How to set rounded border to a MaterialButton on Flutter?

Question

I'm trying set rounded border to my MaterialButton, to do it I'm setting a RoundedRectangleBorder to shape attribute's MaterialButton, the problem is that it's not have effect.

Code:

  Widget _showNeedHelpButton() {
    return new Padding(      
      padding: EdgeInsets.fromLTRB(0.0, 5.0, 0.0, 0.0),
      child: new MaterialButton(
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(20.0))),
        elevation: 5.0,
        minWidth: 200.0,
        height: 35,
        color: Color(0xFF801E48),
        child: new Text('Preciso de ajuda',
            style: new TextStyle(fontSize: 16.0, color: Colors.white)),
        onPressed: () {
          setState(() {
            _isNeedHelp = true;
          });
        },
      ),
    );
  }

Result:

Answer 1

If you need to use MaterialButton() - You need to Warp the button with Material Widget, to get the desired behavior.

    Widget _showNeedHelpButton() {
    return Padding(
      padding: EdgeInsets.fromLTRB(0.0, 5.0, 0.0, 0.0),
      child: Material(  //Wrap with Material
        shape: RoundedRectangleBorder(borderRadius:BorderRadius.circular(22.0) ),
        elevation: 18.0,
        color: Color(0xFF801E48),
        clipBehavior: Clip.antiAlias, // Add This
        child: MaterialButton(
          minWidth: 200.0,
          height: 35,
          color: Color(0xFF801E48),
          child: new Text('Preciso de ajuda',
              style: new TextStyle(fontSize: 16.0, color: Colors.white)),
          onPressed: () {
//          setState(() {
//            _isNeedHelp = true;
//          });
          },
        ),
      ),
    );
  }

Output:

UPDATE:

  minWidth: 200.0,
  height: 95,

Answer 2

MaterialButton(
        child: Text('My Button'),
        height: 40,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(10.0),
        ),
)

RoundedRectangleBorder will help you https://api.flutter.dev/flutter/painting/RoundedRectangleBorder-class.html

Answer 3

You should set the shape for MaterialButton and borderRadius for Material to make it round even when animation tab:

Material(
  elevation: 10.0,
  borderRadius: BorderRadius.circular(30.0),//12
  color: Colors.transparent,//Colors.cyan.withOpacity(0.5),
  child: MaterialButton(
    minWidth: MediaQuery.of(context).size.width,
    color: Colors.cyan.withOpacity(0.7),
    shape: RoundedRectangleBorder(borderRadius:BorderRadius.circular(30.0) ),
    splashColor: Colors.cyan,
    onPressed: () async {},
    child: Text('Login',
        textAlign: TextAlign.center,
        style: TextStyle(
          fontSize: 18.0,
          color: Colors.black,
          fontWeight: FontWeight.w400,
          //fontFamily: lang.font
        )),
  ),
);

Answer 4

Have you tried wrapping it within a ClipRRect() ?

ClipRRect(
  borderRadius: BorderRadius.all(Radius.circular(20.0)),
  child: MaterialButton(...),
),

You can find the documentation here: ClipRRect()