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

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Things I wish I knew when I started building android SDK/libraries Nishant Srivastava

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Nishant Srivastava @nisrulz

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@nisrulz #droidconDE Sensey https://github.com/nisrulz/sensey EasyDeviceInfo https://github.com/nisrulz/easydeviceinfo

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Wait... what is an Android Library? @nisrulz #droidconDE

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Android Library is... @nisrulz #droidconDE

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Android Library is... + + = @nisrulz #droidconDE

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Android Library is... Java code + + = @nisrulz #droidconDE

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Android Library is... Java code + Android resources + = @nisrulz #droidconDE

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Android Library is... Java code + Android resources + Android Manifest stub = @nisrulz #droidconDE

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Android Library is... Java code + Android resources + Android Manifest stub = Android ARchive (AAR) @nisrulz #droidconDE

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Why create an Android Library? @nisrulz #droidconDE

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Why create an Android Library? Short Answer @nisrulz #droidconDE

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Why create an Android Library? Short Answer You don’t have to… @nisrulz #droidconDE

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Why create an Android Library? Short Answer You don’t have to… ...unless a solution already exists. Then use that. @nisrulz #droidconDE

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Best Practices for building android libraries... ...that said, let us move on to @nisrulz #droidconDE

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Ease of use @nisrulz #droidconDE

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Ease of use Intuitive @nisrulz #droidconDE

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Ease of use Intuitive Consistent @nisrulz #droidconDE

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Ease of use Intuitive Consistent Easy to use, Hard to misuse @nisrulz #droidconDE

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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

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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

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Avoid multiple arguments // Do this void init(ApiSecret apisecret); @nisrulz #droidconDE

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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

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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

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Minimize Permissions @nisrulz #droidconDE

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Minimize Permissions Use intents @nisrulz #droidconDE

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Minimize Permissions Use intents Reduce req. permissions @nisrulz #droidconDE

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Minimize Permissions Use intents Reduce req. permissions Check permission, use fallbacks @nisrulz #droidconDE

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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

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Minimize Feature Requisite // Do not do this @nisrulz #droidconDE

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Minimize Feature Requisite // Do not do this // 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

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Support different versions // RULE OF THUMB : Support the full spectrum of android versions @nisrulz #droidconDE

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Support different versions // RULE OF THUMB : Support the full spectrum of android versions android { ... defaultConfig { .. minSdkVersion 9 targetSdkVersion 26 .. } } @nisrulz #droidconDE

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Support different versions // How?? : Detect version and Enable/Disable features or use // a fallback @nisrulz #droidconDE

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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

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Don’t log in production @nisrulz #droidconDE

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Don’t log in production ...but log exceptions/errors @nisrulz #droidconDE

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Don’t log in production ...but log exceptions/errors Provide flagged logging support AwesomeLibrary.init(apisecret,BuildConfig.DEBUG); @nisrulz #droidconDE

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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

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Degrade gracefully on error @nisrulz #droidconDE

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Degrade gracefully on error Do not crash the app @nisrulz #droidconDE

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Degrade gracefully on error Do not crash the app Disable feature/functionality @nisrulz #droidconDE

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Catch specific exception // Do not do this try { // ... } catch(Exception e) { // ... } @nisrulz #droidconDE

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Catch specific exception // Do this try { // ... } catch(IOException e) { // ... } @nisrulz #droidconDE

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Handle poor network conditions @nisrulz #droidconDE

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Handle poor network conditions Acknowledge unreliable network exists @nisrulz #droidconDE

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Handle poor network conditions Acknowledge unreliable network exists Batch network calls @nisrulz #droidconDE

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Handle poor network conditions Acknowledge unreliable network exists Batch network calls Prefetch data ahead of time @nisrulz #droidconDE

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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

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Implementation/api VS compile Before Gradle 4.0 compile Gradle 4.0+ onwards implementation api @nisrulz #droidconDE

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Require min dependencies Keep a check on method count http://www.methodscount.com/plugins @nisrulz #droidconDE

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Require min dependencies Let the app developer make the decision about inclusion @nisrulz #droidconDE

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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

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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

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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

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Lifecycle Arch Components @nisrulz #droidconDE

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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

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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

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Do not hog the startup @nisrulz #droidconDE

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Do not hog the startup @nisrulz #droidconDE

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Do not hog the startup You do not need to initialize everything, @nisrulz #droidconDE

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Do not hog the startup You do not need to initialize everything, Try to do lazy initialization @nisrulz #droidconDE

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Remove functionality gracefully /** * @deprecated As of release 2.0, replaced by {@link #getPreferredSize()} */ @Deprecated public Dimension preferredSize() { return getPreferredSize(); } @nisrulz #droidconDE

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Document everything Provide Readme.md @nisrulz #droidconDE

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Document everything Provide Readme.md Include javadocs in code @nisrulz #droidconDE

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Document everything Provide Readme.md Include javadocs in code Bundle a sample app @nisrulz #droidconDE

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Document everything Provide Readme.md Include javadocs in code Bundle a sample app Maintain a changelog http://keepachangelog.com @nisrulz #droidconDE

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Document everything @nisrulz #droidconDE

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License is Important https://choosealicense.com/ @nisrulz #droidconDE

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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

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Versioning Strategy Define a versioning scheme i.e MAJOR.MINOR.PATCH http://semver.org/ @nisrulz #droidconDE

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Versioning Strategy To make 2 versions coexist, release under a new group ID @nisrulz #droidconDE

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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

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Proguard, wait… what? @nisrulz #droidconDE

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Proguard, wait… what? Proguard rules can be shipped in an android library @nisrulz #droidconDE

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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

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Proguard, wait… what? @nisrulz #droidconDE

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Proguard, wait… what? @nisrulz #droidconDE

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Proguard, wait… what? @nisrulz #droidconDE

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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

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Credits Emoji Icons designed by Freepik from Flaticon

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Thank You Q & A twitter.com/ nisrulz github.com/ nisrulz .com

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Things I wish I knew when I started building android SDK/libraries twitter.com/ nisrulz github.com/ nisrulz .com