Reusable Code

Reusable code is the holy grail of consulting, but there are many challenges to make reusable code work. In this talk we go through tips for building libraries, open or closed source, and making them successful and profitable.

Transcript

1. Reusable Libraries Ryan Harter @rharter +RyanHarter
2. My Apps Fragment Shift
3. Harter’s Tips for (Code) Happiness • Identify good candidates • Limit scope and requirements • Design a good API • Document and Communicate • Treat it like a client project
4. Identify Good Candidates
5. Identify Good Candidates • It’s not a library if it’s only used once • Don’t reinvent the wheel • Focus on core of app
6. Identify Good Candidates • Google for libraries • Check Android Arsenal • Look at what other apps use • Be Confident • Count Stars • Inspect Source
7. Fragment
8. Fragment
9. Fragment
10. Fragment
11. Fragment
12. Fragment
13. Fragment
14. Fragment
15. Fragment
16. Fragment
17. Fragment
18. Fragment
19. Fragment
20. Fragment
21. Fragment
22. Fragment
23. Fragment
24. Fragment
25. Fragment
26. Fragment
27. Fragment
28. Fragment
29. Fragment
30. Fragment
31. Fragment
32. Fragment
33. Fragment
34. Limit Scope and Requirements
35. 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
36. Limit Scope and Requirements • Library mission statement • One sentence • What the library does “Allow the user to load an image from any source.”
37. “Allow the user to load an image from any source.” Limit Scope and Requirements • Library mission statement • One sentence • What the library does
38. “Allow the user to load an image from any source.” Limit Scope and Requirements • Library mission statement • One sentence • What the library does
39. “Allow the user to load an image from any source.” Limit Scope and Requirements • Library mission statement • One sentence • What the library does
40. Design a Good API
41. 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
42. API Strategies - Utility Requirements: Persist filter state to support undo/redo.
43. API Strategies - Utility Requirements: Persist filter state to support undo/redo. public interface HistoryManager<T> { public T undo(); public T redo(); public void push(T state); public void clear(); }
44. 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() { … } } public class HistoryManager<T> { public T undo() { … } public T redo() { … } public void push(T state) { … } public void clear() { … } }
45. public class HistoryManager<T> { public HistoryManager(File file) { … } public T undo() { … } public T redo() { … } public void push(T state) { … } public void clear() { … } } API Strategies - Utility Requirements: Persist filter state to support undo/redo. public class HistoryManager<T> { public HistoryManager(File file) { … } public T undo() { … } public T redo() { … } public void push(T state) { … } public void clear() { … } }
46. public class HistoryManager<T> { public HistoryManager(File file) { … } public T undo() { … } public boolean canUndo() { … } public T redo() { … } public boolean canRedo() { … } public void push(T state) { … } public void clear() { … } } API Strategies - Utility Requirements: Persist filter state to support undo/redo. public class HistoryManager<T> { public HistoryManager(File file) { … } public T undo() { … } public boolean canUndo() { … } public T redo() { … } public boolean canRedo() { … } public void push(T state) { … } public void clear() { … } }
47. API Strategies - Superclass Fragment Shift
48. 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) { } }
49. 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) { } } 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) { } }
50. 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) { } } 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) { } }
51. 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) { } }
52. API Strategies - Isolated Activity Fragment Shift
53. API Strategies - Isolated Activity Intent i = new Intent(context, InspirationActivity.class); i.putExtra(EXTRA_USER_ID, "1234567890"); i.putExtra(EXTRA_ACCESS_TOKEN, "super_secret_access_token"); i.putExtra(EXTRA_SKIP_TAG, "fragmentpromo"); i.putExtra(EXTRA_USERNAME, "fragmentapp"); startActivity(i);
54. API Strategies - Isolated Activity <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" style="?attr/inspirationActivityStyle"> <ListView android:id="@android:id/list" style="?attr/inspirationListStyle"/> <TextView android:id="@+id/error" style="?attr/inspirationTextStyle"/> </FrameLayout>
55. API Strategies - Isolated Activity <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" style="?attr/inspirationActivityStyle"> <ListView android:id="@android:id/list" style="?attr/inspirationListStyle"/> <TextView android:id="@+id/error" style="?attr/inspirationTextStyle"/> </FrameLayout> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" style="?attr/inspirationActivityStyle"> <ListView android:id="@android:id/list" style="?attr/inspirationListStyle"/> <TextView android:id="@+id/error" style="?attr/inspirationTextStyle"/> </FrameLayout>
56. API Strategies - Isolated Activity <style name="AppTheme" parent=“Theme.AppCompat.NoActionBar"> <item name="inspirationActivityStyle">@style/FragmentInspirationStyle</item> <item name=“inspirationListStyle">@style/FragmentInspListStyle</item> <item name=“inspirationTextStyle">@style/FragmentInspTextStyle</item> </style>
57. API Strategies - Isolated Activity <style name="AppTheme" parent=“Theme.AppCompat.NoActionBar"> <item name="inspirationActivityStyle">@style/ShiftInspirationStyle</item> <item name=“inspirationListStyle">@style/ShiftInspListStyle</item> <item name=“inspirationTextStyle">@style/ShiftInspTextStyle</item> </style>
58. API Strategies - Hybrid
59. API Strategies - Hybrid Intent i = new Intent(this, ImageChooserActivity.class); startActivityForResult(i, REQUEST_CHOOSE_PHOTO);
60. Design a Good API UI Library Utility Library public interface ImageLoader {/ }/
61. Distribution • Open Source (jcenter, Maven Central) • Private Maven Repo
62. Document and Communicate
63. 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
64. Manage the Project
65. Manage the Project • Treat internal libraries like a client project • Dedicate resources • Manage requests • Define requirements • Enforce versioned release cycle
66. Reusable Libraries Ryan Harter @rharter +RyanHarter
67. Good Open Source Libraries
68. Android Arsenal https://android-arsenal.com
69. Retrofit public interface GithubService { List<Repo> listRepos(String user); } http://square.github.io/retrofit/ A type-safe REST client for Android and Java
70. Retrofit public interface GithubService { @GET("/users/{user}/repos") List<Repo> listRepos(@Path("user") String user); } http://square.github.io/retrofit/ A type-safe REST client for Android and Java
71. Retrofit public interface GithubService { @GET("/users/{user}/repos") List<Repo> listRepos(@Path("user") String user); } RestAdapter restAdapter = new RestAdapter.Builder() .setEndpoint("https://api.github.com") .build(); http://square.github.io/retrofit/ A type-safe REST client for Android and Java
72. Retrofit public interface GithubService { @GET("/users/{user}/repos") List<Repo> listRepos(@Path("user") String user); } RestAdapter restAdapter = new RestAdapter.Builder() .setEndpoint("https://api.github.com") .build(); GithubService service = restAdapter.create(GithubService.class); http://square.github.io/retrofit/ A type-safe REST client for Android and Java
73. Retrofit public interface GithubService { @GET("/users/{user}/repos") List<Repo> listRepos(@Path("user") String user); } RestAdapter restAdapter = new RestAdapter.Builder() .setEndpoint("https://api.github.com") .build(); GithubService service = restAdapter.create(GithubService.class); List<Repo> repos = service.listRepos("octocat"); http://square.github.io/retrofit/ A type-safe REST client for Android and Java
74. Retrofit public interface GithubService { @GET("/users/{user}/repos") List<Repo> listRepos(@Path("user") String user); } RestAdapter restAdapter = new RestAdapter.Builder() .setEndpoint("https://api.github.com") .build(); GithubService service = restAdapter.create(GithubService.class); List<Repo> repos = service.listRepos("octocat"); http://square.github.io/retrofit/ A type-safe REST client for Android and Java
75. Picasso http://square.github.io/picasso/ Picasso.with(context) .load(“http://i.imgur.com/DvpvklR.png") .into(imageView); A powerful image downloading and caching library for Android
76. Android Support https://developer.android.com/tools/support-library/features.html • AppCompat • ActionBar and friends • Material Themes • CardView • GridLayout • MediaRouter • Palette • RecyclerView
77. Calligraphy https://github.com/chrisjenx/Calligraphy Custom fonts in Android an OK way. <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" app:fontPath=“fonts/Roboto-Bold.ttf”/> <style name="AppTheme.Widget.TextView" parent="..."> <item name="fontPath">fonts/Roboto-ThinItalic.ttf</item> </style> Styles Direct
78. Butterknife http://jakewharton.github.io/butterknife/ View "injection" library for Android class ExampleActivity extends Activity { @InjectView(R.id.title) TextView title; @InjectView(R.id.subtitle) TextView subtitle; @InjectView(R.id.footer) TextView footer; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.simple_activity); ButterKnife.inject(this); // TODO Use "injected" views... } }
79. Butterknife http://jakewharton.github.io/butterknife/ View "injection" library for Android class ExampleActivity extends Activity { @InjectView(R.id.title) TextView title; @InjectView(R.id.subtitle) TextView subtitle; @InjectView(R.id.footer) TextView footer; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.simple_activity); ButterKnife.inject(this); // TODO Use "injected" views... } }
80. Reusable Libraries Ryan Harter @rharter +RyanHarter