Using RxJava 2 and Retrofit 2, adapter version issue

Question

I've added a new library module to existing application module in Android Studio. The main difference was adding RxJava 2 and Retrofit 2. After updating build.gradle of new module I started to get next error:

Error:Execution failed for task ':app:transformResourcesWithMergeJavaResForBetaNewApiDebug'. com.android.build.api.transform.TransformException: com.android.builder.packaging.DuplicateFileException: Duplicate files copied in APK META-INF/rxjava.properties File1: C:\Users\Gaket.gradle\caches\modules-2\files-2.1\io.reactivex.rxjava2\rxjava\2.0.2\cfccdd18cdfbe7b4773d42c9f3512eeafbe5cbf9\rxjava-2.0.2.jar File2: C:\Users\Gaket.gradle\caches\modules-2\files-2.1\io.reactivex\rxjava\1.1.5\ece7b5d0870e66d8226dab6dcf47a2b12afff061\rxjava-1.1.5.jar

I see that there is some problem with RxJava (I want to try RxJava 2 and here I see both RxJava 1 and RxJava 2). The problem arises right after adding all dependencies, we do not use RxJava in our main application.

Update: As I mentioned below, I checked three topics (you can see it below). This issue: possible duplicate is similar to the one that I already mention below: this one. Both of them have workarounds that do not take into account the real problem that I underlined in my answer. And the answer is "There is no production-ready adapter from Retrofit 2 to RxJava 2 at the moment" (full details described in answer below).

I checked several topics: first is some concrete solution for a concrete problem, second talks about rxbindings, but I don't use them, some others also have not resolved my problem or look like total workarounds this one. I tried to google "rxjava 2 and retrofit 2" but haven't found a solution.

Here is the build.gradle of library:

apply plugin: 'com.android.library'
apply plugin: 'com.jakewharton.butterknife'

android {
compileSdkVersion 25
buildToolsVersion "25.0.0"

defaultConfig {
    minSdkVersion 15
    targetSdkVersion 24
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

}
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:appcompat-v7:$supportLibraryVersion"
compile "com.android.support:recyclerview-v7:$supportLibraryVersion"

compile 'io.reactivex.rxjava2:rxjava:2.0.2'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'com.squareup.okhttp3:okhttp:3.5.0'
compile 'com.squareup.retrofit2:retrofit:2.1.0'
compile 'com.squareup.retrofit2:converter-gson:2.1.0'
compile 'com.squareup.retrofit2:adapter-rxjava:2.1.0'
compile "com.makeramen:roundedimageview:1.3.0"

annotationProcessor 'com.jakewharton:butterknife-compiler:8.4.0'
provided 'javax.annotation:jsr250-api:1.0'
compile 'com.jakewharton:butterknife:8.4.0'

testCompile 'junit:junit:4.12'

}

The question is:
Why does this problem happen and what is the proper way to handle it?

Answer 1

You should use the official adapter for the second version of RxJava:

compile 'com.squareup.retrofit2:adapter-rxjava2:2.2.0 // works with RxJava 2

The fact that adapter has version 2.*.* does not mean that it is intended for use with RxJava 2, as I thought.

compile 'com.squareup.retrofit2:adapter-rxjava:2.1.0' // won't work with RxJava 2

Previously, you should use a temporary version: Here is the repository of Jake Wharton with Retrofit 2 to RxJava 2 adapter.

I found this problem using command gradlew :app dependencies in Android Studio terminal, where the app is name of my library module. There I looked for "rxjava" keyword and found different versions of it.

Update: On February, 21 Square published the official version of adapter, as Darshan Mistry pointed out in a comment. Answer updated.