title: flutter change border color on focus
body: <p>what is the easy way to change border color on focus?
  on focus, I want</p>
  <p>in border: Border.all(width: 2, color: Colors.white)),
  child: Icon(...</p>
  <p>to be
  Colors.yellow</p>
  <pre><code>MaterialButton(
      padding: EdgeInsets.all(4.0),
      focusColor: Colors.indigo,
      elevation: 0.0,
      //focusNode: myFocusNode,
      child: Container(
        child: new Align(
            alignment: Alignment.bottomRight,
            child: Container(
              margin: EdgeInsets.all(20),
              padding: EdgeInsets.all(10),
              decoration: BoxDecoration(
                  borderRadius: BorderRadius.circular(50),
                  border: Border.all(width: 2, color: Colors.white)),
              child: Icon(
                Icons.search,
                color: Colors.white,
              ),
            )),
      ),
      onPressed: () async {},
    )
  </code></pre>