How to Build an Android Jar Library

To build an Android Jar library, you can follow these steps:

1. Create a build.xml file with the following content:

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<project name="AndroidUtils" default="dist" basedir=".">
    <description>Android Sample Library</description>
    
    <!-- Setting global properties for this build -->
    <property name="src" location="src" />
    <property name="bin" location="bin" />

    <target name="dist">
        <jar destfile="android-utilities-v1.jar" basedir="bin/classes">
            <!-- Use ** to include the directory recursively -->
            <include name="android/**" />
            <exclude name="android/utilities/v1/R.class" />
            <exclude name="android/utilities/v1/R$*.class" />
        </jar>
    </target>
</project>

2. Save the build.xml file in the root directory of your Android library project.

3. Install Apache Ant on your system if you haven’t already. Ant is a build tool that can compile and package your Java code into a Jar file. You can download Ant from the Apache Ant website.

4. Open a command prompt or terminal and navigate to the root directory of your Android library project.

5. Run the following command to build the Jar file using Ant:

ant dist

6. After the build process completes successfully, you will find the generated Jar file named android-utilities-v1.jar in the bin directory of your project.

Obfuscating an Android Jar

If you want to obfuscate your Android Jar to protect your code and reduce its size, you can use ProGuard, which is a popular Java optimization and obfuscation tool. Follow these steps to obfuscate your Android Jar:

1. Download ProGuard from the official ProGuard website.

2. Extract the downloaded ProGuard package to a directory on your system.

3. Open the ProGuard GUI by executing the appropriate command based on your operating system:

   • Windows: Run proguardgui.bat.
   • Linux/macOS: Run ./proguardgui.sh.

4. In the ProGuard GUI, go to the “Input/Output” tab.

5. Add your input Jar file (e.g., android-utilities-v1.jar) to the “Input” section.

6. Specify the output Jar file (e.g., android-utilities-v1-obfuscated.jar) in the “Output” section.

7. In the “Library” section, add android.jar as an input/output file. This is necessary to provide the necessary Android framework classes for the obfuscation process.

8. Switch to the “Shrinking” tab.

9. In the “Keep” section, uncheck “Application” and check “Library”. This configuration ensures that only the necessary code is retained and the rest can be obfuscated.

10. Click on the “Process” button to start the obfuscation process.

11. After the process completes, you will find the obfuscated Jar file (e.g., android-utilities-v1-obfuscated.jar) in the specified output location.

That’s it! You have successfully built an Android Jar library and obfuscated it using ProGuard.