Keep calm and write reusable code in Android
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The document discusses the importance of code reusability in Android development, tracing its history and explaining various techniques and types of reuse. It highlights common challenges, such as the pitfalls of overly generic code and the prevalent use of copy-and-paste programming. Additionally, it outlines effective practices for building reusable components within Android applications, focusing on modular architecture and the benefits of using libraries.
Keep calm and write reusable code in Android
- 1. Keep calm and write reusable code in Android Juan Camilo Sacanamboy Co-founder and mobile developer at Peewah http://peewah.co
- 2. Content 1. Code reusability 2. The most used technique 3. Code reusability in Android
- 4. History ● 1968: Douglas Mcllroy of Bell Laboratories proposed basing the software industry on reusable components ● Write once and use it in many projects ● Not only reuse the code but also test suites, designs, documentation, and so on. ● Improve the code duplication caused by copy & paste programming
- 5. Types of reuse Concerning motivation and driving factors, reuse can be: ● Opportunistic ● Planned Reuse can be categorized further: ● Internal reuse ● External reuse Concerning form or structure of reuse, code can be: ● Referenced ● Forked
- 6. Examples ● Software libraries ● Design patterns ● Higher-order function ● Retrocomputing ● Components ● Outside of computers
- 7. Reusable software? Just don’t write generic code ● “It’s a common mistake to make software too generic” ● “Maximizing genericity complicates use” ● “Reusable software requires loose coupling and strong cohesion” ● Pitfalls ○ Abstraction layers everywhere ○ Excessive use of inheritance Reference: http://josdejong.com/blog/2015/01/06/code-reuse/
- 8. 2. The most used technique
- 9. Yes! It’s the copy & paste programming
- 10. The Last Line Effect ● 84 code fragments ○ 41 contain mistakes somewhere in the middle ○ 43 contain mistakes in the last copied code block Reference: http://www.viva64.com/en/b/0260/ - Andrey Karpov Figure 1. A rough diagram of mistake distribution in five homogeneous code blocks. The probability of making a mistake in the last pasted block of code is 4 times higher than in any other block.
- 11. Examples Reference: http://www.viva64.com/en/b/0260/ - Andrey Karpov Source Engine SDK Chromium
- 12. Examples Reference: http://www.viva64.com/en/b/0260/ - Andrey Karpov ReactOS Multi Theft Auto
- 13. Examples Reference: http://www.viva64.com/en/b/0260/ - Andrey Karpov Source Engine SDK
- 14. Code reusability in Android
- 15. Activities “An application component that provides a screen with which users can interact in order to do something…each activity is given a window in which to draw its user interface.” Reference: http://developer.android.com/guide/components/activities.html
- 16. Fragments Added in API level 11 (Android 3.0) “A modular section of an activity, which has its own lifecycle, receives its own input events, and which you can add or remove while the activity is running” Reference: http://developer.android.com/guide/components/activities.html
- 17. Java Archive (jar) vs Android Archive (aar) ● jar: Java classes ● aar: drawables, layouts, assets, styles, Android Manifest, libs, and so on In Android Studio (Gradle build) you can use library in 3 ways 1. Library is a separate module in a project (multi-module project) 2. Library can be stored locally in the project (typically in libs folder) 3. Library can be deployed into a repository (Maven, Ivy Repository, JCenter) Reference: http://stackoverflow.com/questions/29450709/how-to-create-reusable-activities-in-android
- 18. Multi-module project ● Multiple APKs with common library with a multi-module project (some modules are libraries, some modules are applications. ● Problem: many apps in the same project. dependencies { project(":library-module") } Reference: http://stackoverflow.com/questions/29450709/how-to-create-reusable-activities-in-android
- 19. Locally stored library ● Compile classes in a jar file ● Problem: updating local jar every time you update the library Reference: http://stackoverflow.com/questions/29450709/how-to-create-reusable-activities-in-android dependencies { compile files('libs/some_library.jar') }
- 20. Deployed libraries ● The best way to use libraries in a project ● You need a server (unless you create an open source, in that case you can use Maven Center or jCenter) ● You can use a local repository, but that’s difficult when you’re working with other developers dependencies { compile 'com.google.code.gson:gson:2.2.4' } Reference: http://stackoverflow.com/questions/29450709/how-to-create-reusable-activities-in-android
- 22. Peewah’s product: Native apps for events ● Home ● Schedule (by day and topic) ● Twitter feed ● Gallery ● Photobooth ● Maps ● Phone numbers
- 23. Peewah’s architecture (native apps for events)
- 24. Characteristics of our architecture ● The library is an Android Module ● Each menu is a fragment and it’s decoupled from the others ● Each menu has parameters to configure it ● If there are dependencies between fragments we use a publisher/subscriber mechanism (Otto) ● The library don’t depend of the technology used in the backend
- 25. The library is an Android Module
- 26. Each menu is a fragment and it’s decoupled
- 27. Each menu has parameters to configure it
- 28. Publisher/subscriber mechanism for dependencies MainActivity notifies two type of events to the subscribers: Events and Milestones The fragment (subscriber) receives the information The fragment subscribes to the Activity (publisher)
- 29. Don’t depend of the technology used in the backend
- 30. Before our library ● Average development time: 2 months ● Many classes, activities, fragments, layouts (>60)
- 31. After our library ● Average development time: 1 week ● One class in the app (MainActivity) Add menus in the Main Activiy
- 32. After our library Add Home Menu to the Main Activity with the Library (3 lines of code)