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Our Journey from Java to
Kotlin-first!
Pablo Guardiola
@Guardiola31337
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Navigation SDK 1.0
- Kotlin-first
- Modularized
- Clean and performant
APIs that are hard to
misuse
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Episode 1.
Kotlin
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SDKs
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SIZE
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SIZE
& Number of methods
Too many field references: max is 65536
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Show me the
numbers!!!
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Kotlin stdlib increased the
apk size by around 380 KB and
added around 6K methods
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Nope.
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Benefits
Developer
- Intuitive
- Statically typed
- Type inference
- Outstanding IDE support
- Functional and
object-oriented
- Expressive
- Concise
- null safe
- //.
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Client / User
- More strongly typed
than Java
- DSLs
- Modern, powerful and
safe
- Fewer methods, less
weight
Benefits
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Nope.
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30.5%
SDK / Libraries
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77%
Extension
functions
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Nope.
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Nope.
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Navigation SDK
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YES
- Still in Beta (0.x)
- Young
- Client apps in Kotlin
- Excitement
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All in on Kotlin
or not?
Sep 2019
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NO
- stdlib adds binary size
- Kotlin versions
incompatibility
- Extra effort to make
APIs Java friendly
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YES
- Google’s preferred
language for Android
- Productivity
- New Java features
adoption is slow
- OkHttp (v4.x)
- Concurrency
- Hiring
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Oct 8, 2019
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Episode 2.
Conversion
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Code style
ktlint
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@NonNull and @Nullable
annotations
Analyze > Infer Nullity//.
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Convert Java to
Kotlin
⌥⇧⌘K
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Polish Kotlin code
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if null else / let Elvis operator
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if null else / let Elvis operator
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switch / when
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switch / when
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callback
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callback
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Utils
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Special
attention
- /!
- lateinit / lazy
- @NotNull non-annotated
parameters
- @JvmStatic and @get:
- @throws methods
- Writing Java in Kotlin
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MockK
- relaxed = true
RETURNS_DEEP_STUBS
- relaxedUnitFun = true
- Kotlin idiomatic
- mockkObject
- mockkStatic
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Episode 3.
1.0
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Public APIs
- Don’t expose Kotlin
types
- Great for both Java and
Kotlin
- Java and Kotlin
examples
- Master @Jvm annotations
- Rest of the code
internal
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To be continued//.
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Takeaways
- El que la sigue la
consigue (Keep
insisting)
- Baby steps
- Test harness
- Watch out null checks
- Designing Good APIs is
hard
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Thanks.
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Questions?
Pablo Guardiola
@Guardiola31337
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Sources
https://realm.io/realm-report/2017-q4/
https://pusher.com/state-of-kotlin
https://developer.squareup.com/blog/okio-2
https://mockk.io/