如何在 WebView Flutter 中显示加载指示器

我想在屏幕上显示web视图数据之前先显示加载.你怎么能做到？

这是我的代码:

class WebDetailPage extends StatelessWidget {
  final String title;
  final String webUrl;

  final Completer<WebViewController> _controller =
      Completer<WebViewController>();

  WebDetailPage({
    @required this.title,
    @required this.webUrl,
  });

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colour.white,
        title: Text(title, style: TextStyle(color: Colour.midnightBlue)),
        leading: IconButton(
            icon: Icon(Icons.arrow_back, color: Colour.midnightBlue),
            onPressed: () => Navigator.of(context).pop()),
      ),
      body: Center(
        child: WebView(
          initialUrl: webUrl,
          javascriptMode: JavascriptMode.unrestricted,
          onWebViewCreated: (WebViewController webViewController) {
            _controller.complete(webViewController);
          },
        ),
      )
    );
  }
}

有人能帮我解决这个问题吗？因为我已经对它进行了搜索和研究，仍然可以找到解决方案.