Integrate a library inside a library as .aar in .aar

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07-10-2024

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Integrating a Library Inside a Library: The .aar within an .aar

In the world of Android development, libraries play a crucial role in simplifying development and streamlining projects. But what happens when you need to incorporate a library within another library? This is where the concept of .aar within an .aar comes into play.

The Problem: Need for Library Bundling

Let's imagine you're building a custom UI library, MyAwesomeUI, that relies on a popular animation library, FancyAnimations. You want to distribute MyAwesomeUI as a single, easy-to-use .aar file. However, you also need to include the FancyAnimations library within the MyAwesomeUI .aar to avoid users having to include it separately.

Original Code (Simplified Example):

MyAwesomeUI Project:

dependencies {
    implementation("com.example:fancy-animations:1.0.0")
}

Output: MyAwesomeUI.aar (without FancyAnimations)

Solution: .aar within an .aar

This is where the .aar within an .aar approach shines. We can bundle the FancyAnimations library within MyAwesomeUI during the build process.

Revised Project Setup:

1. Create a libs directory: Inside your MyAwesomeUI project, create a libs directory.
2. Add the FancyAnimations.aar: Download the FancyAnimations.aar and place it within the libs directory.
3. Modify your build.gradle:

android {
    ...
    buildTypes {
        release {
            minifyEnabled false // Disable minification for now
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
            // Add the following lines to bundle FancyAnimations
            aaptOptions {
                noCompress "libs/"
            }
            packagingOptions {
                doNotStrip "**/*.so" // Prevents native libraries from being stripped
            }
        }
    }
}

dependencies {
    //  No longer directly needed
    // implementation("com.example:fancy-animations:1.0.0") 
}

Explanation and Key Points:

• noCompress: This option ensures that the FancyAnimations.aar is included in the final MyAwesomeUI.aar without being compressed by the aapt tool.
• doNotStrip: This prevents native libraries within FancyAnimations from being stripped during the build process.
• Dependency Removal: You can now remove the direct dependency on FancyAnimations in the build.gradle as it's being bundled.
• Minification (Optional): For production builds, you might need to adjust proguard rules to ensure that FancyAnimations classes and resources are not stripped during minification.

Benefits:

• Simplified Integration: Users of MyAwesomeUI don't have to deal with separate dependencies for FancyAnimations.
• Reduced Project Complexity: A single .aar for MyAwesomeUI is easier to manage and distribute.
• Improved Maintainability: Changes to FancyAnimations are handled within the MyAwesomeUI project.

Things to Keep in Mind:

• Version Conflicts: Be mindful of potential version conflicts between libraries. Ensure that the FancyAnimations version bundled within MyAwesomeUI is compatible with the rest of your project.
• Testing: Thoroughly test your MyAwesomeUI library after bundling to ensure that all dependencies are working correctly.
• Alternative Approach: If you have many dependencies or complex dependencies, consider using a dependency management system like Maven or Gradle to manage the integration process.

Conclusion:

The .aar within an .aar approach is a valuable technique for building modular libraries and simplifying project dependencies. While it requires some modifications to your build process, it can significantly improve the usability and maintainability of your library projects.