Develop Reference

CacheOpenException when trying to migrate Android Gradle project from Groovy to Kotlin

So I'm trying to migrate my build.gradle files in a simple toy app from Groovy to the new Kotlin dsl for Gradle. I have been able to successfully migrate my project build.gradle file and I've also created a buildSrc directory that has all the version numbers and such in a Kotlin files. So far gradle was syncing and building successfully. But then when I tried to convert my app build.gradle to Kotlin (by changing the file extension and changing all the function calls and maps and such to follow the Kotlin syntax) I got an error in my gradle sync that says:
org.gradle.internal.exceptions.LocationAwareException: A problem occurred configuring project ':app'.
Caused by: org.gradle.api.ProjectConfigurationException: A problem occurred configuring project ':app'.
Caused by: org.gradle.cache.CacheOpenException: Could not open cache directory er2fj44y4paf4xwhwuc5jhit0 (C:\Users\Youssef Shoaib\.gradle\caches\5.6.4\gradle-kotlin-dsl-accessors\er2fj44y4paf4xwhwuc5jhit0).
Caused by: java.util.zip.ZipException: zip file is empty
I've tried rebuilding and cleaning the build but it still doesn't work. When I change my app build.gradle back to groovy the error disappears and everything works, but I really wanna use the Kotlin DSL for Gradle. I've also tried changing my Kotlin version and my Gradle version but it still didn't work.
For reference, here's my buildSrc build.gradle.kts
plugins {
`kotlin-dsl`
}
repositories {
jcenter()
}
and my Dependencies.kt inside the buildSrc module:
object Versions {
const val version_core = "1.1.0"
const val version_coroutine = "1.1.1"
const val version_constraint_layout = "1.1.3"
const val version_gradle = "3.5.3"
const val version_kotlin = "1.3.61"
const val version_lifecycle_extensions = "2.1.0"
const val version_navigation = "2.1.0"
const val version_room = "2.2.2"
}
and my project build.gradle.kts file:
buildscript {
repositories {
google()
jcenter()
}
dependencies {
classpath("com.android.tools.build:gradle:${Versions.version_gradle}")
classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:${Versions.version_kotlin}")
classpath("androidx.navigation:navigation-safe-args-gradle-plugin:${Versions.version_navigation}")
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
}
allprojects {
repositories {
google()
jcenter()
}
}
tasks.register<Delete>("clean") {
delete(rootProject.buildDir)
}
And my app build.gradle.kts file:
plugins{
id("com.android.application")
kotlin("android")
kotlin("android.extensions")
kotlin("kapt")
id("androidx.navigation.safeargs.kotlin")
}
android {
compileOptions {
sourceCompatibility( JavaVersion.VERSION_1_8)
targetCompatibility( JavaVersion.VERSION_1_8)
}
kotlinOptions {
jvmTarget("1.8")
}
compileSdkVersion(29)
defaultConfig {
applicationId = "com.example.android.trackmysleepquality"
minSdkVersion(19)
targetSdkVersion(29)
versionCode = 1
versionName = "1.0"
testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
vectorDrawables.useSupportLibrary = true
javaCompileOptions {
annotationProcessorOptions {
arguments = mapOf("room.incremental" to "true")
}
}
}
buildTypes {
getByName("release") {
isMinifyEnabled = false
proguardFiles(getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro")
}
}
// Enables data binding.
dataBinding {
enabled = true
}
}
dependencies {
implementation(fileTree(mapOf("dir" to "libs"), "include:" to listOf("*.jar")))
implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk7:${Versions.version_kotlin}")
// Support libraries
implementation("androidx.constraintlayout:constraintlayout:${Versions.version_constraint_layout}")
// Android KTX
implementation("androidx.core:core-ktx:${Versions.version_core}")
// Room and Lifecycle dependencies
implementation("androidx.room:room-runtime:${Versions.version_room}")
implementation("androidx.room:room-ktx:${Versions.version_room}")
kapt("androidx.room:room-compiler:${Versions.version_room}")
implementation("androidx.lifecycle:lifecycle-extensions:${Versions.version_lifecycle_extensions}")
implementation("com.github.hadilq.liveevent:liveevent:1.0.1")
// Coroutines
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:${Versions.version_coroutine}")
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:${Versions.version_coroutine}")
// Navigation
implementation("androidx.navigation:navigation-fragment-ktx:${Versions.version_navigation}")
implementation("androidx.navigation:navigation-ui-ktx:${Versions.version_navigation}")
// Testing
testImplementation("junit:junit:4.12")
androidTestImplementation("androidx.test.ext:junit:1.1.1")
androidTestImplementation("androidx.arch.core:core-testing:2.1.0")
androidTestImplementation("androidx.test.espresso:espresso-core:3.2.0")
androidTestImplementation("org.mockito:mockito-core:3.1.0")
}

I finally found a solution. I just deleted the whole .gradle directory inside my user folder, which, I think, invalidated all the caches that Android Studio might have made for the accessors for the Kotlin dsl. So, in the end, it does actually work

Build jitpack library with multi flavor in Android

I am using Gradle 4.1 with Gradle-Android plugin 3.0.1 on Android Studio 3.2
I have 2 flavors 'production' and 'staging' and I am unable to build my project as a library with different build variants.
app build.gradle:
apply plugin: 'com.android.library'
apply plugin: 'com.github.dcendents.android-maven'
android {
...
productFlavors {
production {
}
staging {
}
}
defaultPublishConfig "productionRelease"
publishNonDefault true
}
if( android.productFlavors.size() > 0 ) {
android.libraryVariants.all { variant ->
if( android.publishNonDefault && variant.name == android.defaultPublishConfig ) {
def bundleTask = tasks["bundle${name.capitalize()}"]
artifacts {
archives(bundleTask.archivePath) {
classifier name.replace('-' + variant.name, '')
builtBy bundleTask
name name.replace('-' + variant.name, '')
}
}
}
...
Then I run: ./gradlew clean install, errors I got is:
Execution failed for task ‘:app:install’.
Could not publish configuration ‘archives’
A POM cannot have multiple artifacts with the same type and classifier. Already have MavenArtifact app:aar:aar:null, trying to add MavenArtifact app:aar:aar:null.
And to get this code to compile, I need to swap android.publishNonDefault with true, otherwise I will get an error of: Cannot get the value of write-only property 'publishNonDefault'
Any suggestions or hint would be really helpful, the aim is to build the library module on jitpack, where we can import it in project with build variants. thanks!

After digging into this for 2 days, and emailing Jitpack support, the issue is because the lib has updated and publishNonDefault is deprecated. you just need to change your app build.gradle to:
apply plugin: 'com.github.dcendents.android-maven'
dependencies {...}
group = 'com.github.your-group'
if (android.productFlavors.size() > 0) {
android.libraryVariants.all { variant ->
if (variant.name.toLowerCase().contains("debug")) {
return
}
def bundleTask = tasks["bundle${variant.name.capitalize()}"]
artifacts {
archives(bundleTask.archivePath) {
classifier variant.flavorName
builtBy bundleTask
name = project.name
}
}
}
}

problem was to create multiple flavors using jitpack
so what I do is, create a variable which stores the flavor name, after that loop through the available variant, pass the flavorBuild to artifact so when u push the code to GitHub and create artifact via jitpack then jitpack create the required implementation based on your build flavor and then u can use it. You need to just change build flavor
publishing {
publications {
def flavorBuild ='production'
android.libraryVariants.all { variant ->
"maven${variant.name.capitalize()}Aar"(MavenPublication) {
from components.findByName("android${variant.name.capitalize()}")
groupId = 'com.examplesdk'
artifactId = 'examplesdk'
version "1.0.0-${variant.name}"
artifact "$buildDir/outputs/aar/examplesdk-${flavorBuild}-release.aar"
pom.withXml {
def dependenciesNode = asNode().appendNode('dependencies')
configurations.api.allDependencies.each { dependency ->
def dependencyNode = dependenciesNode.appendNode('dependency')
dependencyNode.appendNode('groupId', dependency.group)
dependencyNode.appendNode('artifactId', dependency.name)
dependencyNode.appendNode('version', dependency.version)
}
}
}
}
}
repositories{
maven {
url "$buildDir/repo"
}
}
}

Findbugs in Gradle build fails after upgrading to Android Gradle Plugin 3.2

Error message:
No files to be analyzed
My findbugs configuration is like:
tasks.create([ "type" : FindBugs, "dependsOn" : "assemble", "group": "verification", "name": "findbugs"]) {
classes = files("$projectDir.absolutePath/build/intermediates/classes")
source = fileTree('src/main/java')
classpath = files()
}

Seems like the class path have changed in AGP 3.2 from build/intermediates/classes to build/intermediates/javac.

task findbugs(type: FindBugs) {
ignoreFailures = true
classes = files("${project.rootDir}/app/build/intermediates/javac",
"${project.rootDir}/database/build/intermediates/javac",
"${project.rootDir}/dataprovider/build/intermediates/javac")
source = fileTree('app/src/main/java/')
classpath = files()
reports {
html.enabled = true
xml.enabled = false
}
}

Just change the classes path in file findbugs.gradle from classes = fileTree("$project.buildDir/intermediates/classes/dev/debug/com/android"
to classes = fileTree("$project.buildDir/intermediates/javac/debug/compileDebugJavaWithJavac/classes/android".

Publishing Android Library (aar) to Bintray with chosen flavors

I've juste added some flavors (or productFlavors if you want) to my project.
The fact is that when I publish the library to bintray, all flavors are uploaded (which is great), but I'm unable to use them. The plugin used is the official one here.
The uploaded aar:
androidsdk-0.0.4-fullRelease.aar
androidsdk-0.0.4-fullDebug.aar
androidsdk-0.0.4-lightRelease.aar
androidsdk-0.0.4-lightDebug.aar
As you noted, the fullRelease is named as the classifier, see doc chapter 23.4.1.3.
I am searching for a solution to choose which flavors that I want to upload.
I've already looked at bintray examples (here and here) and this, with also other examples but I'm still stuck.
Here is my current script:
apply plugin: 'com.android.library'
apply plugin: 'com.github.dcendents.android-maven'
apply plugin: 'com.jfrog.bintray'
buildscript {
repositories {
jcenter()
}
}
android {
compileSdkVersion 23
buildToolsVersion "23.0.1"
defaultConfig {
minSdkVersion 9
targetSdkVersion 23
versionCode 64
versionName "0.0.4"
}
publishNonDefault true
productFlavors {
full {
}
light {
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:23.1.1'
compile 'com.android.support:recyclerview-v7:23.1.1'
fullCompile 'com.squareup.picasso:picasso:2.5.0'
}
version = android.defaultConfig.versionName
uploadArchives {
repositories.mavenDeployer {
pom.project {
packaging 'aar'
}
}
}
////////////////////////////////
// Bintray Upload configuration
Properties properties = new Properties()
properties.load(project.rootProject.file('local.properties').newDataInputStream())
bintray {
user = properties.getProperty("bintray.user")
key = properties.getProperty("bintray.apikey")
configurations = ['archives']
pkg {
repo = "MyRepo" // repo name
userOrg = 'hugo'
name = "AndroidSDK" // Package name
websiteUrl = siteUrl
vcsUrl = gitUrl
publish = true
}
}
To import the library I'm currently using this:
compile ('com.example.lib:sdk:0.0.8:fullRelease#aar') {
transitive = true;
}

I faced the same challenge, and here's the best I could make yet:
Using mavenPublications and the gradle maven-publish plugin along the bintray plugin, you can publish any variant to mavenLocal and bintray.
Here's the publish.gradle file I apply at the end of all my project's library modules I want to publish:
def pomConfig = {
licenses {
license {
name 'The Apache Software License, Version 2.0'
url 'http://www.apache.org/licenses/LICENSE-2.0.txt'
}
}
developers {
developer {
id 'louiscad'
name 'Louis CAD'
email 'louis.cognault#gmail.com'
}
}
scm {
connection 'https://github.com/LouisCAD/Splitties.git'
developerConnection 'https://github.com/LouisCAD/Splitties.git'
url siteUrl
}
}
def publicationNames = []
publishing.publications {
android.libraryVariants.all { variant ->
if (variant.buildType.name == "debug") return // Prevents publishing debug library
def flavored = !variant.flavorName.isEmpty()
/**
* Translates "_" in flavor names to "-" for artifactIds, because "-" in flavor name is an
* illegal character, but is well used in artifactId names.
*/
def variantArtifactId = flavored ? variant.flavorName.replace('_', '-') : project.name
/**
* If the javadoc destinationDir wasn't changed per flavor, the libraryVariants would
* overwrite the javaDoc as all variants would write in the same directory
* before the last javadoc jar would have been built, which would cause the last javadoc
* jar to include classes from other flavors that it doesn't include.
*
* Yes, tricky.
*
* Note that "${buildDir}/docs/javadoc" is the default javadoc destinationDir.
*/
def javaDocDestDir = file("${buildDir}/docs/javadoc ${flavored ? variantArtifactId : ""}")
/**
* Includes
*/
def sourceDirs = variant.sourceSets.collect {
it.javaDirectories // Also includes kotlin sources if any.
}
def javadoc = task("${variant.name}Javadoc", type: Javadoc) {
description "Generates Javadoc for ${variant.name}."
source = variant.javaCompile.source // Yes, javaCompile is deprecated,
// but I didn't find any working alternative. Please, tweet #Louis_CAD if you find one.
destinationDir = javaDocDestDir
classpath += files(android.getBootClasspath().join(File.pathSeparator))
classpath += files(configurations.compile)
options.links("http://docs.oracle.com/javase/7/docs/api/");
options.links("http://d.android.com/reference/");
exclude '**/BuildConfig.java'
exclude '**/R.java'
failOnError false
}
def javadocJar = task("${variant.name}JavadocJar", type: Jar, dependsOn: javadoc) {
description "Puts Javadoc for ${variant.name} in a jar."
classifier = 'javadoc'
from javadoc.destinationDir
}
def sourcesJar = task("${variant.name}SourcesJar", type: Jar) {
description "Puts sources for ${variant.name} in a jar."
from sourceDirs
classifier = 'sources'
}
def publicationName = "splitties${variant.name.capitalize()}Library"
publicationNames.add(publicationName)
"$publicationName"(MavenPublication) {
artifactId variantArtifactId
group groupId
version libraryVersion
artifact variant.outputs[0].packageLibrary // This is the aar library
artifact sourcesJar
artifact javadocJar
pom {
packaging 'aar'
withXml {
def root = asNode()
root.appendNode("name", 'Splitties')
root.appendNode("url", siteUrl)
root.children().last() + pomConfig
def depsNode = root["dependencies"][0] ?: root.appendNode("dependencies")
def addDep = {
if (it.group == null) return // Avoid empty dependency nodes
def dependencyNode = depsNode.appendNode('dependency')
dependencyNode.appendNode('groupId', it.group)
dependencyNode.appendNode('artifactId', it.name)
dependencyNode.appendNode('version', it.version)
if (it.hasProperty('optional') && it.optional) {
dependencyNode.appendNode('optional', 'true')
}
}
// Add deps that everyone has
configurations.compile.allDependencies.each addDep
// Add flavor specific deps
if (flavored) {
configurations["${variant.flavorName}Compile"].allDependencies.each addDep
}
// NOTE: This library doesn't use builtTypes specific dependencies, so no need to add them.
}
}
}
}
}
group = groupId
version = libraryVersion
afterEvaluate {
bintray {
user = bintray_user
key = bintray_api_key
publications = publicationNames
override = true
pkg {
repo = 'splitties'
name = project.name
desc = libraryDesc
websiteUrl = siteUrl
issueTrackerUrl = 'https://github.com/LouisCAD/Splitties/issues'
vcsUrl = gitUrl
licenses = ['Apache-2.0']
labels = ['aar', 'android']
publicDownloadNumbers = true
githubRepo = 'LouisCAD/Splitties'
}
}
}
In order for this to work, I need to have the bintray_user and bintray_api_key properties defined. I personally just have them in my ~/.gradle/gradle.properties file like this:
bintray_user=my_bintray_user_name
bintray_api_key=my_private_bintray_api_key
I also need to define the following ext properties I used in the publish.gradle file in my root project's build.gradle file:
allprojects {
...
ext {
...
// Libraries
groupId = "xyz.louiscad.splitties"
libraryVersion = "1.2.1"
siteUrl = 'https://github.com/LouisCAD/Splitties'
gitUrl = 'https://github.com/LouisCAD/Splitties.git'
}
}
And now, I can finally use it in my android library module, where I have multiple productFlavors. Here's a snippet from a publishable library module's build.gradle file:
plugins {
id "com.jfrog.bintray" version "1.7.3" // Enables publishing to bintray
id "com.github.dcendents.android-maven" version "1.5" // Allows aar in mavenPublications
}
apply plugin: 'com.android.library'
apply plugin: 'maven-publish' // Used for mavenPublications
android {
...
defaultPublishConfig "myLibraryDebug" // Allows using this library in another
// module in this project without publishing to mavenLocal or Bintray.
// Useful for debug purposes, or for your library's sample app.
defaultConfig {
...
versionName libraryVersion
...
}
...
productFlavors {
myLibrary
myLibrary_logged // Here, the "_" will be replaced "-" in artifactId when publishing.
myOtherLibraryFlavor
}
...
}
dependencies {
...
// Timber, a log utility.
myLibrary_loggedCompile "com.jakewharton.timber:timber:${timberVersion}"; // Just an example
}
...
ext {
libraryDesc = "Delegates for kotlin on android that check UI thread"
}
apply from: '../publish.gradle' // Makes this library publishable
When you have all of this setup properly, with the name of your library instead of mine's (which you can use as an example), you can try publishing a version of your flavored library by trying to first publishing to mavenLocal.
To do so, run this command:
myLibrary $ ../gradlew publishToMavenLocal
You can then try adding mavenLocal in your app's repositories (example here) and try adding your library as a dependency (artifactId should be the flavor name, with "_" replaced with "-") and building it.
You can also check with your file explorer (use cmd+shift+G on Mac in Finder to access hidden folder) the directory ~/.m2 and look for your library.
When it's time to publish to bintray/jcenter, you just have to run this command:
myLibrary $ ../gradlew bintrayUpload
Important:
Before you publish your library to mavenLocal, Bintray or another maven repository, you'll usually want to try your library against a sample app which uses the library. This sample app, which should be another module in the same project just need to have the project dependency, which should look like this: compile project(':myLibrary'). However, since your library has multiple productFlavors, you'll want to test all of them. Unfortunately, it's currently impossible to specify which configuration you want to use from your sample app's build.gradle file (unless, you use publishNonDefault true in your library's build.gradle file, which breaks maven and bintray publications), but you can specify the default configuration (i.e. buildVariant) in your library's module as such: defaultPublishConfig "myLibraryDebug" in the android closure. You can see the available build variants for your library in the "Build Variants" tool Windows in Android Studio.
Feel free to explore my library "Splitties" here if you need an example. The flavored module is named concurrency, but I use my script for unflavored library modules too, and I tested it throughly on all the library modules in my project.
You can reach me out if you need help setting it up for you.

The setup:
buildTypes {
debug {
}
release {
}
}
publishNonDefault true
The fix:
defaultPublishConfig 'release'
// Fix for defaultPublishConfig not working as expected
// ref: https://github.com/dcendents/android-maven-gradle-plugin/issues/11
libraryVariants.all { variant ->
if( publishNonDefault && variant.name == defaultPublishConfig ) {
def bundleTask = tasks["bundle${variant.name.capitalize()}"]
artifacts {
archives(bundleTask.archivePath) {
classifier null //necessary to get rid of the suffix in the artifact
builtBy bundleTask
name name.replace('-' + variant.name, '')//necessary to get rid of the suffix from the folder name
}
}
}
}
This fix will still publish all the artifacts, but it will publish a default artifact without the flavour suffix, which is enough to make it all work.
The fix to upload only the default artifact would be this (if the bintray plugin knew what POM filters are):
install {
repositories.mavenInstaller {
/*
POM filters can be used to block artifacts from certain build variants.
However, Bintray does not respect POM filters, therefore this only works for maven deploy plugin.
Also, bintray crashes with named filters, since it always expects a /build/pom/pom-default.xml,
which does not happen with named filters.
*/
filter { artifact, file ->
// this how the default classifier is identified in case the defaultPublishConfig fix is applied
artifact.attributes.classifier == null
}
}
}

I didn't try it so I will delete the answer if it doesn't resolve the issue.
You should post a different artifact for each flavor (or build variant if you prefer).
In this way you will have in jcenter x artifacts, each of them with a pom file.
Something like:
groupId
|--library-full
|----.pom
|----.aar
|--library-light
|----.pom
|----.aar
In your top level file you can define
allprojects {
repositories {
jcenter()
}
project.ext {
groupId="xxx"
libraryName = ""
......
}
}
Then in your library module:
productFlavors {
full {
project.ext.set("libraryName", "library-full");
}
light {
project.ext.set("libraryName", "library-light");
}
}
bintray {
//...
pkg {
//...Do the same for other variables
name = project.ext.libraryName
}
}
Finally make sure to publish only the release build type (why also the debug version?)

If someone is still stuck with this problem here's what worked for me -
Let's say you want to publish the release build for your flavour1 add this to your build.gradle
android {
...
defaultPublishConfig "flavour1Release"
}
Remove publishNonDefault true if it is present in your gradle file.
Add this inside the bintray block like this
bintray {
...
archivesBaseName = 'YOUR_ARTIFACT_ID'
...
}
Then just run the bintrayUpload task as you would.
The defaultPublishConfig will have to be changed everytime you need to publish a new flavour.

It sounds like you don't want the classifier in the filename. It looks like the classifier is the same as the generated library file name. Have you tried giving them the same filename but outputting them to separate directories?
E.g. in the android scope:
libraryVariants.all { variant ->
variant.outputs.each { output ->
def outputFile = output.outputFile
if (outputFile != null && outputFile.name.endsWith('.aar')) {
def fileName = "same_name-${version}.aar"
output.outputFile = new File(outputFile.parent+"/${archivesBaseName}", fileName)
}
}
}

FindBugs Android Gradle No classes configured error

I am trying to use the FindBugs plugin for Gradle with an Android build.
The build.gradle file
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath 'com.android.tools.build:gradle:0.6.+'
}
}
apply plugin: 'android'
apply plugin: 'findbugs'
android {
compileSdkVersion 19
buildToolsVersion "19.0.0"
defaultConfig {
minSdkVersion 8
targetSdkVersion 19
}
}
dependencies {
compile 'com.android.support:appcompat-v7:+'
}
But when I execute the check task it says
No classes configured for FindBugs analysis.
How do I configure classes for FindBugs analysis?

This is not possible at the moment as findbugs expect Gradle's normal Java SourceSets but the android plugin uses custom ones.
There's work planned in both Gradle and in the Android plugin to allow using the default SourceSets which will enable FindBugs.
You track this issue here: https://code.google.com/p/android/issues/detail?id=55839

In newer versions of Android Studio this problem could be attributed to the fact that the location of the classes directory has changed.
The new location (as of 0.8.2) is:
build/intermediates/classes/{build_variant_name}/
for example
build/intermediates/classes/debug/
task findbugs(type: FindBugs) {
excludeFilter = file('config/findbugs/findbugs.xml')
ignoreFailures = true
classes = fileTree('build/intermediates/classes/preproduction/')
source = fileTree('src/main/java/')
classpath = files()
effort = 'max'
reports {
xml {
destination "reports/findbugs.xml"
}
}
}

This is definitely possible. At least now.
The answer can be seen on https://gist.github.com/rciovati/8461832 at the bottom.
apply plugin: 'findbugs'
// android configuration
findbugs {
sourceSets = []
ignoreFailures = true
}
task findbugs(type: FindBugs, dependsOn: assembleDebug) {
description 'Run findbugs'
group 'verification'
classes = fileTree('build/intermediates/classes/debug/')
source = fileTree('src/main/java')
classpath = files()
effort = 'max'
excludeFilter = file("../config/findbugs/exclude.xml")
reports {
xml.enabled = true
html.enabled = false
}
}
check.doLast {
project.tasks.getByName("findbugs").execute()
}
The important part here is dependsOn: assembleDebug.
Without that you will get a No classes configured for FindBugs analysis error message.
Refer to this https://stackoverflow.com/a/7743935/1159930 for the exclude file.

I was able to solving the problem
by adding find bug as separate task
task findbugs(type: FindBugs) {
ignoreFailures = true
classes = fileTree('build/classes/debug/')
source = fileTree('src/main/java/')
classpath = files()
effort = 'max'
}
this task can run using
gradle findbugs
If you are using android-test plugin you have to exclude findbugsTestDebug task when build.
gradle build -x findbugsTestDebug

I have to specify the default sourceSet for findbugs. Initially it wasnt there so I was getting the error.
findbugs {
sourceSets = [] //Default sourceSet
toolVersion = "3.0.1"
ignoreFailures = true
reportsDir = file("$project.buildDir/findbugsReports")
effort = "max"
reportLevel = "low"
}

As other people wrote, you have to set sourceSets, i.e.:
task findbugs(type: FindBugs) {
// ignoreFailures = false
ignoreFailures = true
effort = 'max'
reportLevel = 'low'
excludeFilter = file("quality/findbugs/findbugs-filter.xml")
classes = files("${project.buildDir}/intermediates/javac/debug/classes",
source "${file(getProjectDir().getPath()).getAbsolutePath()}/src"
include '**/*.java'
exclude "${project.buildDir}/generated/**/*.java"
reports {
xml.enabled = true
xml {
destination file("findbugs/report.xml")
}
/*
html.enabled = true
html {
destination file("findbugs/report.html")
}
*/
/*
text.enabled = true
text {
destination file("findbugs/report.txt")
}
*/
}
classpath = files()
}
The problem is that when you upgrade version of Android Gradle Plugin, this path changes now and then.
In our project in different times it was of following values:
"${project.buildDir}/intermediates/classes/debug"
"${project.buildDir}/intermediates/javac/debug/compileDebugJavaWithJavac/classes"
"${project.buildDir}/intermediates/javac/debug/classes"
So if none of mentioned above values worked out, try to find actual classes in your build tree, maybe they just changed it again.