Duplicate classes from androidx and com.android.support

Add these lines to 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.