are many similar questions here but they all ask to change the active colour, or the colour of the tick. I've tried all of the available properties but none of them seem to affect the unchecked state (not even fillColor). My goal is to create a solid white checkbox (square with rounded corners) which shows up against a non-white background.</p>
  <pre class="lang-dart prettyprint-override"><code>child: Checkbox(
    checkColor: Colors.red,
    activeColor: Colors.white,
    shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(5)),
    onChanged: (value) {},
  ),
  </code></pre>
  <p><a href="https://i.stack.imgur.com/qe2Qg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qe2Qg.png" alt="enter image description here" /></a></p>