Duplicate files while including butterknife with g

Question

I have a basic Android app that I created with Android Studio, and I'm having problems adding butterknife to my build. I get this error:

Error:: duplicate files during packaging of APK C:\apps\orion\app\build\apk\app-debug-unaligned.apk
Error:Execution failed for task ':app:packageDebug'.
> Duplicate files copied in APK META-INF/services/javax.annotation.processing.Processor
    File 1: C:\Users\andres\.gradle\caches\modules-2\files-2.1\com.jakewharton\butterknife\4.0.1\f43b36925363701633d01adb8e54df7150397a78\butterknife-4.0.1.jar
    File 2: C:\Users\andres\.gradle\caches\modules-2\files-2.1\com.jakewharton\butterknife\4.0.1\f43b36925363701633d01adb8e54df7150397a78\butterknife-4.0.1.jar

My dependencies look like this:

dependencies {

    compile 'com.android.support:support-v4:+'
    compile 'com.squareup.dagger:dagger-compiler:1.2.1'
    compile 'com.squareup.dagger:dagger:1.2.1'
    compile 'com.jakewharton:butterknife:4.0.1'
    compile 'com.google.android.gms:play-services:4.0.30'
    compile 'com.android.support:appcompat-v7:+'
    compile project(':lib')
    compile fileTree(dir: 'libs', include: ['*.jar'])
}

Answer 1

Later versions of the plugin will tell you how to fix this. I think we introduced the fix in 0.8 so you should probably upgrade. Then the fix is to put this in your build.gradle

android {
    packagingOptions {
        exclude 'META-INF/services/javax.annotation.processing.Processor'
    }
}

This will exclude this file from the packaging which is fine since it's not actually needed in the APK.

Answer 2

That's because you wrote compile for dagger-compiler, replace it with provided and the issue will be fixed.

compile 'com.squareup.dagger:dagger:1.2.1'
provided 'com.squareup.dagger:dagger-compiler:1.2.1'

Answer 3

The best option in version >= 0.9.1 of Gradle build tools is probably:

android {
    packagingOptions {
        pickFirst 'META-INF/services/javax.annotation.processing.Processor'
    }
}

For more, see the Android Tools Project page: New Build System.

Edit: One last note here if you start having problems with generated code, make sure to structure your dependencies properly. I ended up removing any exclusion of the Processor line and structuring my annotation processed dependencies like:

compile "org.parceler:parceler-api:0.2.15"
apt "org.parceler:parceler:0.2.15"

and

provided 'com.squareup.dagger:dagger-compiler:1.2.2'
apt 'com.squareup.dagger:dagger-compiler:1.2.2'