Yo Dawg! I heard you like Kotlin

Kotlin is the new official language to develop Android Apps, and it can be used almost everywhere.

But did you know you could write a complete App without using other language rather than Kotlin? It can substitute Java in your code, XML in your views and Groovy in your Gradle files.

Transcript

1. Yo Dawg! I heard you like Kotlin Antonio Leiva
2. Menu (hope you’re hungry!) 1. Kotlin instead of Java 2. Kotlin for Gradle files 3. Kotlin for views 4. KOTLIN EVERYWHEEAAAR!
3. Kotlin instead of Java
5. override fun showAlbum(albumDetail: AlbumDetail?) { if (albumDetail != null) { updateAlbumDetail(albumDetail) } else { postponeTransitions() } }
6. override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let {album -> updateAlbumDetail(album)} ?: postponeTransitions() }
7. override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let {album -> updateAlbumDetail(album)} ?: postponeTransitions() }
8. override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let { updateAlbumDetail(albumDetail) } ?: postponeTransitions() }
9. override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let { updateAlbumDetail(it) } ?: postponeTransitions() }
10. override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let(this::updateAlbumDetail) ?: postponeTransitions() }
11. private fun makeStatusBarTransparent() { supportsLollipop { window.setFlags(FLAG_TRANSLUCENT_STATUS, FLAG_TRANSLUCENT_STATUS) } }
12. inline fun supportsLollipop(code: () -> Unit) { if (Build.VERSION.SDK_INT >= 21) { code.invoke() } }
13. ui.listCard.animate().alpha(transparent) .setListener(object : AnimatorListenerAdapter() { override fun onAnimationEnd(animation: Animator?) { supportFinishAfterTransition() } })
14. inline fun ViewPropertyAnimator.onAnimationEnd( crossinline continuation: (Animator) -> Unit) { setListener(object : AnimatorListenerAdapter() { override fun onAnimationEnd(animation: Animator) { continuation(animation) } }) }
15. ui.listCard.animate().alpha(transparent) .onAnimationEnd { supportFinishAfterTransition() }
16. Kotlin instead of Java - Verdict
17. https://antonioleiva.com
18. Kotlin for Gradle files
19. Kotlin DSL - Pros
20. Kotlin DSL - Cons • Not easy to configure • Knowledge about plugin structure • Not much documentation or examples
21. Kotlin DSL - Steps 1. Rename Gradle files 2. Write the config file 3. Convert and compile little by little
22. 1. Rename Gradle Files .kts
23. 2. Write the config file plugins { `kotlin-dsl` }
24. 2. Write the config file class ProjectConfiguration { val buildPlugins = BuildPlugins() val android = Android() val libs = Libs() val testLibs = TestLibs() }
25. 2. Write the config file class Android { val buildToolsVersion = "26.0.2" val minSdkVersion = 19 val targetSdkVersion = 26 val compileSdkVersion = 26 val applicationId = "com.antonioleiva.bandhookkotlin" val versionCode = 1 val versionName = "0.1" }
26. 3. Convert and compile little by little val config = ProjectConfiguration() ... dependencies { classpath(config.buildPlugins.androidGradle) classpath(config.buildPlugins.kotlinGradlePlugin) }
27. 3. Convert and compile little by little defaultConfig { 1. applicationId = config.android.applicationId 2. minSdkVersion(config.android.minSdkVersion) 3. targetSdkVersion(config.android.targetSdkVersion) 4. versionCode = config.android.versionCode 5. versionName = config.android.versionName }
28. Kotlin DSL - Verdict
29. Kotlin DSL
30. Kotlin for views
31. Anko Layouts verticalLayout { val user = editText { hint = "Username" } val pass = editText { hint = "Password" } button("Login") { setOnClickListener { longToast("${user.text}, ${pass.text}") } } }
32. Anko Layouts
33. Anko Layouts - Pros • 4x faster • Better composability • Easier data binding, complex calculations
34. Anko Layouts - Cons • Lack of designer • Learn again from scratch • Some things are more complex (like styles)
35. Anko Layouts recycler = autoFitRecycler() .apply(AutofitRecyclerView::style) .lparams(matchParent, matchParent) { behavior = AppBarLayout.ScrollingViewBehavior() }
36. fun ViewManager.autoFitRecycler(theme: Int = 0) = autoFitRecycler(theme) {} inline fun ViewManager.autoFitRecycler(theme: Int = 0, init: AutofitRecyclerView.() -> Unit) = ankoView(::AutofitRecyclerView, theme, init) Anko Layouts - Custom views
37. Anko Layouts recycler = autoFitRecycler() .apply(AutofitRecyclerView::style) .lparams(matchParent, matchParent) { behavior = AppBarLayout.ScrollingViewBehavior() }
38. Anko Layouts - styling fun AutofitRecyclerView.style() { clipToPadding = false columnWidth = dimen(R.dimen.column_width) scrollBarStyle = View.SCROLLBARS_OUTSIDE_OVERLAY horizontalPadding = dimen(R.dimen.recycler_spacing) verticalPadding = dip(2) addItemDecoration(PaddingItemDecoration(dip(2))) }
39. Anko Layouts - styling .applyRecursively { view -> when (view) { is EditText -> view.textSize = 18f } }
40. Anko Layouts recycler = autoFitRecycler() .apply(AutofitRecyclerView::style) .lparams(matchParent, matchParent) { behavior = AppBarLayout.ScrollingViewBehavior() }
41. Anko Layouts - Verdict
42. Anko Layouts
43. KOTLIN EVERYWHEEAAAR!
44. Multi-platform projects (Kotlin 1.2) Common Kotlin
45. Multi-platform projects (Kotlin 1.2) Common Android Kotlin
46. Multi-platform projects (Kotlin 1.2) Common Android Web Kotlin JS
47. Multi-platform projects (Kotlin 1.2) Common Android Server Kotlin Web
48. Multi-platform projects (Kotlin 1.2) Common Android Server Web iOS Kotlin/Native
49. Multi-platform projects (Kotlin 1.2) expect class MyClass { fun foo(): String fun bar(): Int } actual class MyClass { fun foo(): String = “” fun bar(): Int = 20 }
50. Multi-platform projects (Kotlin 1.2)