Android Libraries and APIs 

Software Library  Collection of “implementations”, with easy to call hooks.  Helps remove redundancy of similar functionality from apps  Helps abstracting higher level development away from lower level development  Static library -> Built and distributed with the app  Dynamic library -> linked from the software 

Application programming interface  How software components should interact  Can be in form of a library or just documentation  ABI = Application Binary Interface; for closed source binary function call hooks  Some APIs are internationally standardised  In procedural languages -> like header files  In OOP languages -> like importable classes 

Software Development Kit  Set of tools to create a software for a particular platform.  Usually a set of APIs, building tools and configs, debugging & testing utilities  SDK's license can dictate the freeness of the software you develop  A non-distributable copy of platform could be part of sdk 

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Libraries in Android  .jar -> are just Java libraries  .jar libraries are mostly functionality based libraries, where data handling, data manipulation, service/framework integration is handled  Generally cannot be used to implement UX/UI features as android resources not present 

Libraries in Android  .aar -> android library  Contain java code along with android resources and also android manifest stubs  Project structure exactly as an Android app  **Support only recently added in Android Studio 0.5.0 

Libraries in Android  Open source libraries -> distributed as form of the whole directory structure from where project was built  Need to import the whole project into IDE and add it as a module on which your App depends 

Creating your own Android Library  Step 1 : Decide whether to use only-java library or a full android library  Step 2 : Create data-agnostic functions/classes in library. Keep in mind various different apps will use the library  Step 3 : Make sure functions to be used by client program are public and everything else private 

Creating your own Android Library  Step 4 : Properly document the usage of the library. If not for anyone else but for yourself  Step 5 : Test properly for all use cases and corner cases  Step 6 : Decide distribution methodology (open source, binary etc)  Step 7 : Distribute, share documentation, popularise, rejoice !! 

Need for documentation  A library is written for third party usage  The person who will develop a software using your library needs to know how to make best use of your library  Even open source libraries must have proper documentation because you should not expect 3rd party to understand your code. 

Javadoc : Documenting Java code  Generally documentation invloves writing comments in code. Javadoc takes the step further.  Write comments in code in javadoc format, then run javadoc on the source, and get autogenerated software-manual like HTML pages 

Javadoc : Documenting Java code  Basic structure : enclose in /** */ 

Javadoc : Documenting Java code