How to define common android properties for all modules using gradle

In large Android projects, multiple modules are typically involved (such as the app module, library module, etc.). To ensure consistency in build configurations across all modules, it is common to leverage Gradle's capabilities to define common properties. This approach simplifies maintenance, reduces code duplication, and ensures that the entire project stays synchronized when updating dependencies or tool versions.

Step 1: Define the Project-Level build.gradle File

First, define common properties in the project-level build.gradle file located at the root directory of the project.

groovy
// Root directory build.gradle file

// Define commonly used version numbers as variables
ext {
    compileSdkVersion = 31
    minSdkVersion = 21
    targetSdkVersion = 31
    versionCode = 1
    versionName = "1.0"

    // Define other common variables
    supportLibVersion = "1.0.0"
}

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

Step 2: Reference These Properties in Module build.gradle Files

Then, in each module's build.gradle file, you can reference the variables defined in the project-level build.gradle.

groovy
// Module build.gradle file

apply plugin: 'com.android.application'

android {
    compileSdkVersion rootProject.ext.compileSdkVersion

    defaultConfig {
        applicationId "com.example.myapp"
        minSdkVersion rootProject.ext.minSdkVersion
        targetSdkVersion rootProject.ext.targetSdkVersion
        versionCode rootProject.ext.versionCode
        versionName rootProject.ext.versionName
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation "androidx.appcompat:appcompat:$rootProject.ext.supportLibVersion"
}

Practical Application Example:

Suppose you are managing a project that includes a user interface (app module) and data processing (data module). You can define all modules' shared SDK versions and dependency library versions in the project-level build.gradle. This way, whenever you need to upgrade the SDK or library, you only need to update the version number in one place, and all modules will automatically use the new version, significantly simplifying maintenance work.

Advantages Summary:

• Consistency Guarantee: Ensures consistency across all modules in terms of compile SDK version, target SDK version, etc.
• Simplified Maintenance: When updating versions or dependencies, only one place needs to be modified.
• Reduced Errors: Minimizes build or runtime errors caused by inconsistent configurations.

By adopting this approach, using Gradle to manage multi-module build configurations for Android projects not only enhances efficiency but also ensures the maintainability and extensibility of the build system.