How to autoincrement versionCode in Android Gradle

I have decided for second option - to parse AndroidManifest.xml. Here is working snippet.

task('increaseVersionCode') << {
    def manifestFile = file("AndroidManifest.xml")
    def pattern = Pattern.compile("versionCode=\"(\\d+)\"")
    def manifestText = manifestFile.getText()
    def matcher = pattern.matcher(manifestText)
    matcher.find()
    def versionCode = Integer.parseInt(matcher.group(1))
    def manifestContent = matcher.replaceAll("versionCode=\"" + ++versionCode + "\"")
    manifestFile.write(manifestContent)
}

tasks.whenTaskAdded { task ->
    if (task.name == 'generateReleaseBuildConfig') {
        task.dependsOn 'increaseVersionCode'
    }
}

versionCode is released for release builds in this case. To increase it for debug builds change task.name equation in task.whenTaskAdded callback.

I'm using this code to update both versionCode and versionName, using a "major.minor.patch.build" scheme.

import java.util.regex.Pattern

task('increaseVersionCode') << {
    def manifestFile = file("src/main/AndroidManifest.xml")
    def pattern = Pattern.compile("versionCode=\"(\\d+)\"")
    def manifestText = manifestFile.getText()
    def matcher = pattern.matcher(manifestText)
    matcher.find()
    def versionCode = Integer.parseInt(matcher.group(1))
    def manifestContent = matcher.replaceAll("versionCode=\"" + ++versionCode + "\"")
    manifestFile.write(manifestContent)
}

task('incrementVersionName') << {
    def manifestFile = file("src/main/AndroidManifest.xml")
    def patternVersionNumber = Pattern.compile("versionName=\"(\\d+)\\.(\\d+)\\.(\\d+)\\.(\\d+)\"")
    def manifestText = manifestFile.getText()
    def matcherVersionNumber = patternVersionNumber.matcher(manifestText)
    matcherVersionNumber.find()
    def majorVersion = Integer.parseInt(matcherVersionNumber.group(1))
    def minorVersion = Integer.parseInt(matcherVersionNumber.group(2))
    def pointVersion = Integer.parseInt(matcherVersionNumber.group(3))
    def buildVersion = Integer.parseInt(matcherVersionNumber.group(4))
    def mNextVersionName = majorVersion + "." + minorVersion + "." + pointVersion + "." + (buildVersion + 1)
    def manifestContent = matcherVersionNumber.replaceAll("versionName=\"" + mNextVersionName + "\"")
    manifestFile.write(manifestContent)
}

tasks.whenTaskAdded { task ->
    if (task.name == 'generateReleaseBuildConfig' || task.name == 'generateDebugBuildConfig') {
        task.dependsOn 'increaseVersionCode'
        task.dependsOn 'incrementVersionName'
    }
}

it doesn't seem to be the exact setup you're using, but in my case the builds are being run by jenkins and i wanted to use its $BUILD_NUMBER as the app's versionCode. the following did the trick for me there.

defaultConfig {
    ...
    versionCode System.getenv("BUILD_NUMBER") as Integer ?: 9999
    ...
}