How to show Loading Indicator in WebView Flutter?

Full Example

class WebViewState extends State<WebViewScreen>{

  String title,url;
  bool isLoading=true;
  final _key = UniqueKey();
  
  WebViewState(String title,String url){
    this.title=title;
    this.url=url;
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
          title: Text(this.title,style: TextStyle(fontWeight: FontWeight.w700)),centerTitle: true
      ),
      body: Stack(
        children: <Widget>[
          WebView(
            key: _key,
            initialUrl: this.url,
            javascriptMode: JavascriptMode.unrestricted,
            onPageFinished: (finish) {
              setState(() {
                isLoading = false;
              });
            },
          ),
          isLoading ? Center( child: CircularProgressIndicator(),)
                    : Stack(),
        ],
      ),
    );
  }

}

I just use Stack widget so on top of webview set loading indicator. When callonPageFinished of webview I set isLoading=false variable value and set transparent container.

Complete Example

To Access WebView after complete Loading

class WebViewState extends State<WebViewScreen>{

  String title,url;
  bool isLoading=true;
  final _key = UniqueKey();

  WebViewState(String title,String url){
    this.title=title;
    this.url=url;
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
          title: Text(this.title,style: TextStyle(fontWeight: FontWeight.w700)),centerTitle: true
      ),
      body: Stack(
        children: <Widget>[
          WebView(
            key: _key,
            initialUrl: this.url,
            javascriptMode: JavascriptMode.unrestricted,
            onPageFinished: (finish) {
              setState(() {
                isLoading = false;
              });
            },
          ),
          isLoading ? Center( child: CircularProgressIndicator(),)
                    : Stack(),
        ],
      ),
    );
  }

}