App ID problems with firebase_admob 0.6.1 for flutter

I've created a new android app in admob, I've got the id, and I tried using it in the example on the firebase_admob page.

I've added the latest version in a default flutter project and I copied and pasted the code on the page. I only modified the id, I've tried single quotes, I've tried double quotes, with no avail, I've got the same error in the console.

What do I do wrong? I really don't get it, I've spend all day trying to figgure this out. Please help me.

getGoogleAppId failed with exception: java.lang.IllegalStateException: Initialize must be called before getGoogleAppId.: com.google.android.gms.measurement.AppMeasurement.getGmpAppId(Unknown Source:0)

I also get the error

GoogleService failed to initialize, status: 10, Missing google app id value from from string resources with name google_app_id.

and

Missing google_app_id. Firebase Analytics disabled. See ...

This is the code:

import 'package:flutter/material.dart';
import 'package:firebase_admob/firebase_admob.dart';

// You can also test with your own ad unit IDs by registering your device as     a
// test device. Check the logs for your device's ID value.
const String testDevice = 'YOUR_DEVICE_ID';

class MyApp extends StatefulWidget {
@override
_MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {

static final MobileAdTargetingInfo targetingInfo = new MobileAdTargetingInfo(
testDevices: testDevice != null ? <String>[testDevice] : null,
keywords: <String>['foo', 'bar'],
contentUrl: 'http://foo.com/bar.html',
birthday: new DateTime.now(),
childDirected: true,
gender: MobileAdGender.male,
nonPersonalizedAds: true,
);

BannerAd _bannerAd;
InterstitialAd _interstitialAd;

int _coins = 0;

BannerAd createBannerAd() {
return new BannerAd(
adUnitId: BannerAd.testAdUnitId,
size: AdSize.banner,
targetingInfo: targetingInfo,
listener: (MobileAdEvent event) {
print("BannerAd event $event");
},
);
}

InterstitialAd createInterstitialAd() {
return new InterstitialAd(
  adUnitId: InterstitialAd.testAdUnitId,
  targetingInfo: targetingInfo,
  listener: (MobileAdEvent event) {
    print("InterstitialAd event $event");
  },
);
}

@override
void initState() {
super.initState();
FirebaseAdMob.instance
    .initialize(appId: 'ca-app-pub-0463943530925483~4865006927');
_bannerAd = createBannerAd()..load();
RewardedVideoAd.instance.listener =
    (RewardedVideoAdEvent event, {String rewardType, int rewardAmount}) {
  print("RewardedVideoAd event $event");
  if (event == RewardedVideoAdEvent.rewarded) {
    setState(() {
      _coins += rewardAmount;
    });
  }
};
}

@override
void dispose() {
_bannerAd?.dispose();
_interstitialAd?.dispose();
super.dispose();
}


@override
Widget build(BuildContext context) {
return new MaterialApp(
  home: new Scaffold(
    appBar: new AppBar(
      title: const Text('AdMob Plugin example app'),
    ),
    body: new SingleChildScrollView(
      child: new Center(
        child: new Column(
          crossAxisAlignment: CrossAxisAlignment.center,
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            new RaisedButton(
                child: const Text('SHOW BANNER'),
                onPressed: () {
                  _bannerAd ??= createBannerAd();
                  _bannerAd
                    ..load()
                    ..show();
                }),
            new RaisedButton(
                child: const Text('REMOVE BANNER'),
                onPressed: () {
                  _bannerAd?.dispose();
                  _bannerAd = null;
                }),
            new RaisedButton(
              child: const Text('LOAD INTERSTITIAL'),
              onPressed: () {
                _interstitialAd?.dispose();
                _interstitialAd = createInterstitialAd()..load();
              },
            ),
            new RaisedButton(
              child: const Text('SHOW INTERSTITIAL'),
              onPressed: () {
                _interstitialAd?.show();
              },
            ),
            new RaisedButton(
              child: const Text('LOAD REWARDED VIDEO'),
              onPressed: () {
                RewardedVideoAd.instance.load(
                    adUnitId: RewardedVideoAd.testAdUnitId,
                    targetingInfo: targetingInfo);
              },
            ),
            new RaisedButton(
              child: const Text('SHOW REWARDED VIDEO'),
              onPressed: () {
                RewardedVideoAd.instance.show();
              },
            ),
            new Text("You have $_coins coins."),
          ].map((Widget button) {
            return new Padding(
              padding: const EdgeInsets.symmetric(vertical: 16.0),
              child: button,
            );
          }).toList(),
        ),
      ),
    ),
  ),
);
}
}

void main() {
runApp(new MyApp());
}