[Droidcon Berlin '17] Things I wish I knew when I started building Android sdk/libraries

As more and more people start building Android Libraries, the whole process of building a better API for developers is getting bloated and everyone is coming up with their own ideas. However, if android library developers follow a certain standard with a rationale they can avoid most of the pitfalls. Building an android library is easy, but building one that keeps in mind developer happiness is rare but definitely not hard. The session would cover how one can build android libraries taking in consideration to exposing more informative API, making sure the best resources are utilized efficiently and that one does not force the app developer with redundant dependencies and complexities.

Animated Gif Version: https://goo.gl/WNeR4A

Video: https://www.youtube.com/watch?v=RAZEIrmtUPo

Link to blog post: https://android.jlelse.eu/things-i-wish-i-knew-when-i-started-building-android-sdk-libraries-dba1a524d619

Sketchnotes by:
Chiu-Ki Chan: https://twitter.com/chiuki/status/905046880723329024
Garima Jain: https://twitter.com/ragdroid/status/905053186318368770
Miriam Busch: https://twitter.com/miphoni/status/905174390312239105

Transcript

1. Things I wish I knew when I started building android SDK/libraries Nishant Srivastava
2. Nishant Srivastava @nisrulz
3. @nisrulz #droidconDE Sensey https://github.com/nisrulz/sensey EasyDeviceInfo https://github.com/nisrulz/easydeviceinfo
4. Wait... what is an Android Library? @nisrulz #droidconDE
5. Android Library is... @nisrulz #droidconDE
6. Android Library is... <secret ingredient> + <secret ingredient> + <secret ingredient> = <Android Library> @nisrulz #droidconDE
7. Android Library is... Java code + <secret ingredient> + <secret ingredient> = <Android Library> @nisrulz #droidconDE
8. Android Library is... Java code + Android resources + <secret ingredient> = <Android Library> @nisrulz #droidconDE
9. Android Library is... Java code + Android resources + Android Manifest stub = <Android Library> @nisrulz #droidconDE
10. Android Library is... Java code + Android resources + Android Manifest stub = Android ARchive (AAR) @nisrulz #droidconDE
11. Why create an Android Library? @nisrulz #droidconDE
12. Why create an Android Library? Short Answer @nisrulz #droidconDE
13. Why create an Android Library? Short Answer You don’t have to… @nisrulz #droidconDE
14. Why create an Android Library? Short Answer You don’t have to… ...unless a solution already exists. Then use that. @nisrulz #droidconDE
15. Best Practices for building android libraries... ...that said, let us move on to @nisrulz #droidconDE
16. Ease of use @nisrulz #droidconDE
17. Ease of use Intuitive @nisrulz #droidconDE
18. Ease of use Intuitive Consistent @nisrulz #droidconDE
19. Ease of use Intuitive Consistent Easy to use, Hard to misuse @nisrulz #droidconDE
20. Avoid multiple arguments // Do not DO this void init(String apikey, int refresh, long interval, String type, String username, String email, String password); @nisrulz #droidconDE
21. Avoid multiple arguments // Do not DO this void init(String apikey, int refresh, long interval, String type, String username, String email, String password); // WHY? void init(“0123456789”,“prod”, 1000, 1, “nishant”, ”1234”, “nisrulz@gmail.com”); // Passing arguments in right order is easy to mess up here :( @nisrulz #droidconDE
22. Avoid multiple arguments // Do this void init(ApiSecret apisecret); @nisrulz #droidconDE
23. Avoid multiple arguments // Do this void init(ApiSecret apisecret); // where ApiSecret is public class ApiSecret{ String apikey; int refresh; long interval; String type; String name; String email; String pass; // constructor // validation checks(such as type safety) // setter and getters } @nisrulz #droidconDE
24. Avoid multiple arguments // Or use Builder Pattern AwesomeLib awesomelib = new AwesomeLib.AwesomeLibBuilder() .apisecret(mApisecret).refresh(mRefresh) .interval(mInterval).type(mType) .username(mUsername).email(mEmail).password(mPassword) .build(); } @nisrulz #droidconDE
25. Minimize Permissions @nisrulz #droidconDE
26. Minimize Permissions Use intents @nisrulz #droidconDE
27. Minimize Permissions Use intents Reduce req. permissions @nisrulz #droidconDE
28. Minimize Permissions Use intents Reduce req. permissions Check permission, use fallbacks @nisrulz #droidconDE
29. Minimize Permissions Use intents Reduce req. permissions Check permission, use fallbacks public boolean hasPermission(Context context, String permission) { int result = context.checkCallingOrSelfPermission(permission); return result == PackageManager.PERMISSION_GRANTED; } @nisrulz #droidconDE
30. Minimize Feature Requisite // Do not do this <uses-feature android:name="android.hardware.bluetooth" /> @nisrulz #droidconDE
31. Minimize Feature Requisite // Do not do this <uses-feature android:name="android.hardware.bluetooth" /> // Runtime feature detection String feature = PackageManager.FEATURE_BLUETOOTH; public boolean isFeatureAvailable(Context context, String feature) { return context.getPackageManager().hasSystemFeature(feature); } // Enable/Disable the functionality depending on availability of feature @nisrulz #droidconDE
32. Support different versions // RULE OF THUMB : Support the full spectrum of android versions @nisrulz #droidconDE
33. Support different versions // RULE OF THUMB : Support the full spectrum of android versions android { ... defaultConfig { .. minSdkVersion 9 targetSdkVersion 26 .. } } @nisrulz #droidconDE
34. Support different versions // How?? : Detect version and Enable/Disable features or use // a fallback @nisrulz #droidconDE
35. Support different versions // How?? : Detect version and Enable/Disable features or use // a fallback public boolean isOreoAndAbove(){ return Build.VERSION.SDK_INT>= Build.VERSION_CODES.O; } @nisrulz #droidconDE
36. Don’t log in production @nisrulz #droidconDE
37. Don’t log in production ...but log exceptions/errors @nisrulz #droidconDE
38. Don’t log in production ...but log exceptions/errors Provide flagged logging support AwesomeLibrary.init(apisecret,BuildConfig.DEBUG); @nisrulz #droidconDE
39. Don’t log in production // Provide flexibility to log when debug flag is true void init(ApiSecret apisecret,boolean debuggable){ try{ ... } catch(Exception ex){ if (debuggable){ // This is printed only when debuggable is true ex.printStackTrace(); } } } @nisrulz #droidconDE
40. Don’t log in production // Provide flexibility to log when debug flag is true void init(ApiSecret apisecret,boolean debuggable){ try{ ... } catch(Exception ex){ if (debuggable){ // This is printed only when debuggable is true ex.printStackTrace(); } } } @nisrulz #droidconDE
41. Degrade gracefully on error @nisrulz #droidconDE
42. Degrade gracefully on error Do not crash the app @nisrulz #droidconDE
43. Degrade gracefully on error Do not crash the app Disable feature/functionality @nisrulz #droidconDE
44. Catch specific exception // Do not do this try { // ... } catch(Exception e) { // ... } @nisrulz #droidconDE
45. Catch specific exception // Do this try { // ... } catch(IOException e) { // ... } @nisrulz #droidconDE
46. Handle poor network conditions @nisrulz #droidconDE
47. Handle poor network conditions Acknowledge unreliable network exists @nisrulz #droidconDE
48. Handle poor network conditions Acknowledge unreliable network exists Batch network calls @nisrulz #droidconDE
49. Handle poor network conditions Acknowledge unreliable network exists Batch network calls Prefetch data ahead of time @nisrulz #droidconDE
50. Handle poor network conditions Acknowledge unreliable network exists Batch network calls Prefetch data ahead of time Use better data structures such as flatbuffers @nisrulz #droidconDE
51. Implementation/api VS compile Before Gradle 4.0 compile Gradle 4.0+ onwards implementation api @nisrulz #droidconDE
52. Require min dependencies Keep a check on method count http://www.methodscount.com/plugins @nisrulz #droidconDE
53. Require min dependencies Let the app developer make the decision about inclusion @nisrulz #droidconDE
54. Require min dependencies Let the app developer make the decision about inclusion AwesomeLib module: dependencies { // Gradle v2.12 and below provided 'com.squareup.retrofit2:retrofit:2.1.0' // Gradle v2.12+ compileOnly 'com.squareup.retrofit2:retrofit:2.1.0' } @nisrulz #droidconDE
55. Require min dependencies Let the app developer make the decision about inclusion AwesomeLib module: dependencies { // Gradle v2.12 and below provided 'com.squareup.retrofit2:retrofit:2.1.0' // Gradle v2.12+ compileOnly 'com.squareup.retrofit2:retrofit:2.1.0' } @nisrulz #droidconDE
56. Require min dependencies Let the app developer make the decision about inclusion App module: dependencies { // ... implementation 'com.squareup.retrofit2:retrofit:2.1.0' } @nisrulz #droidconDE
57. Require min dependencies Enable/Disable feature based on availability private boolean hasRetrofitOnClasspath() { try { Class.forName("retrofit2.Retrofit"); return true; } catch (ClassNotFoundException ex) { ex.printStackTrace(); } return false; } @nisrulz #droidconDE
58. Require min dependencies Enable/Disable feature based on availability private boolean hasRetrofitOnClasspath() { try { Class.forName("retrofit2.Retrofit"); return true; } catch (ClassNotFoundException ex) { ex.printStackTrace(); } return false; } @nisrulz #droidconDE
59. Lifecycle Arch Components @nisrulz #droidconDE
60. Lifecycle Arch Components public class AwesomeLib implements LifecycleObserver{ @OnLifecycleEvent(Lifecycle.Event.ON_CREATE) public void executeFnOnCreate(){ // do something on create } @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) public void cleanup(){ // do some cleanup tasks } } @nisrulz #droidconDE
61. Lifecycle Arch Components public class AwesomeLib implements LifecycleObserver{ @OnLifecycleEvent(Lifecycle.Event.ON_CREATE) public void executeFnOnCreate(){ // do something on create } @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) public void cleanup(){ // do some cleanup tasks } } @nisrulz #droidconDE
62. Lifecycle Arch Components public class MainActivity extends LifecycleActivity { AwesomeLib awesomeLib; @Override protected void onCreate(Bundle savedInstanceState) { // .. awesomeLib = new AwesomeLib(); getLifecycle().addObserver(awesomeLib); } @Override protected void onDestroy() { // ... getLifecycle().removeObserver(awesomeLib); } } @nisrulz #droidconDE
63. Lifecycle Arch Components public class MainActivity extends LifecycleActivity { AwesomeLib awesomeLib; @Override protected void onCreate(Bundle savedInstanceState) { // .. awesomeLib = new AwesomeLib(); getLifecycle().addObserver(awesomeLib); } @Override protected void onDestroy() { // ... getLifecycle().removeObserver(awesomeLib); } } @nisrulz #droidconDE
64. Do not hog the startup @nisrulz #droidconDE
65. Do not hog the startup @nisrulz #droidconDE
66. Do not hog the startup You do not need to initialize everything, @nisrulz #droidconDE
67. Do not hog the startup You do not need to initialize everything, Try to do lazy initialization @nisrulz #droidconDE
68. Remove functionality gracefully /** * @deprecated As of release 2.0, replaced by {@link #getPreferredSize()} */ @Deprecated public Dimension preferredSize() { return getPreferredSize(); } @nisrulz #droidconDE
69. Document everything Provide Readme.md @nisrulz #droidconDE
70. Document everything Provide Readme.md Include javadocs in code @nisrulz #droidconDE
71. Document everything Provide Readme.md Include javadocs in code Bundle a sample app @nisrulz #droidconDE
72. Document everything Provide Readme.md Include javadocs in code Bundle a sample app Maintain a changelog http://keepachangelog.com @nisrulz #droidconDE
73. Document everything @nisrulz #droidconDE
74. License is Important https://choosealicense.com/ @nisrulz #droidconDE
75. License is Important /* * Copyright (C) 2016 Nishant Srivastava * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ @nisrulz #droidconDE
76. Versioning Strategy Define a versioning scheme i.e MAJOR.MINOR.PATCH http://semver.org/ @nisrulz #droidconDE
77. Versioning Strategy To make 2 versions coexist, release under a new group ID @nisrulz #droidconDE
78. Versioning Strategy To make 2 versions coexist, release under a new group ID i.e 1.x = io.reactivex:rxjava:x.y.z 2.x = io.reactivex.rxjava2:rxjava:2.x.y @nisrulz #droidconDE
79. Proguard, wait… what? @nisrulz #droidconDE
80. Proguard, wait… what? Proguard rules can be shipped in an android library @nisrulz #droidconDE
81. Proguard, wait… what? Proguard rules can be shipped in an android library android { ... defaultConfig { ... versionName "1.0.0" ... consumerProguardFiles 'consumer-proguard-rules.pro' } } @nisrulz #droidconDE
82. Proguard, wait… what? @nisrulz #droidconDE
83. Proguard, wait… what? @nisrulz #droidconDE
84. Proguard, wait… what? @nisrulz #droidconDE
85. References BlogPost:https://android.jlelse.eu/things-i-wish-i-knew-when-i-star ted-building-android-sdk-libraries-dba1a524d619 My open sourced android libraries:https://github.com/nisrulz/nisrulz.github.io#open-source- contributions Sensey:https://github.com/nisrulz/sensey EasyDeviceInfo:https://github.com/nisrulz/easydeviceinfo
86. Credits Emoji Icons designed by Freepik from Flaticon
87. Thank You Q & A twitter.com/ nisrulz github.com/ nisrulz .com
88. Things I wish I knew when I started building android SDK/libraries twitter.com/ nisrulz github.com/ nisrulz .com