10-ish Things about Android Library Development

@zmarkan Zan Markan @zmarkan LIBRARY DEVELOPMENT 10-ish things about Android

@zmarkan @zmarkan Developer tools company blog.pusher.com Chat API Hiring in
Shoreditch Trusted by 150k+ devs pusher.com | @pusher

@zmarkan Contents of this talk • Libs 101 • API
Design • Development & Testing • Releasing • Docs ...and more!

@zmarkan We libs because... Avoid duplicating logic - Best Practice
Sharing == Caring It’s a great way to enrich your We want to be paid

@zmarkan Libraries are a collection of classes and methods that
encapsulate common, shared functionality.

@zmarkan Libs != Apps Libraries are NOT end products Smaller,
more lightweight than apps Many x Many apps/lib ratio

@zmarkan All about that Lib... What: Libraries, Frameworks, SDKs Type:
General libs, UI Widgets, Serverside, Testing Access: Publicly vs Privately accessible Pricing: FOSS, Free to use vs Commercial API: DSL, Reactive, n other things...

@zmarkan Product is about the User • Developers (like you
and I) • Varied backgrounds, levels of experience • User experience -> Developer experience

@zmarkan the truth about developers Library users are Developers… …
developers are very lazy, so... libraries should enable laziness.

@zmarkan API

@zmarkan The API is to a library what the USER
INTERFACE is to an APP

@zmarkan Things I mean by API Entry points Interaction points
Data model Errors & Exceptions

@zmarkan Entry points (where people first interact with your code)
They allow you to instantiate and configure the library In “Code”: Constructors, Builders, Factories In UI: Widgets

@zmarkan Builder Poor person’s named args … and optional args
Ensures constructor is passed correct values, and validates its state before building the class

@zmarkan Building the - Static inner class - … called
Builder - setters mutate its state, returning this - build() constructs the main object - build() validates the view state AS SEEN IN RETROFIT

@zmarkan Methods & Models When in doubt - go S.O.L.I.D.
Naming, Naming, Naming! Don’t surprise your users! (But you can delight them)

@zmarkan (R)X-Factor Aysnc as a stream of events Allows chaining,
and functional operations Support all the things: RxSwift, RxJava (even PHP!) More: Paco Estevez makes AWESOME Rx libs/articles/talks

@zmarkan RX in brief observable .filter(//condition) .flatMap(//transformation) .subscribe(//handleSuccess, //handleError) Not
shown: one million operators, threading, ...

@zmarkan RX… but It’s still a power user feature Callbacks
are still often preferred provide RX adapter as an optional extra?

@zmarkan for the λ Consider functional interfaces ...they can be
replaced with lambdas easily Used with Retrolambda, Kotlin, Java 8 Power users tend to like them. Be nice to your power users.

@zmarkan @nnotations Add validation features - NotNull, Nullable Value types
- AutoValue, AutoParcel Build Annotations to write code for you Use Square/JavaPoet More: Jason Feinstein’s talk from CodeMotion Tel Aviv 2016

@zmarkan DSL-o-Matic 9000 Make your own little programming language… ...by
inventing a syntax that works for you! Examples: Hamcrest, Rx, Kotlin Anko Techniques: Annotations, Operator overloading, Extension methods, ...

@zmarkan When things go • Let it crash! • Early
• Often Ensure the error messaging is spot on Add links in error messages to explanations

@zmarkan Anatomy of a “nice” Error Type: Illegal Input Message:
Request unsuccessful, reason: malformed auth token Link: https://example.com/errors/123456 Explain things here!

@zmarkan DEV & TEST

@zmarkan Performance or Be wary of: • Library size =>
App size • Memory leaks • Build times • Needless dependencies

@zmarkan ...my lib ain’t one! - Avoid private fields in
parent classes - Prefer anonymous inner classes to lambdas - Avoid needless dependencies (again) - Proguard rules More: Jake Wharton’s talk from 360AnDev I got 65k problems, but...

@zmarkan API should be beautiful. Implementation should f*****g work.

@zmarkan Testing it & Loving it The easy: Unit Tests
The hard: Integration Tests with an app The smart: fooding More in: David Schreiber-Ranner’s talk from Droidcon Vienna 2016

@zmarkan Tracking & Analysis Problem: No Google Analytics for libraries
Track at the service level? Listen and talk to users fooding: Redux unless you’re Fabric

@zmarkan

@zmarkan (Semantic) Versioning 2.0 Major[.]Minor[.]Patch • Major: Breaking changes •
Minor: New features • Patch: Hotfixes Shouldn’t ever happen • semver.org

@zmarkan Releasing (how not to do it) • Manually include
the JAR/AAR in your project (Bad idea in most cases) • Include project as a Git submodule (Even worse idea in all cases)

@zmarkan Releasing (the right way) Maven Central JCenter Jitpack Artifactory
Maven dir on S3 Managed services free for OSS More DIY just add server

@zmarkan DOCS

@zmarkan 50 shades of Docs • Quick Start • Sample
apps • JavaDoc • Wiki pages • Yes, even tests! • Mix & Match!

@zmarkan Quickstart a.k.a. “Let me copypaste something”

@zmarkan Sample code • Should be small, confined apps •
… often alongside libraries in the same repo • Should reflect your libraries’ features • Can go in-depth for more advanced features

@zmarkan JavaDoc • Cheap to make • Automagically generated •
(Just add comments!) • Great in Android Studio • Host it alongside your other docs

@zmarkan Libraries enable app developers to be lazy. Docs enable
library developers to be lazy.

@zmarkan The takeaways Libs 101 API design Development Releasing Support

@zmarkan @zmarkan fin Blog: www.spacecowboyrocketcompany.com Twitter: @zmarkan Github: @zmarkan Email:
zan@[pusher.com | markan.me]

10-ish Things about Android Library Development

10-ish Things about Android Library Development

More Decks by Zan Markan

Other Decks in Programming

Featured

Transcript