Flutter Webview scrolling is leggy or not so smooth

Question

Note I have not added complete code.

In below code I am rendering CircularProgressIndicator and InAppWebView at once to avoid the white screen displayed (Apart from splash and launch screen) by the InAppWebView at the time of loading.

I am using opacity to display one widget at a time. In my example initially CircularProgressIndicator is visible only for 5 seconds. Than after those 5 seconds InAppWebView is displayed which was kept invisible.

Using of Stack layout makes webview scroll leggy. I need to figure out on how to render CircularProgressIndicatora and InAppWebView together without having to use stack.

body: WillPopScope(
        onWillPop: onWillPop,
        child: Stack(
          children: <Widget>[
            Opacity(
              opacity: _isLoadingPage ? 1.0 : 0.0,
              child: Center(
                child: CircularProgressIndicator(
                  valueColor: AlwaysStoppedAnimation<Color>(Colors.deepPurple),
                ),
              ),
            ),
            Opacity(
              opacity: _isLoadingPage ? 0.0 : 1.0,
              child: InAppWebView(
                initialUrl: 'https://www.theonlineindia.co.in',             
              ),
            ),
        ],
    ),
),