WebView flashes when altering page using Javascript

I have the following code that removes some bloat from my reading app.

```
await handlePreferences().then((s) async {
await _fwp.evalJavascript(pageCleaner).then((s) async {
await _fwp.show();
});
});
```

However, the webview flashes when it's shown, and you can see the bloated page for a second before being replaced. Is there a way to fix this?