Duplicate classes from androidx and com.android.support

I recently updated my Android Studio (and I'm pretty sure the Gradle version), and now I've been getting a bunch of errors when trying to compile my project. Here's the one that is plaguing me at the moment:

Duplicate class android.support.v4.app.INotificationSideChannel found in modules classes.jar (androidx.core:core:1.0.1) and classes.jar (com.android.support:support-compat:26.1.0)

This is followed by lots of similar ones.

I tried removing all uses of com.android.support in favor of androidx (see here for what I was using the replace things), but com.android.support libraries are still being used, even when I delete the libraries (they're just remade once I try to compile again).

Here's a link to the full error I get.

Add these lines to your gradle.properties

android.useAndroidX=true
android.enableJetifier=true

If gradle.properties is absent, create the file in the root directory of your project.

It looks like you have some support relics anywhere in your dependencies, maybe from a lib? To investigate and see the dependencies tree, please run:

./gradlew :yourApp:dependencies

and then you see from where it comes.

In your app build.gradle you are using a mix of old support library and new support library artifacts. Remove one of them from your build.gradle to resolve this issue.

Old artifact: com.android.support:support-compat

Corresponding new artifact: androidx.core:core:1.0.0

See this page for more information on migrating to AndroidX.

Like others says, the solution is to migrating to AndroidX, it works for me. However, it isn´t an easy way and it requires a bit of pacience... These are the steps that I did:

• First, is very important that you do all this changes in a different branch or you make a backup of your project.

• You need to have the Android Gradle Plugin Version 3.5.1. So, in build.gradle set:

dependencies {
    classpath 'com.android.tools.build:gradle:3.5.1'
}

• Migrate to AndroidX using Android Studio Tool : Refactor --> Migrate to AndroidX...

• When it finishes, it has done all pertinents modification, but posibly you can´t deploy the project correctly because you find any errors. These are the problems that I found and the solutions:

• If you use Kotlin, in build.gradle set:

buildscript {
    ext.kotlin_version = '1.3.10'
}

and

compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"

• If you use destination method, add "file" parameter: destination file("$reportsDir/checkstyle/checkstyle.xml")
• If you use Butterknife, use 10.0.0 version
• Finally, Build --> Clean Project and Build --> Rebuild Project

This solution from here worked the best for me. Migrating to androidX

https://developer.android.com/jetpack/androidx/migrate

> With Android Studio 3.2 and higher, you can migrate an existing > project to AndroidX by selecting Refactor > Migrate to AndroidX from > the menu bar. > > The refactor command makes use of two flags. By default, both of them > are set to true in your gradle.properties file: > > android.useAndroidX=true The Android plugin uses the appropriate > AndroidX library instead of a Support Library. > android.enableJetifier=true The Android plugin automatically migrates > existing third-party libraries to use AndroidX by rewriting their > binaries.

If you face any issue regarding duplicate classes after using Facebook mediation and google ad libraries so follow these steps:

1- Add this in build.gradle(Module) in Top

apply plugin: 'com.google.firebase.crashlytics'
apply plugin: 'com.google.gms.google-services'

2- Add this in build.gradle(Module) -> android

 packagingOptions {
        exclude "META-INF/DEPENDENCIES"
    }

3- Add this in build.gradle(Module) -> dependencies

    //firebase bom
    implementation platform('com.google.firebase:firebase-bom:29.2.0')
    implementation 'com.google.firebase:firebase-crashlytics'
    implementation 'com.google.firebase:firebase-analytics'
    implementation 'com.google.firebase:firebase-messaging:23.0.1'

    //ADS
    def ads_version = "20.6.0"
    implementation "com.google.android.gms:play-services-ads:$ads_version"

    //facebook ads
    implementation 'com.google.ads.mediation:facebook:6.8.0.0'

4- Add this in build.gradle(Project )-> buildscript-> dependencies

classpath "com.android.tools.build:gradle:7.0.4"
classpath 'com.google.gms:google-services:4.3.10'
classpath 'com.google.firebase:firebase-crashlytics-gradle:2.8.1'

5- Add this in gradle.wrapper.propertise

#Wed Dec 16 15:32:03 PKT 2020
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https://services.gradle.org/distributions/gradle-7.0.2-bin.zip