Unable to Merge Dex - Android Studio 3.0

Question

When I updated my Android Studio to 3.0 in the stable channel and ran the project, I started getting the below error.

Error:Execution failed for task ':app:transformDexArchiveWithExternalLibsDexMergerForDebug'.
com.android.builder.dexing.DexArchiveMergerException: Unable to merge dex

I tried cleaning and rebuilding the project, but it didn't work. Any help will be appreciated.

Project level build.gradle

buildscript {
repositories {
    jcenter()
    google()
}
dependencies {
    classpath 'com.android.tools.build:gradle:3.0.0'
    classpath 'com.google.gms:google-services:3.1.0'


    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files
}
} 
allprojects {
repositories {
    jcenter()
    google()
}
}
task clean(type: Delete) {
delete rootProject.buildDir
}

App level build.gradle

apply plugin: 'com.android.application'
android {
compileSdkVersion 26
buildToolsVersion '26.0.2'
defaultConfig {
    applicationId "com.med.app"
    minSdkVersion 21
    targetSdkVersion 26
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    resConfigs "auto"
    multiDexEnabled true

}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
})

compile 'com.android.support.constraint:constraint-layout:1.0.2'
testCompile 'junit:junit:4.12'

//appcompat libraries
compile 'com.android.support:appcompat-v7:26.1.0'
compile 'com.android.support:design:26.1.0'


//butterknife
compile 'com.jakewharton:butterknife:8.8.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

//picasso
compile 'com.squareup.picasso:picasso:2.5.2'

//material edittext
compile 'com.rengwuxian.materialedittext:library:2.1.4'

// Retrofit & OkHttp & and OkHttpInterceptor & gson
compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'
compile 'com.google.code.gson:gson:2.8.2'
compile 'com.squareup.okhttp3:logging-interceptor:3.8.0'

// FirebaseUI for Firebase Auth
compile 'com.firebaseui:firebase-ui-auth:3.1.0'
}
apply plugin: 'com.google.gms.google-services'

I have tried all the answers given but I am unable to solve this error. Please help.

Answer 1

Add an explicit dependency to play-services-auth along with your firebase-ui-auth dependency:

// FirebaseUI for Firebase Auth
    compile 'com.firebaseui:firebase-ui-auth:3.1.0'
    compile 'com.google.android.gms:play-services-auth:11.4.2'

This is because firebase-ui-auth has a transitive dependency to play-services-auth and must be used with the corresponding version of play-services-auth. Please see this explanation.

firebase-ui-auth
|--- com.google.firebase:firebase-auth
|--- com.google.android.gms:play-services-auth

Earlier versions of the Gradle build tool did not include transitive dependencies so now versions can conflict with other play-services versions.

My Issue Explained and Answered (In case anyone wants to know)

When you upgrade to Android Studio 3.0 and update the gradle build tool version to 3.0.0, compiling of dependencies is now done differently than in earlier versions.

I recently encountered the same issue. I was using these dependencies which worked fine through Gradle version 2.3.3:

implementation 'org.apache.httpcomponents:httpmime:4.3.6'
implementation 'org.apache.httpcomponents:httpclient-android:4.3.5.1'

After the upgrade to gradle-build-version 3.0.0, I got the same error. Digint into it, I found that the transitive dependency of httpmime conflicted with the file httpclient-android was including.

Description

Let me explain this in detail. Earlier, while using gradle-tool-version 2.3.3, I was using httpclient-android to fetch and use the class named org.apache.http.entity.ContentType.java Expanding the transitive dependencies of org.apache.httpcomponents:httpmime:4.3.6 showed that it has org.apache.httpcomponents:httpcore:4.3.6 which is the same package I wanted to use. But while compiling or syncing the build, it was excluding org.apache.http.entity.ContentType.java so I needed to add this dependency which includes ContentType.java:

implementation 'org.apache.httpcomponents:httpclient-android:4.3.5.1'

Everything worked fine after that.

Once I upgraded the gradle-build-version to 3.0.0, things changed. It now included all transitive dependencies. So while compiling with the latest Android Studio with gradle-build-tool version 3.0.0, my ContentType.java was being compiled twice. Once from org.apache.httpcomponents:httpcore:4.3.6 (which is an implicit transitive dependency of httpmime) and again from org.apache.httpcomponents:httpclient-android:4.3.5.1 which I was using earlier.

To resolve this issue I had to remove the existing org.apache.httpcomponents:httpclient-android:4.3.5.1 dependency as httpmime would itself fetch the relevant class required for my application.

The solution for my situation: only use required dependencies and remove the httpclient-android

implementation 'org.apache.httpcomponents:httpmime:4.3.6'

Note that this is just the case for me. You'll need to dig into your own dependencies and apply the solution accordingly.