Implemention Ironsource to Flitter

Question

I am using Ironsource in flutter Here

ironsource_mediation: 1.1.0 google_mobile_ads: 2.3.0

buld.gradle(app):

implementation 'com.google.android.gms:play-services-ads-identifier:18.0.1' 
implementation 'com.google.android.gms:play-services-basement:18.1.0'
implementation 'com.google.android.gms:play-services-appset:16.0.2'

implementation 'com.ironsource.sdk:mediationsdk:7.2.7' 
// Add AdMob and Ad Manager Network
implementation 'com.google.android.gms:play-services-ads:21.4.0' 
implementation 'com.ironsource.adapters:admobadapter:4.3.34'
// Add Facebook Network
implementation 'com.ironsource.adapters:facebookadapter:4.3.38'
implementation 'com.facebook.android:audience-network-sdk:6.12.0'

buld.gradle:

repositories {google()mavenCentral()maven { url 'https://android-sdk.is.com/' }}

AndroidManifest.xml:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.FLASHLIGHT" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
<uses-permission android:name="com.google.android.gms.permission.AD_ID"/>
<uses-permission android:name="com.android.vending.BILLING"/>
<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />


    <meta-data
        android:name="com.google.android.gms.ads.APPLICATION_ID"
        android:value= "@string/android__admob_ads_id_key" /> 

**But Ireceive this error:**

E/flutter (12382): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: PlatformException(ERROR, Activity is null, null, null) E/flutter (12382): #0 StandardMethodCodec.decodeEnvelope message_codecs.dart:653 E/flutter (12382): #1
MethodChannel._invokeMethod platform_channel.dart:315 E/flutter (12382): E/flutter (12382): I/flutter (12382): PlatformException(ERROR, Activity is null, null, null)

How can I implement and configure ironsource in flutter?