getting 'The named parameter '~' isn't defined.' error during adding Flutter AdMob(Banner)

Question

Now I've tried to add AdMob(Banner) to my flutter project.

I add all dependencies to

1. pubspec.yaml(google_mobile_ads: ^2.3.0)
2. Info.plist

<key>GADApplicationIdentifier</key>
    <string>test id</string>

3. AndroidManifest.xml

<meta-data
           android:name="com.google.android.gms.ads.APPLICATION_ID"
           android:value="test id"/>

4. import right package file too.

import 'package:google_mobile_ads/google_mobile_ads.dart';

But as you can see, this error doesn't disappear at all.. I used exactly same code which described in the official document. Not only for the parameters, other method(like load()) cannot find too. https://developers.google.com/admob/flutter/banner/get-started?hl=ko

enter image description here

is anyone there who has same problem? If you have any idea about this error, please let me know how to fix it! I'm spending three days with this error, but did't get a solution yet.

I tried build the project several times. Also close and restart Android Studio, delete dependency and add Again. Also I checked sdk, flutter, Android Studio version too. But still don't know what's the problem and how to fix.