Flutter 跳出視窗 showDialog

RaisedButton(
 color: mainColor[300],
 textColor: Colors.white,
 child: Text('提領',
 style: TextStyle(color: Colors.white, fontSize: 17)),
 onPressed: () {
  _showAlertDialog(context);
 },
),

Future<void> _showAlertDialog(BuildContext context) {
  return showDialog<void>(
    context: context,
    builder: (BuildContext context) {
      return AlertDialog(
        title: Text('提領'),
        content: Container(
          height: 70 * StorageUtil.getDouble("textScaleFactor"),
          child: Column(
            children: [
              Text('總金額：'+'9999', style: TextStyle(color: Colors.black)),
              Text('提領金額：'+'9999', style: TextStyle(color: Colors.black)),
              Text('金額結餘：'+'9999', style: TextStyle(color: Colors.black)),
            ],
          ),
        ),
        actions: <Widget>[
          FlatButton(
            color: mainColor[200],
            child: Text('取消', style: TextStyle(color: Colors.white)),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
          FlatButton(
            color: mainColor[500],
            child: Text('確定'),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
        ],
      );
    },
  );
}