Cannot open web app

[HelenMMiao]

Hi, when I am testing flutter_gherkin + flutter_driver, automation cannot open the web app, by 'final driver = await FlutterDriver.connect();'
A blank web page opens and indicating controlled by automation, but cannot open the web app. I guess it has some problem trying to get VMService message. But Know little here. Need help.
BTW, 'final driver = await FlutterDriver.connect();' works well if using flutter_driver only