COMPILATION AND PROJECT BUILDING IN ANDROID (THE WHOLE PROCESS INVOLVED IN GETTING .APK FILE IN ANDROID )

COMPILATION AND PROJECT BUILDING PROCESS IN ANDROID 

The build process can be summarized as below:

• Resource code generation - The aapt (Android Asset Packaging Tool) tool takes your application resource files, such as the AndroidManifest.xml file and the XML files for your Activities, and compiles them. An R.java is also produced so you can reference your resources from your Java code.
• Interface code generation - The aidl (Android Interface Definition Language) tool converts any .aidl interfaces that you have into Java interfaces.
• Java compilation - The javac (Java Compiler) tool compiles all of your Java code, including the R.java and .aidl files, into .class files.
• Byte code conversion - The dex tool converts the .class files to Dalvik byte code. Any 3rd party libraries and .class files that you have included in your project are also converted into .dex files so that they can be packaged into the final .apk file.
• Packaging - The apkbuilder tool packages all non-compiled resources (such as images), compiled resources, and the .dex files into an .apk file.
• Signing the package - The jarsigner tool signs the .apk file with a debug key or a release key it can be installed to a device.
• Package optimization - The zipalign tool aligns the files in the .apk package to decreases memory usage when the application is running on a device.