richtext.dart

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('RichText Widget Demo'),
      ),
      body: Center(
        child: ListView(
          padding: const EdgeInsets.all(20.0),
          children: <Widget>[
            RichText(
              text: TextSpan(
                style: Theme.of(context).textTheme.body1.copyWith(fontSize: 30),
                children: <TextSpan>[
                  TextSpan(
                    text: 'text black withOpacity 0.6\n',
                    style: TextStyle(
                        color: Colors.black.withOpacity(0.6)
                    ),
                  ),
                  TextSpan(
                    text: 'text yellow and green, size 20\n',
                    style: TextStyle(
                        color: Colors.yellow,
                        backgroundColor: Colors.green,
                        fontSize: 20
                    ),
                  ),
                  TextSpan(
                    text: 'text ',
                    style: TextStyle(color: Colors.black.withOpacity(1.0)),
                  ),
                  TextSpan( 
                    text: 'span ',
                    style: TextStyle(color: Colors.red),
                  ),
                  TextSpan(
                    text: 'style ',
                    style: TextStyle(
                        color: Colors.black,
                        fontWeight: FontWeight.bold
                    )
                  ),
                  TextSpan(
                    text: 'get to link',
                    style: TextStyle(
                        color: Colors.blueAccent, fontStyle: FontStyle.italic,
                        decoration: TextDecoration.underline
                    ),
                  )
                ]
              ),
            ),
          ],
        ),
      ),
    );
  }
}

Thanks!