how to use showdialog in flutter code example

Example 1: flutter alertdialog

Future<void> _showMyDialog() async {
  return showDialog<void>(
    context: context,
    barrierDismissible: false, // user must tap button!
    builder: (BuildContext context) {
      return AlertDialog(
        title: Text('AlertDialog Title'),
        content: SingleChildScrollView(
          child: ListBody(
            children: <Widget>[
              Text('This is a demo alert dialog.'),
              Text('Would you like to approve of this message?'),
            ],
          ),
        ),
        actions: <Widget>[
          TextButton(
            child: Text('Approve'),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
        ],
      );
    },
  );
}

Example 2: showdialog with builder flutter

showDialog(
        context: context,
        builder: (BuildContext context) => new AlertDialog(
          title: new Text('Warning'),
          content: new Text('Hi this is Flutter Alert Dialog'),
          actions: <Widget>[
            new IconButton(
                icon: new Icon(Icons.close),
                onPressed: () {
                  Navigator.pop(context);
                })
          ],
        ));