Why does adding google firebase cause a Dex error?

Question

Adding

implementation 'com.google.firebase:firebase-core:11.8.0'

to my module gradle file gives me errors suggesting I have over 64K methods in my project.

My guess is that I'm somehow implement the whole google play services, although adding

implementation 'com.google.android.gms:play-services-maps:11.8.0'

or

implementation 'com.google.android.gms:play-services-location:11.8.0'

give me no errors.

Gradel:

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.2"
    defaultConfig {
        applicationId "se.workshop.collect"
        minSdkVersion 21
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        vectorDrawables.useSupportLibrary = true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation 'uk.co.chrisjenx:calligraphy:2.3.0'
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation 'com.android.support:support-v4:26.1.0'
    implementation 'com.android.support:recyclerview-v7:26.1.0'
    implementation 'uk.co.chrisjenx:calligraphy:2.3.0'
    implementation 'com.google.android.gms:play-services-maps:11.8.0'
    implementation 'com.google.android.gms:play-services-location:11.8.0'
    implementation 'com.google.firebase:firebase-core:11.8.0'
    implementation "com.android.support:recyclerview-v7:26.1.0"                //Recycler View Support
    implementation "com.android.support:cardview-v7:26.1.0"                //Recycler View Support
    implementation 'com.squareup.okhttp3:okhttp:3.9.0'
    implementation 'com.google.code.gson:gson:2.8.2'
    implementation "com.fasterxml.jackson.module:jackson-module-kotlin:2.9.0"
    implementation 'com.karumi:dexter:4.2.0'
    implementation 'com.android.support:design:26.1.0'
    implementation 'com.android.support:support-vector-drawable:26.1.0'
    implementation group: 'org.jetbrains.kotlin', name: 'kotlin-reflect', version:"$kotlin_version"
    testImplementation 'junit:junit:4.12'
    androidTestImplementation('com.android.support.test.espresso:espresso-core:3.0.1', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })

}

and the errors:

Error:The number of method references in a .dex file cannot exceed 64K.
Learn how to resolve this issue at https://developer.android.com/tools/building/multidex.html
Error:com.android.dex.DexIndexOverflowException: method ID not in [0, 0xffff]: 65536
Error:  at com.android.dx.merge.DexMerger$8.updateIndex(DexMerger.java:565)
Error:  at com.android.dx.merge.DexMerger$IdMerger.mergeSorted(DexMerger.java:276)
Error:  at com.android.dx.merge.DexMerger.mergeMethodIds(DexMerger.java:574)
Error:  at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:166)
Error:  at com.android.dx.merge.DexMerger.merge(DexMerger.java:198)
Error:  at com.android.builder.dexing.DexArchiveMergerCallable.call(DexArchiveMergerCallable.java:61)
Error:  at com.android.builder.dexing.DexArchiveMergerCallable.call(DexArchiveMergerCallable.java:36)
Error:  at java.util.concurrent.ForkJoinTask$AdaptedCallable.exec(ForkJoinTask.java:1424)
Error:  at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
Error:  at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
Error:  at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
Error:  at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Error:Execution failed for task ':app:transformDexArchiveWithDexMergerForDebug'.
> com.android.build.api.transform.TransformException: com.android.dex.DexIndexOverflowException: method ID not in [0, 0xffff]: 65536
Information:BUILD FAILED in 13s

Answer 1

The simple answer to the question stated in the subject is that the dependency you added simply pushed the total number of methods above 64K, as you see in the error message. It sounds like you're assuming that it should not, but obviously it is. Bear in mind that firebase-core also brings in firebase-analyics and some other libraries, so you're actually getting more than just firebase-core when you add it.

In any event, you should enable multidex in your builds to prevent this error as you add more libraries.