Application Error net::ERR_CONNECTION_REFUSED (http://localhost/)

hello
i create app in ionic4 type=angular
but when i build apk file I got this error message
i need a help

I found this Post, one of these comands will help you

ionic cordova plugin rm cordova-plugin-ionic-webview
ionic cordova plugin add cordova-plugin-ionic-webview@1.2.1
ionic cordova platforms remove android
rm -rf plugins
ionic cordova build android

Have you found a solution ?
I have the same problem, i just update Angular 7 to 8.