Error while Dexing when building Flutter project - firebase

Question

I am currently trying to integrate Firebase Messaging into my project, I have set up a firebase project and successfully imported all of the other dependencies I need (crashlytics, firestore etc...)
however when I add the firebase messaging dependency to my pubspec.yaml I get an error when building. I am using the newest version of firebase_messaging and also the newest version of google services.
The Error:
Plugin project: firebase_core_web not found. Please update settings.gradle.
Invalid depfile: C:\Users\Owner\AndroidStudioProjects\switcheroo_ios\.dart_tool\flutter_build\d71b8b11f916190e0bd095c78ccf0a69\kernel_snapshot.d
Invalid depfile: C:\Users\Owner\AndroidStudioProjects\switcheroo_ios\.dart_tool\flutter_build\d71b8b11f916190e0bd095c78ccf0a69\kernel_snapshot.d
AGPBI: {"kind":"error","text":"Type com.google.firebase.iid.zzbb is referenced as an interface from `com.google.firebase.messaging.zzf`.","sources":[{}],"tool":"D8"}
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:mergeExtDexDebug'.
> Could not resolve all files for configuration ':app:debugRuntimeClasspath'.
> Failed to transform artifact 'firebase-messaging.aar (com.google.firebase:firebase-messaging:20.0.1)' to match attributes {artifactType=android-dex, dexing-enable-desugaring=true, dexing-is-debuggable=true, dexing-min-sdk=21}.
> Execution failed for DexingWithClasspathTransform: C:\Users\Owner\.gradle\caches\transforms-2\files-2.1\ac2c922e894bed89371853ed7d90bb4e\jetified-firebase-messaging-20.0.1\jars\classes.jar.
> Error while dexing.
App Gradle:
def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
localPropertiesFile.withReader('UTF-8') { reader ->
localProperties.load(reader)
}
}
def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}
def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
flutterVersionCode = '1'
}
def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
flutterVersionName = '1.0'
}
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
apply plugin: 'com.google.gms.google-services'
apply plugin: 'com.google.firebase.crashlytics'
android {
compileSdkVersion 28
sourceSets {
main.java.srcDirs += 'src/main/kotlin'
}
lintOptions {
disable 'InvalidPackage'
}
defaultConfig {
// TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
applicationId "com.barbecu.switcherooIOS"
minSdkVersion 21
targetSdkVersion 28
versionCode flutterVersionCode.toInteger()
versionName flutterVersionName
}
buildTypes {
release {
// TODO: Add your own signing config for the release build.
// Signing with the debug keys for now, so `flutter run --release` works.
signingConfig signingConfigs.debug
}
}
}
flutter {
source '../..'
}
dependencies {
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'com.google.firebase:firebase-crashlytics:17.0.1'
}
Project Gradle:
buildscript {
ext.kotlin_version = '1.3.50'
repositories {
google()
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:3.5.0'
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
classpath 'com.google.gms:google-services:4.3.3'
classpath 'com.google.firebase:firebase-crashlytics-gradle:2.1.1'
}
}
allprojects {
repositories {
google()
jcenter()
}
}
rootProject.buildDir = '../build'
subprojects {
project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
project.evaluationDependsOn(':app')
}
task clean(type: Delete) {
delete rootProject.buildDir
}

Answer 1

Try adding
implementation 'com.google.firebase:firebase-messaging:20.0.1'
inside dependencies
just try adding dependencies that r related to each platform explicitly like in android as above
for ios (im not sure about ios ecosystem) but adding this might help
pod 'Firebase/Messaging'

Answer 2

1.- In build.gradle (project level) use:
classpath 'com.google.gms:google-services:4.3.3' // Google Services plugin
2.- In build.gradle (app level) use:
minSdkVersion 21
3.- Replace settings.gradle content with the solution provided here:
Plugin project :firebase_core_web not found