A Gradle script to automatically publish Android library to maven or sonatype provided your central sync is enabled.

publish.gradle

/*
 * Copyright 2020 Kaustubh Patange
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


/**
   Automatic publishing on MavenCentral/Sonatype with nexus staging provided
   your maven-central sync is enabled.

   Setup Instructions
   ==================

   - Add following properties to your local.properties file.
    --------------------------------------------------------
     signing.keyId= // gpg key id
     signing.password= // gpg key password
     signing.secretKeyRingFile= // gpg file path
     ossrhUsername= // sonatype username
     ossrhPassword= // sonatype password
    --------------------------------------------------------

   - Add following to top level build.gradle file.
    ----------------------------------------------
     apply plugin: 'io.codearte.nexus-staging'
     classpath "io.codearte.gradle.nexus:gradle-nexus-staging-plugin:0.22.0"
    ----------------------------------------------

   - Save this file into your project's root folder as "publish.gradle".
   - To include an Android library, add following snippet to your's
     library build.gradle file, modify it according to your need.
    ----------------------------------------------------------
     apply plugin: 'maven-publish' // add this at top

     // place this all at the end of build.gradle
     ext {
         PUBLISH_GROUP_ID = 'io.github.kaustubhpatange'
         PUBLISH_ARTIFACT_ID = 'hvlog'
         PUBLISH_VERSION = '1.0'

         PUBLISH_DESCRIPTION = 'A simple light-weight logger for Android'
         PUBLISH_URL = 'https://github.com/KaustubhPatange/HVLog'

         LICENSE_NAME = 'The Apache License, Version 2.0'
         LICENSE_URL = 'https://www.apache.org/licenses/LICENSE-2.0.txt'

         DEVELOPER_ID = 'kp2016'
         DEVELOPER_NAME = 'Kaustubh Patange'
         DEVELOPER_EMAIL = 'developerkp16@gmail.com'

         SCM_CONNECTION = 'scm:git:github.com/KaustubhPatange/HVLog.git'
         SCM_DEVELOPER_CONNECTION = 'scm:git:ssh://github.com/KaustubhPatange/HVLog.git'
         SCM_URL = 'https://github.com/KaustubhPatange/HVLog/tree/master'

         NEXUS_STAGING_ID = '12345abcd' // dummy replace with your own.
     }

     apply from: "${rootProject.projectDir}/publish.gradle"
    ----------------------------------------------------------

    - To publish library,
    -------------------------------------------------------
    ./gradlew module-name:publishReleasePublicationToSonatypeRepository
    ./gradlew closeRepository
    ./gradlew releaseRepository
    -------------------------------------------------------
*/

apply plugin: 'maven-publish'
apply plugin: 'signing'

task androidJavadocs(type: Javadoc) {
    source = android.sourceSets.main.java.srcDirs
    classpath += project.files(android.getBootClasspath().join(File.pathSeparator))
    android.libraryVariants.all { variant ->
        if (variant.name == 'release') {
            owner.classpath += variant.javaCompileProvider.get().classpath
        }
    }
    exclude '**/R.html', '**/R.*.html', '**/index.html'
}

task androidJavadocsJar(type: Jar, dependsOn: androidJavadocs) {
    archiveClassifier.set('javadoc')
    from androidJavadocs.destinationDir
}

task androidSourcesJar(type: Jar) {
    archiveClassifier.set('sources')
    from android.sourceSets.main.java.srcDirs
}

ext["signing.keyId"] = ''
ext["signing.password"] = ''
ext["signing.secretKeyRingFile"] = ''
ext["ossrhUsername"] = ''
ext["ossrhPassword"] = ''

File secretPropsFile = project.rootProject.file('local.properties')
if (secretPropsFile.exists()) {
    println "Found secret props file, loading props"
    Properties p = new Properties()
    p.load(new FileInputStream(secretPropsFile))
    p.each { name, value ->
        ext[name] = value
    }
} else {
    println "No props file, loading env vars"
    ext["signing.keyId"] = System.getenv('SIGNING_KEY_ID')
    ext["signing.password"] = System.getenv('SIGNING_PASSWORD')
    ext["signing.secretKeyRingFile"] = System.getenv('SIGNING_SECRET_KEY_RING_FILE')
    ext["ossrhUsername"] = System.getenv('OSSRH_USERNAME')
    ext["ossrhPassword"] = System.getenv('OSSRH_PASSWORD')
}

signing {
    sign publishing.publications
}

nexusStaging {
    packageGroup = PUBLISH_GROUP_ID
    stagingProfileId = NEXUS_STAGING_ID
    username = ossrhUsername
    password = ossrhPassword
}

afterEvaluate {
    publishing {
        publications {
            release(MavenPublication) {
                from components.release
                artifact androidSourcesJar

                groupId = PUBLISH_GROUP_ID
                artifactId = PUBLISH_ARTIFACT_ID
                version = PUBLISH_VERSION

                pom {
                    name = PUBLISH_ARTIFACT_ID
                    description = PUBLISH_DESCRIPTION
                    url = PUBLISH_URL
                    licenses {
                        license {
                            name = LICENSE_NAME
                            url = LICENSE_URL
                        }
                    }
                    developers {
                        developer {
                            id = DEVELOPER_ID
                            name = DEVELOPER_NAME
                            email = DEVELOPER_EMAIL
                        }
                    }
                    // Version control info, if you're using GitHub, follow the format as seen here
                    scm {
                        connection = SCM_CONNECTION
                        developerConnection = SCM_DEVELOPER_CONNECTION
                        url = SCM_URL
                    }
                }
            }
        }
        repositories {
            // The repository to publish to, Sonatype/MavenCentral
            maven {
                // This is an arbitrary name, you may also use "mavencentral" or
                // any other name that's descriptive for you
                name = "sonatype"

                def releasesRepoUrl = "https://oss.sonatype.org/service/local/staging/deploy/maven2/"
                def snapshotsRepoUrl = "https://oss.sonatype.org/content/repositories/snapshots/"
                // You only need this if you want to publish snapshots, otherwise just set the URL
                // to the release repo directly
                url = version.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl

                // The username and password we've fetched earlier
                credentials {
                    username ossrhUsername
                    password ossrhPassword
                }
            }
        }
    }
}