Yo Dawg! I heard you like Kotlin

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Yo Dawg! I heard you like Kotlin Antonio Leiva

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Menu (hope you’re hungry!) 1. Kotlin instead of Java 2. Kotlin for Gradle files 3. Kotlin for views 4. KOTLIN EVERYWHEEAAAR!

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Kotlin instead of Java

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No content

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override fun showAlbum(albumDetail: AlbumDetail?) { if (albumDetail != null) { updateAlbumDetail(albumDetail) } else { postponeTransitions() } }

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override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let {album -> updateAlbumDetail(album)} ?: postponeTransitions() }

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override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let {album -> updateAlbumDetail(album)} ?: postponeTransitions() }

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override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let { updateAlbumDetail(albumDetail) } ?: postponeTransitions() }

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override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let { updateAlbumDetail(it) } ?: postponeTransitions() }

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override fun showAlbum(albumDetail: AlbumDetail?) { albumDetail?.let(this::updateAlbumDetail) ?: postponeTransitions() }

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private fun makeStatusBarTransparent() { supportsLollipop { window.setFlags(FLAG_TRANSLUCENT_STATUS, FLAG_TRANSLUCENT_STATUS) } }

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inline fun supportsLollipop(code: () -> Unit) { if (Build.VERSION.SDK_INT >= 21) { code.invoke() } }

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ui.listCard.animate().alpha(transparent) .setListener(object : AnimatorListenerAdapter() { override fun onAnimationEnd(animation: Animator?) { supportFinishAfterTransition() } })

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inline fun ViewPropertyAnimator.onAnimationEnd( crossinline continuation: (Animator) -> Unit) { setListener(object : AnimatorListenerAdapter() { override fun onAnimationEnd(animation: Animator) { continuation(animation) } }) }

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ui.listCard.animate().alpha(transparent) .onAnimationEnd { supportFinishAfterTransition() }

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Kotlin instead of Java - Verdict

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https://antonioleiva.com

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Kotlin for Gradle files

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Kotlin DSL - Pros

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Kotlin DSL - Cons ● Not easy to configure ● Knowledge about plugin structure ● Not much documentation or examples

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Kotlin DSL - Steps 1. Rename Gradle files 2. Write the config file 3. Convert and compile little by little

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1. Rename Gradle Files .kts

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2. Write the config file plugins { `kotlin-dsl` }

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2. Write the config file class ProjectConfiguration { val buildPlugins = BuildPlugins() val android = Android() val libs = Libs() val testLibs = TestLibs() }

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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" }

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3. Convert and compile little by little val config = ProjectConfiguration() ... dependencies { classpath(config.buildPlugins.androidGradle) classpath(config.buildPlugins.kotlinGradlePlugin) }

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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 }

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Kotlin DSL - Verdict

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Kotlin DSL

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Kotlin for views

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Anko Layouts verticalLayout { val user = editText { hint = "Username" } val pass = editText { hint = "Password" } button("Login") { setOnClickListener { longToast("${user.text}, ${pass.text}") } } }

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Anko Layouts

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Anko Layouts - Pros ● 4x faster ● Better composability ● Easier data binding, complex calculations

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Anko Layouts - Cons ● Lack of designer ● Learn again from scratch ● Some things are more complex (like styles)

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Anko Layouts recycler = autoFitRecycler() .apply(AutofitRecyclerView::style) .lparams(matchParent, matchParent) { behavior = AppBarLayout.ScrollingViewBehavior() }

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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

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Anko Layouts recycler = autoFitRecycler() .apply(AutofitRecyclerView::style) .lparams(matchParent, matchParent) { behavior = AppBarLayout.ScrollingViewBehavior() }

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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))) }

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Anko Layouts - styling .applyRecursively { view -> when (view) { is EditText -> view.textSize = 18f } }

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Anko Layouts recycler = autoFitRecycler() .apply(AutofitRecyclerView::style) .lparams(matchParent, matchParent) { behavior = AppBarLayout.ScrollingViewBehavior() }

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Anko Layouts - Verdict

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Anko Layouts

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KOTLIN EVERYWHEEAAAR!

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Multi-platform projects (Kotlin 1.2) Common Kotlin

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Multi-platform projects (Kotlin 1.2) Common Android Kotlin

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Multi-platform projects (Kotlin 1.2) Common Android Web Kotlin JS

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Multi-platform projects (Kotlin 1.2) Common Android Server Kotlin Web

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Multi-platform projects (Kotlin 1.2) Common Android Server Web iOS Kotlin/Native

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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 }