Reusable Libraries

How to make reusable code work on Android.

Transcript

1. Reusable Libraries Ryan Harter @rharter +RyanHarter
2. My Apps Fragment Shift
3. My Apps Fragment Shift
4. My Apps Fragment Shift
5. Steps to make libraries work • Identify good candidates • Limit scope and requirements • Design a good API • Document and Communicate • Treat it like a client project
6. Identify Good Candidates
7. Identify Good Candidates
8. Identify Good Candidates • It’s not a library if it’s only used once
9. Identify Good Candidates • It’s not a library if it’s only used once • Don’t reinvent the wheel
10. Identify Good Candidates • It’s not a library if it’s only used once • Don’t reinvent the wheel • Two Categories
11. Identify Good Candidates • It’s not a library if it’s only used once • Don’t reinvent the wheel • Two Categories • Utility
12. Identify Good Candidates • It’s not a library if it’s only used once • Don’t reinvent the wheel • Two Categories • Utility • UI
13. Identify Good Candidates
14. Identify Good Candidates • Google for libraries
15. Identify Good Candidates • Google for libraries • Check Android Arsenal
16. Identify Good Candidates • Google for libraries • Check Android Arsenal • Look at what other apps use
17. Identify Good Candidates • Google for libraries • Check Android Arsenal • Look at what other apps use • Be Confident
18. Identify Good Candidates • Google for libraries • Check Android Arsenal • Look at what other apps use • Be Confident • Count Stars
19. Identify Good Candidates • Google for libraries • Check Android Arsenal • Look at what other apps use • Be Confident • Count Stars • Inspect Source
20. Limit Scope and Requirements
21. Limit Scope and Requirements
22. Limit Scope and Requirements • Choose a single problem to solve
23. Limit Scope and Requirements • Choose a single problem to solve • Picasso - Efficient image loading and caching
24. Limit Scope and Requirements • Choose a single problem to solve • Picasso - Efficient image loading and caching • Retrofit - Easy REST API access
25. Limit Scope and Requirements • Choose a single problem to solve • Picasso - Efficient image loading and caching • Retrofit - Easy REST API access • Avoid “Apache Syndrome”
26. Limit Scope and Requirements • Choose a single problem to solve • Picasso - Efficient image loading and caching • Retrofit - Easy REST API access • Avoid “Apache Syndrome” • Every Apache library depends on every other Apache library
27. Limit Scope and Requirements • Library mission statement • One sentence • What the library does
28. Limit Scope and Requirements • Library mission statement • One sentence • What the library does “Allow the user to load an image from any source.”
29. Design a Good API
30. Design a Good API
31. Design a Good API • Who is your user?
32. Design a Good API • Who is your user? • If user needs to mess with code, it’s not a library
33. Design a Good API • Who is your user? • If user needs to mess with code, it’s not a library • Design from the outside in
34. Design a Good API • Who is your user? • If user needs to mess with code, it’s not a library • Design from the outside in • Package your library
35. API Strategies - Utility Requirements: Persist filter state to support undo/redo. public class HistoryManager<T> { public T undo(); public T redo(); public void push(T state); public void clear(); }
36. API Strategies - Superclass Fragment Shift
37. API Strategies - Superclass public class BaseExportActivity extends Activity { /** * Returns a list of preferred packages which appear above the * divider with a slightly larger icon than the rest. * * @return the package ids of the preferred packages. */ protected List<String> getPreferredPackages() { return DEFAULT_PREFERRED_PACKAGES; } /** * @return the public folder name to save files to. */ protected File getSaveFolder() { return new File(getPublicPicturesDirectory(), "Pixite"); } /** * Allows the AppInfo to be updated for things like Refragment or * Refilter. Default implementation does nothing. * * @param info The app info to update. */ protected void updateAppInfo(AppInfo info) { } }
38. API Strategies - Isolated Activity Fragment Shift
39. API Strategies - Isolated Activity
40. API Strategies - Isolated Activity Intent i = new Intent(getActivity(), InspirationActivity.class); i.putExtra(InspirationActivity.EXTRA_USER_ID, "1234567890"); i.putExtra(InspirationActivity.EXTRA_ACCESS_TOKEN, "super_secret_access_token"); i.putExtra(InspirationActivity.EXTRA_SKIP_TAG, "shiftpromo"); i.putExtra(InspirationActivity.EXTRA_USERNAME, "shift_by_pixite"); startActivity(i);
41. API Strategies - Isolated Activity Intent i = new Intent(getActivity(), InspirationActivity.class); i.putExtra(InspirationActivity.EXTRA_USER_ID, "1234567890"); i.putExtra(InspirationActivity.EXTRA_ACCESS_TOKEN, "super_secret_access_token"); i.putExtra(InspirationActivity.EXTRA_SKIP_TAG, "shiftpromo"); i.putExtra(InspirationActivity.EXTRA_USERNAME, "shift_by_pixite"); startActivity(i); <style name="AppTheme" parent="Theme.AppCompat.NoActionBar"> ... <item name="inspirationActivityStyle">@style/InspirationActivityStyle</item> <item name="inspirationTextStyle">@style/TextAppearance.AppCompat.Inverse</item> <item name="inspirationFollowButtonStyle">@style/Widget.InspirationButton.Follow</item> <item name="inspirationMoreButtonStyle">@style/Widget.InspirationButton.More</item> <item name="inspirationRowStyle">@style/Widget.InspirationRow</item> <item name="inspirationRowTextStyle">@style/TextAppearance.InspirationRow</item> </style>
42. API Strategies - Hybrid Intent i = new Intent(this, ImageChooserActivity.class); startActivityForResult(i, REQUEST_CHOOSE_PHOTO);
43. Distribution • Open Source (jcenter, Maven Central) • Private Maven Repo • Git Repository
44. Distribution - gradle-git-repo uploadArchives { repositories { mavenDeployer { repository(url: 'git@github.com:rharter/maven-repo.git/releases') snapshotRepository(url: ‘git@github.com:rharter/maven-repo.git/snapshots') // standard pom settings } } } https://github.com/rharter/gradle-git-repo
45. Document and Communicate
46. Document and Communicate
47. Document and Communicate • If a library is only used once, is it a library?
48. Document and Communicate • If a library is only used once, is it a library? • Communicate outside of engineering
49. Document and Communicate • If a library is only used once, is it a library? • Communicate outside of engineering • Sales needs to know what to sell
50. Document and Communicate • If a library is only used once, is it a library? • Communicate outside of engineering • Sales needs to know what to sell • Design needs to know components and limitations
51. Document and Communicate • If a library is only used once, is it a library? • Communicate outside of engineering • Sales needs to know what to sell • Design needs to know components and limitations • Javadoc for Engineering, Wiki for others
52. Manage the Project
53. Manage the Project
54. Manage the Project • Treat internal libraries like a client project
55. Manage the Project • Treat internal libraries like a client project • Dedicate resources
56. Manage the Project • Treat internal libraries like a client project • Dedicate resources • Manage requests
57. Manage the Project • Treat internal libraries like a client project • Dedicate resources • Manage requests • Define requirements
58. Manage the Project • Treat internal libraries like a client project • Dedicate resources • Manage requests • Define requirements • Enforce versioned release cycle
59. Reusable Libraries @rharter +RyanHarter http://ryanharter.com