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About David Wong

David is a software developer who has worked in the UK, Japan and Australia. He likes building apps in Java, web and Android technologies.

Avoid Gradle Duplication in Multi-Module Android

When you have an Android project with many modules, you may find a lot of the gradle configuration being duplicated (often by copy and paste) across the build.gradle files in the various modules.

I’ve read various ways to try to avoid this on the internet, and came across this blog post recently. This post uses the name of the module to determine which gradle plugins to apply and which configuration to use for that module.

In one of my multiple module projects, I have used something similar. However the difference is that I apply the plugins required in each individual module build.gradle, and in the root build.config I use both the module name and it’s properties to add the appropriate shared configuration.

For example, here is the common shared configuration for all modules in the root build.gradle:

subprojects {
    afterEvaluate { project ->
        if (project.hasProperty("android")) {
            android {
                compileSdkVersion 30
                buildToolsVersion '30.0.2'
                defaultConfig {
                    minSdkVersion 23
                    targetSdkVersion 30
                }
                compileOptions {
                    sourceCompatibility JavaVersion.VERSION_11
                    targetCompatibility JavaVersion.VERSION_11
                }
            }
        }
}

This app is a mixed Java and Kotlin project so only some of the modules use Kotlin. In the Kotlin modules, I apply the kotlin plugin.

apply plugin: 'com.android.library'
apply plugin: 'kotlin-android'

Then in the root build.gradle, I can add the Kotlin configurations to those modules:

if (project.hasProperty('kotlin')) {
        android {
            kotlinOptions {
                jvmTarget = JavaVersion.VERSION_11.toString()
            }
        }
        dependencies {
            implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
            implementation 'androidx.core:core-ktx'
        }
}

If there is common configuration that is only applicable to some modules, I can also use the module name as a filter to add that configuration for only those modules. For instance for all modules excluding the app module:

if (project.hasProperty('android') && !name.equalsIgnoreCase('app')) {
      ...
}

Likewise for modules with particular names:

if (project.hasProperty('android') && name.equalsIgnoreCase('feature-1')) {
      ...
}

Note that I use the root build.gradle to contain the common configuration to keep things simple, but there are also more complicated methods around that use the buildSrc directory instead.

Published on Java Code Geeks with permission by David Wong, partner at our JCG program. See the original article here: Avoid Gradle Duplication in Multi-Module Android

Opinions expressed by Java Code Geeks contributors are their own.

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