Develop Reference

Android APK artifact name with respective ABI architecture

I am trying to extract and use the architecture of the artifact to compose the output file name:
void defineDefaultVariantsAPK(String appName) {
defineVariantsAPK({ variant, output ->
def versionName = variant.versionName
def versionCode = "-(${variant.versionCode}"
def buildLetter = variant.buildType.name == "release" ? "-R" : "-D"
def flavor = variant.productFlavors.size() > 0 ? "-${variant.productFlavors[0].name}" : ""
def architecture = "-" + output.getFilter(com.android.build.OutputFile.ABI)
"v${versionName}${versionCode}${buildLetter}${flavor}${architecture}--${appName}.apk"
})
}
void defineVariantsAPK(Closure nameBuild) {
android {
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File((String) output.outputFile.parent, nameBuild(variant, output))
}
}
}
}
for some reason many posts says that that is the solution, but my gradle fails on:
> Could not get unknown property 'com' for project ':app' of type org.gradle.api.Project.
I've tried to use import:
unable to resolve class com.android.build.OutputFile
configuration:
com.android.tools.build:gradle:2.3.3
Gradle version 3.5
So I really wonder, what am I doing different that it doesn't work?

Beggining with Gradle 3.0.0 you can do it like this:
applicationVariants.all { variant ->
variant.outputs.all { output ->
def appName = "AppName_"
def buildType = variant.variantData.variantConfiguration.buildType.name
def architecture = output.getFilter(com.android.build.OutputFile.ABI)
def newName
if (buildType == 'debug') {
newName = "${appName}debug_${defaultConfig.versionName}_${architecture}.apk"
} else {
newName = "${appName}release_${defaultConfig.versionName}_${architecture}.apk"
}
outputFileName = newName
}
}
*put this in your module(app) build.gradle file.

This code works for me with gradle 3+ for android
android.applicationVariants.all { variant ->
variant.outputs.all { output ->
def architecture = output.filters[0].identifier
outputFileName = "myapp-${architecture}-${variant.versionName}.apk"
}
}

Where did you define this function? Try to move it you your app/build.gradle file as that is where buildscript is and gradle loads classes from it into classpath.

So following #blazsolar suggestion I've moved the method to the app build gradle file, the move itself was not the solution, when I tried to add the import:
import com.android.build.OutputFile
for some reason the IDE (Android studio) has decided to delete the import..
but once I've this import:
import com.android.build.OutputFile.FilterType
it was just fine!
but that is not the end of it... I want the method to be in a common gradle file, that all my project can reuse.
once I've added the last import to the common gradle file... the import figging disappeared again..
I am left with yet another question
update:
So I've update Android plugin and gradle version to 3.0.1 and 4.1 respectively, and now... things have change.. now there is no
com.android.build.OutputFile.FilterType
Now you need to use:
com.android.build.VariantOutput.ABI
Just in case anyone wonder...

Cannot set the value of read-only property 'outputFile' for ApkVariantOutputImpl_Decorated

I was using the following code in my gradle script to rename the apks generated with AndroidStudio:
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File(output.outputFile.parent, defaultConfig.versionCode + "_" + output.outputFile.name)
}
}
So it was generating apks with names like: 345-app-release.apk, where 345 is the versionCode.
But after updating to AndroidStudio 3.0 it returns the following error:
Cannot set the value of read-only property 'outputFile' for
ApkVariantOutputImpl_Decorated{apkData=Main{type=MAIN, fullName=debug,
filters=[]}} of type
com.android.build.gradle.internal.api.ApkVariantOutputImpl.
How can I achieve a similar renaming with the new build tools.

Use output.outputFileName instead of output.outputFile

2019 - Simple Solution for Gradle 3.0+** and 3.1.0
To change the name of the APK in Android
android { //add inside the android {}
......
applicationVariants.all { variant ->
variant.outputs.all {
def flavor = variant.name
def versionName = variant.versionName
outputFileName = "prefix_${flavor}_${versionName}.apk"
}
}
}
prefix_release_1.0.1.apk

Try this code :
buildTypes {
applicationVariants.all { variant ->
variant.outputs.each { output ->
def name = "myapp_v${variant.versionName}(${variant.versionCode}).apk"
output.outputFileName = name
}
}
}

In or After gradle 3.1.0
try below code
applicationVariants.all { variant ->
variant.outputs.all { output ->
outputFileName = new File(
"release_build", // here you can change the name
output.outputFile.name)
}
}

In my case I resolved it by just refusing to update to Gradle 4.4 (in my case).So when Studio asks (when you open your project for the first time) you to update Gradle to support instant run,etc just simply refuse and you should be fine.

What worked for me was to
1. change each to "all"
2. change output.outputFile to "outputFileName"
3. Run $./gradlew clean build in terminal
For example, if your artifacts.gradle settings were this:
android.applicationVariants.all { variant ->
variant.outputs.each { output ->
def finalVersionCode = 10000 + versionCode
output.versionCodeOverride = finalVersionCode
output.outputFile = new File(
output.outputFile.parent, output.outputFile.name.replace(".apk","-${finalVersion}.apk"))
}
}
Then you would want to change it to this:
android.applicationVariants.all { variant ->
variant.outputs.all { output ->
def finalVersionCode = 10000 + versionCode
output.versionCodeOverride = finalVersionCode
outputFileName = new File(
output.outputFile.parent,
outputFileName.replace(".apk", "-${finalVersionCode}.apk"))
}
}

change your code into:-
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File(output.outputFile.parent, "${variant.applicationId}-${variant.versionName}.apk")
}
}

How to change the proguard mapping file name in gradle for Android project

I have android project based on gradle and I want to change mapping.txt file name after it's generated for my build. How can it be done?
upd
How it can be done in build.gradle? Since I have access there to my flavors and other stiff, I would like to create mapping file name based on flavor/build variant version.

Simpler solution.
applicationVariants.all { variant ->
if (variant.getBuildType().isMinifyEnabled()) {
variant.assemble.doLast {
copy {
from variant.mappingFile
into "${rootDir}/proguardTools"
rename { String fileName ->
"mapping-${variant.name}.txt"
}
}
}
}
}

As of today (May 2020) former solution, which uses variant.mappingFile is not working anymore in new Android Gradle plugin (Android Studio) 3.6 and higher.
Instead variant.mappingFile returns null and following is displayed in the logs:
WARNING: API 'variant.getMappingFile()' is obsolete and has been replaced with 'variant.getMappingFileProvider()'.
I am sharing my working solution, which uses new api:
applicationVariants.all { variant ->
variant.assembleProvider.get().doLast {
def mappingFiles = variant.getMappingFileProvider().get().files
for (file in mappingFiles) {
if (file != null && file.exists()) {
def nameMatchingApkFile = "$archivesBaseName-$variant.baseName-$file.name"
def newMappingFile = new File(file.parent, nameMatchingApkFile)
newMappingFile.delete() //clean-up if exists already
file.renameTo(newMappingFile)
}
}
}
}
Note, that variant.getBuildType().isMinifyEnabled() is not used since we are using DexGuard.
The code above makes mapping file's name match apk's file name.
Just in case, if you need to change apk name - following could be used:
android {
defaultConfig {
//resulting apk will looks like: "archive base name" + -<flavour>-<buildType>.apk
archivesBaseName = "$applicationId-$versionName"
}
}

Use this command in your proguard-rules.pro file:
-printmapping path/to/your/file/file_name.txt
the file will be written in part {root}/path/to/your/file with file_name.txt name.
If you want to have different setting for different flavors you can define many proguard-rules for them
I found one more idea but I am not sure that it is right way.
You can define your path in flavors:
productFlavors {
test1 {
applicationId "com.android.application.test"
project.ext."${name}Path" = 'path/one/mapp.txt'
}
test2 {
project.ext."${name}Path" = 'path/two/mapp.txt'
}
}
And as next you can define new task before $asseble{variant.name.capitalize()} task as is shown below:
android.applicationVariants.all { variant ->
def envFlavor = variant.productFlavors.get(0).name
def modifyProguardPath = tasks.create(name: "modifyProguardFor${variant.name.capitalize()}", type: Exec) {
def pathToMap = project."${envFlavor}Test1"
doFirst {
println "==== Edit start: $pathToMap ===="
}
doLast {
println "==== Edit end: $pathToMap ===="
}
executable "${rootDir}/utils/test.bash"
args pathToMap
}
project.tasks["assemble${variant.name.capitalize()}"].dependsOn(modifyProguardPath);
}
and in script ${root}/utils/test.bash - you can modify proguard-rules.pro.
But I think that exist better solution.

Many thanx to Sergii Pechenizkyi who helped me to found this good solution.
To implement copying of proguard mapping files for each flavor we can create "root" task copyProguardMappingTask and number of dynamic tasks for each flavor
def copyProguardMappingTask = project.tasks.create("copyProguardMapping")
applicationVariants.all { variant ->
variant.outputs.each { output ->
...
if (variant.getBuildType().isMinifyEnabled()) {
def copyProguardMappingVariantTask = project.tasks.create("copyProguardMapping${variant.name.capitalize()}", Copy)
def fromPath = variant.mappingFile;
def intoPath = output.outputFile.parent;
copyProguardMappingVariantTask.from(fromPath)
copyProguardMappingVariantTask.into(intoPath)
copyProguardMappingVariantTask.rename('mapping.txt', "mapping-${variant.name}.txt")
copyProguardMappingVariantTask.mustRunAfter variant.assemble
copyProguardMappingTask.dependsOn copyProguardMappingVariantTask
}
}
}
afterwards we should run this task after assembling our project. I use jenkins and my tasks option looks like
gradle clean assembleProjectName copyProguardMapping
It works like a charm.

Since the last update variant.mappingFile is not longer available.
(I use ProGuard version 4.7, AndroidStudio 2.0)
This is (part of) my build.gradle file:
import java.util.regex.Matcher
import java.util.regex.Pattern
def getCurrentFlavor() {
Gradle gradle = getGradle()
String tskReqStr = gradle.getStartParameter().getTaskRequests().toString()
Pattern pattern;
if( tskReqStr.contains( "assemble" ) )
pattern = Pattern.compile("assemble(\\w+)(Release|Debug)")
else
pattern = Pattern.compile("generate(\\w+)(Release|Debug)")
Matcher matcher = pattern.matcher( tskReqStr )
if( matcher.find() )
return matcher.group(1).toLowerCase()
else
{
println "NO MATCH FOUND"
return "";
}
}
buildTypes {
release {
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
minifyEnabled true
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File(output.outputFile.parent, "${variant.name}_v${variant.versionName}.apk")
}
def mappingFile = "${rootDir}\\app\\build\\outputs\\mapping\\${getCurrentFlavor()}\\release\\mapping.txt"
println("mappingFile: ${mappingFile}")
if (variant.getBuildType().isMinifyEnabled()) {
variant.assemble.doLast {
copy {
from "${mappingFile}"
into "${rootDir}"
rename { String fileName ->
"mapping-${variant.name}.txt"
}
}
}
}
}
}
debug {
minifyEnabled false
useProguard false
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File(output.outputFile.parent, "${variant.name}_v${variant.versionName}.apk")
}
}
}
}

variant.assemble is now deprecated, suggested solution incorporating previous modifications:
archivesBaseName = "MyCompany-MyAppName-$versionName"
...
applicationVariants.all { variant ->
variant.assembleProvider.get().doLast {
if (variant.mappingFile != null && variant.mappingFile.exists()) {
def mappingFilename = "$archivesBaseName-$variant.baseName-mapping.txt"
(new File(variant.mappingFile.parent, mappingFilename)).delete()
variant.mappingFile.renameTo(variant.mappingFile.parent +
"/" + mappingFilename)
}
}
}
If using app bundle (aab) instead of apk, add this to after the android section:
afterEvaluate {
bundleRelease.doLast {
android.applicationVariants.all { variant ->
if (variant.buildType.name == 'release') {
tasks.create(name: "renameMappingFile") {
if (variant.mappingFile != null && variant.mappingFile.exists()) {
variant.mappingFile.renameTo(variant.mappingFile.parent + "/$variant.baseName-$versionName-${new Date().format('yyyy-MM-dd_HHmm')}-mapping.txt")
}
}
}
}
}
}
Swap bundleRelease for assembleRelease for apks in the last example too.
Update: However that last doesn't work if you try and build a normal debug directly to your phone then. Error:
Could not get unknown property 'bundleRelease' for project ':app' of type org.gradle.api.Project.

This is a variation of igorpst's answer but renames mapping.txt to match the apk's name exactly including the app version name. I've combined this with code to name the APK with a version number as described in this answer. I had to snoop through the gradle source code to find $variant.baseName
apply plugin: 'com.android.application'
android {
compileSdkVersion 21
buildToolsVersion "21.1.2"
defaultConfig {
applicationId "com.company.app"
minSdkVersion 13
targetSdkVersion 21
versionCode 14 // increment with every release
versionName '1.4.8' // change with every release
archivesBaseName = "MyCompany-MyAppName-$versionName"
}
applicationVariants.all { variant ->
if (variant.getBuildType().isMinifyEnabled()) {
variant.assemble.doLast {
(new File(variant.mappingFile.parent, "$archivesBaseName-$variant.baseName-mapping.txt")).delete();
variant.mappingFile.renameTo(variant.mappingFile.parent +
"/$archivesBaseName-$variant.baseName-mapping.txt")
}
}
}
}

All these answers used copy to rename the file.
I didn't want to move the file however, I just wanted to change it's name, keeping in mind the build type and flavor.
I based myself on the code from the other posters here and changed it up a bit.
Since Minify can be false, while still using proguard, I just check if the file is present.
Following code accomplishes just that.
android {
applicationVariants.all { variant ->
variant.assemble.doLast {
def mappingFolderUrl = "${project.buildDir.path}/outputs/mapping/"
if (variant.buildType.name) {
mappingFolderUrl += variant.buildType.name + "/"
}
if (variant.flavorName) {
mappingFolderUrl += variant.flavorName + "/"
}
def mappingFileUrl = mappingFolderUrl + "mapping.txt"
logger.lifecycle("mappingFile path: ${mappingFileUrl}")
File mappingFile = file(mappingFileUrl)
if (mappingFile.exists()) {
def newFileName = mappingFolderUrl + "mapping-${variant.name}.txt"
mappingFile.renameTo(newFileName)
}
}
}
}
NOTE
You could probably use this code to move the file as well.
the .renameTo() method expects a full path, If you change the path, I would suppose you effectively move the File to another place.

A complete solution that worked for me
applicationVariants.all { variant ->
def variantType = variant.buildType.name
if (variantType == "release") {
variant.assemble.doLast {
def mappingFile = variant.mappingFile
mappingFile.renameTo(mappingFile.parent + "/mapping-${variant.name}.txt")
}
}
}

For Android Studio Gradle Plugin Version 4.1.0 and newer (since about May 2020)
This version fixes the following warning:
WARNING: API 'variant.getMappingFile()' is obsolete and has been replaced with 'variant.getMappingFileProvider()'.
applicationVariants.all { variant ->
variant.assembleProvider.get().doLast {
def mappingFileProvider = variant.getMappingFileProvider().get()
if (mappingFileProvider != null) {
try {
def mappingFiles = mappingFileProvider.getFiles()
for (mappingFile in mappingFiles) {
if (mappingFile != null && mappingFile.exists()) {
def newMappingFileName = "$archivesBaseName-$variant.baseName-$mappingFile.name"
project.logger.lifecycle("Renaming '${mappingFile.name}' to '${newMappingFileName}'")
def newMappingFile = new File(mappingFile.parent, newMappingFileName)
newMappingFile.delete()
mappingFile.renameTo(newMappingFile)
}
}
} catch (Exception ignored) {
project.logger.lifecycle("No mapping files found to rename")
}
}
}
}
For Android Studio Gradle Plugin Version 3.3.0 (January 2019) through about May 2020
This overcomes previous issues where Android 3.0/Android Gradle Plugin 3.0 deprecated BuildType.isMinifyEnabled() and the gradle plugin deprecated variant.getAssemble().
applicationVariants.all { variant ->
variant.assembleProvider.get().doLast {
if (variant.mappingFile != null && variant.mappingFile.exists()) {
def mappingFilename = "$archivesBaseName-$variant.baseName-mapping.txt"
(new File(variant.mappingFile.parent, mappingFilename)).delete()
variant.mappingFile.renameTo(variant.mappingFile.parent +
"/" + mappingFilename)
}
}
}

Pinhassi's solution above works great and it is conforms to the latest Gradle changes. There are a couple of things though that I had to change:
The module name is hardcoded ("app"), which is not ideal since in a lot of cases (including mine) that will not be true. It is better to dynamically detect the module name.
The mapping file also only conforms to the Windows file system by having backward escaped slashes ("\"). If you are on a *NIX system like Linux or Mac, you need to replace those with forward non escaped slashes ("/")
Changed a bit the renaming of the .apk file to include the project name and added a date/time stamp at the end.
Here is the finished code:
import java.util.regex.Matcher
import java.util.regex.Pattern
buildTypes {
release {
debuggable false
minifyEnabled true
proguardFiles 'proguard.cfg'
// Rename the apk file and copy the ProGuard mapping file to the root of the project
applicationVariants.all { variant ->
if (variant.getBuildType().name.equals("release")) {
def formattedDate = new Date().format('yyyyMMddHHmmss')
def projectName = ""
variant.outputs.each { output ->
def fullName = output.outputFile.name
projectName = fullName.substring(0, fullName.indexOf('-'))
// ${variant.name} has the value of "paidRelease"
output.outputFile = new File((String) output.outputFile.parent, (String) output.outputFile.name.replace(".apk", "-v${variant.versionName}-${formattedDate}.apk"))
}
def mappingFile = "${rootDir}/${projectName}/build/outputs/mapping/${getCurrentFlavor()}/release/mapping.txt"
println("mappingFile: ${mappingFile}")
if (variant.getBuildType().isMinifyEnabled()) {
variant.assemble.doLast {
copy {
from "${mappingFile}"
into "${rootDir}"
rename { String fileName ->
"mapping-${variant.name}.txt"
}
}
}
}
}
}
}
debug {
debuggable true
}
}
def getCurrentFlavor() {
Gradle gradle = getGradle()
String tskReqStr = gradle.getStartParameter().getTaskRequests().toString()
Pattern pattern;
if( tskReqStr.contains( "assemble" ) )
pattern = Pattern.compile("assemble(\\w+)(Release|Debug)")
else
pattern = Pattern.compile("generate(\\w+)(Release|Debug)")
Matcher matcher = pattern.matcher( tskReqStr )
if( matcher.find() )
return matcher.group(1).toLowerCase()
else {
println "NO MATCH FOUND"
return "";
}
}

applicationVariants.all { variant ->
variant.outputs.each { output ->
if (variant.getBuildType().isMinifyEnabled()) {
variant.assemble.doLast{
copy {
from variant.mappingFile
into "${rootDir}/mapping"
rename { String fileName ->
"mapping-${variant.name}-${new Date().format('yyyy_MM_dd')}.txt"
}
}
}
}
}
}

Here is solution that helps me:
compileSdkVersion 30
JavaVersion.VERSION_1_8
kotlin_version = '1.5.31'
com.android.tools.build:gradle:7.0.2
buildTypes {
release {
minifyEnabled true
shrinkResources true
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
applicationVariants.all { variant ->
// Generating apk file for each flavour release build
variant.outputs.all {
outputFileName = "${variant.flavorName}-${variant.versionCode}.apk"
}
// Generating mapping file for each flavour release build
if (variant.getBuildType().isMinifyEnabled()) {
variant.assembleProvider.get().doLast {
def files = variant.getMappingFileProvider().get().getFiles()
for (file in files) {
if (file != null && file.exists()) {
def newName = "mapping-${variant.flavorName}-${variant.versionCode}.txt"
def newFile = new File(file.parent, newName)
newFile.delete()
file.renameTo(newName)
}
}
}
}
}
}

Could not find property 'outputFile' on com.android.build.gradle.internal.api.ApplicationVariantImpl

After updating to AS 1.0 RC 1 and plugin 0.14.4 I am having problems with the renaming part of my build.gradle:
applicationVariants.all { variant ->
def file = variant.outputFile
variant.outputFile = new File(file.parent, file.name.replace(".apk", "-" + defaultConfig.versionName + ".apk"))
}
throws now:
Error:(78, 0) Could not find property 'outputFile' on com.android.build.gradle.internal.api.ApplicationVariantImpl_Decorated#67e7625f.
and also I cannot jump to the class ApplicationVariantImpl to look how the property might have been renamed.
Anyone knows workarounds for this?

try this
applicationVariants.all { variant ->
variant.outputs.each { output ->
def file = output.outputFile
output.outputFile = new File(file.parent, file.name.replace(".apk", "-" + defaultConfig.versionName + ".apk"))
}
}

More comprehensively:
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File(output.outputFile.parent, output.outputFile.name.replace(".apk", "-" + defaultConfig.versionName + ".apk"))
}
}

This can occur for few reasons:
1.) First as was said before by #Khalidov, try
applicationVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = ...
}
}
2.) Second try update all other plugins.
For example I got this problem for Spoon, that resolved by update Spoon up to:
classpath 'com.stanfy.spoon:spoon-gradle-plugin:0.14.1'

Or where there's only one variant:
def apk = outputs[0].outputFile
Instead of
def apk = variant.outputFile

Make sure you run the latest gradle version (not the plugin, gradle it self).
Check your gradle-wrapper.properties. Are you running gradle 2.1?
More info on compatibility: http://tools.android.com/tech-docs/new-build-system/version-compatibility

I managed to solve as follows:
old:
buildTypes {
libertação {
runProguard false // esta linha tem que ser mudado
proguardFiles getDefaultProguardFile ( 'android.txt proguard-' ), 'proguard-rules.pro'
}
}
new:
buildTypes {
libertação {
minifyEnabled false // nova versão
proguardFiles getDefaultProguardFile ( 'android.txt proguard-' ), 'proguard-rules.pro'
}
}
edited in file buil.gradle of your project as described in this post by ruan65
Error:(26, 0) Gradle DSL method not found: 'runProguard()'
and after edit too this line:
applicationVariants . all { variant ->
variant . outputs . each { output ->
def file = output . outputFile
output . outputFile = new File ( file . parent , file . name . replace ( ".apk" , "-" + defaultConfig . versionName + ".apk" ))
}
}
as it was said up there.
That settled me!

How to set name of AAR output from Gradle

I have a project with several modules in it one of which is a Android Library named (poorly) as sdk. When I build the project it outputs an AAR named sdk.aar.
I haven't been able to find anything in the Android or Gradle documentation that allows me to change the name of the AAR output. I would like it to have a basename + version number like the Jar tasks do, but I can't work out how to do the same for the AAR because all the config for it seems to be hidden in the android.library plugin.
Renaming the module isn't an option at this stage and that still wouldn't add the version number to the final AAR.
How can I change the name of the AAR generated by com.android.library in Gradle?
Gradle solution
defaultConfig {
minSdkVersion 9
targetSdkVersion 19
versionCode 4
versionName '1.3'
testFunctionalTest true
project.archivesBaseName = "Project name"
project.version = android.defaultConfig.versionName
}

As mentioned in comments below and another answer, the original answer here doesn't work with Gradle 3+. Per the docs, something like the following should work:
Using the Variant API to manipulate variant outputs is broken with the
new plugin. It still works for simple tasks, such as changing the APK
name during build time, as shown below:
// If you use each() to iterate through the variant objects,
// you need to start using all(). That's because each() iterates
// through only the objects that already exist during configuration time—
// but those object don't exist at configuration time with the new model.
// However, all() adapts to the new model by picking up object as they are
// added during execution.
android.applicationVariants.all { variant ->
variant.outputs.all {
outputFileName = "${variant.name}-${variant.versionName}.apk"
}
}
OLD ANSWER:
I am unable to get archivesBaseName & version to work for me w/ Android Studio 0.8.13 / Gradle 2.1. While I can set archivesBaseName and version in my defaultConfig, it doesn't seem to affect the output name. In the end, adding the following libraryVariants block to my android {} scope finally worked for me:
libraryVariants.all { variant ->
variant.outputs.each { output ->
def outputFile = output.outputFile
if (outputFile != null && outputFile.name.endsWith('.aar')) {
def fileName = "${archivesBaseName}-${version}.aar"
output.outputFile = new File(outputFile.parent, fileName)
}
}
}

For Android Studio 3 with Gradle 4 and Android Plugin for Gradle 3.0.0 you have to change the answer of qix to the following:
android {
...
libraryVariants.all { variant ->
variant.outputs.all { output ->
if (outputFile != null && outputFileName.endsWith('.aar')) {
outputFileName = "${archivesBaseName}-${version}.aar"
}
}
}
}

In my case, ${version} result in "unspecified", finnally I found ${defaultConfig.versionName} works.
android {
...
libraryVariants.all { variant ->
variant.outputs.all {
outputFileName = "${variant.name}-${defaultConfig.versionName}.aar"
}
}
}

with the build-plugin 1.5.0 it is now possible to use archivesBaseName in the defaultConfig

For the latest version of Gradle 5+, this is the best answer following #frouo answer:
defaultConfig {
...
versionName "some-version-name-or-number"
setProperty("archivesBaseName", "${archivesBaseName}-$versionName")
...
}
AAR extension will be added automatically.

In addition to qix answer here the info that you can add multiple output paths by this method by an regular string as well:
libraryVariants.all { variant ->
variant.outputs.each { output ->
def outputFile = output.outputFile
if (outputFile != null && outputFile.name.endsWith('.aar')) {
def fileName = "${archivesBaseName}-${version}.aar"
output.outputFile = new File(outputFile.parent, fileName)
output.outputFile = new File("/home/pepperonas/IdeaProjects/Libraries/Base/testapp/libs", fileName)
}
}
}
(Upvotes belong to qix - I just wrote this as an answer because of the readability).

Using Gradle 6+ and AGP 4+, an alternative answer that allows full control of the name is:
afterEvaluate {
android.libraryVariants.all { variant ->
variant.variantData.outputFactory.apkDataList.each { apkData ->
if (apkData.outputFileName.endsWith('.aar')) {
apkData.outputFileName = "${project.name}-${buildType.name}-anything-you-want.aar"
}
}
}
}

For Gradle 5+:
android.libraryVariants.all { variant ->
variant.variantData.outputFactory.output.apkDatas.each { apkData ->
apkData.outputFileName = "YourNewFileName.aar"
}
}
For Gradle 4+:
android.libraryVariants.all { variant ->
variant.outputs.each { output ->
output.outputFileName = "YourNewFileName.aar"
}
}
For Gradle 2+ and Gradle 3+:
android.libraryVariants.all { variant ->
variant.outputs.each { output ->
output.outputFile = new File(file.parent, "YourNewFileName.aar")
}
}