Scala on Android - The current state of affairs

An overview of the current state of affairs when developing Android apps with Scala, and examine why contrary to popular belief it is ready for prime time. We will discover some of the tools and more useful libraries, and explore how Scala on Android helps circumvent most of the limitations of Java and the Android SDK

Transcript

1. (Scala on Android) 㱺 The current state of affairs 1
   

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2. whoami
   㱺 CTO & Co-Founder at 47 Degrees, a global
   consulting agency & Typesafe Consulting Partner.
   @raulraja
   @47deg
   http://47deg.com/blog
   (Scala on Android) 㱺 The current state of affairs 2
   

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3. Build Tools
   (Scala on Android) 㱺 The current state of affairs 3
   

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4. SBT 㱺 Android SDK Plugin
   https://github.com/pfn/android-sdk-plugin
   (Scala on Android) 㱺 The current state of affairs 4
   

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5. SBT 㱺 Android SDK Plugin
   — Supports all Android SDK tasks
   — dex
   — typedResourcesGenerator
   — proguard
   — buildConfigGenerator
   — (+ 20... more)
   (Scala on Android) 㱺 The current state of affairs 5
   

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6. SBT 㱺 Android SDK Plugin 㱺 typedResourcesGenerator
   object TR {
   val title = TypedResource[TextView](R.id.title)
   object layout {
   val abc_screen_toolbar = TypedLayout[ActionBarOverlayLayout](R.layout.abc_screen_toolbar)
   }
   }
   class MyActivity extends TypedActivity {
   val titleTextView = findView(title) //titleTextView inferred as TextView, no casting needed
   }
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7. SBT 㱺 Android SDK Plugin 㱺 proguard
   Size Matters
   Scala byte code size reduced ~ (2.8M)
   (Scala on Android) 㱺 The current state of affairs 7
   

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8. SBT 㱺 Android SDK Plugin
   — https://github.com/pfn/android-sdk-plugin
   — Active
   — Fast (incremental compilation and proguard
   caching)
   — Proguard + MultiDexApplication integration
   (Circumvents 65K method limit)
   — Supports AAR, JAR and APK artifact types
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9. IDE Support
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10. IntelliJ IDEA 㱺 Syntax Highlighting
    (Scala on Android) 㱺 The current state of affairs 10
    

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11. IntelliJ IDEA 㱺 Android + Scala + SBT
    (Scala on Android) 㱺 The current state of affairs 11
    

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12. IntelliJ IDEA
    — Active
    — Syntax Highlighting
    — Code assistance
    — Android Studio : Based on IntelliJ
    > Google says: If you have been using Eclipse
    with ADT, be aware that Android Studio is now the
    official IDE for Android
    (Scala on Android) 㱺 The current state of affairs 12
    

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13. Libraries
    (Scala on Android) 㱺 The current state of affairs 13
    

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14. Libraries 㱺 Scaloid 㱺 Simplifying the Android SDK
    //plain vanilla scala
    val button = new Button(context)
    button.setText("Greet")
    button.setOnClickListener(new OnClickListener() {
    def onClick(v: View) {
    Toast.makeText(context, "Hello!", Toast.LENGTH_SHORT).show()
    }
    })
    layout.addView(button)
    (Scala on Android) 㱺 The current state of affairs 14
    

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15. Libraries 㱺 Scaloid 㱺 Simplifying the Android SDK
    //with Scaloid
    SButton("Greet", toast("Hello!"))
    (Scala on Android) 㱺 The current state of affairs 15
    

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16. Libraries 㱺 Scaloid 㱺 XML-less layouts
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content" android:padding="20dip">
    android:layout_height="wrap_content" android:text="Sign in"
    android:layout_marginBottom="25dip" android:textSize="24.5sp"/>
    android:layout_height="wrap_content" android:text="ID"/>
    android:layout_height="wrap_content" android:id="@+id/userId"/>
    android:layout_height="wrap_content" android:text="Password"/>
    android:layout_height="wrap_content" android:id="@+id/password"
    android:inputType="textPassword"/>
    android:layout_height="wrap_content" android:id="@+id/signin"
    android:text="Sign in"/>
    
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17. Libraries 㱺 Scaloid 㱺 XML-less layouts
    //with scaloid
    new SVerticalLayout {
    STextView("Sign in").textSize(24.5 sp).<<.marginBottom(25 dip).>>
    STextView("ID")
    SEditText()
    STextView("Password")
    SEditText() inputType TEXT_PASSWORD
    SButton("Sign in")
    }.padding(20 dip)
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18. Libraries 㱺 Scaloid 㱺 Futures & Async
    //plain scala
    new AsyncTask[String, Void, String] {
    def doInBackground(params: Array[String]) = {
    doAJobTakeSomeTime(params)
    }
    override def onPostExecute(result: String) {
    alert("Done!", result)
    }
    }.execute("param")
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19. Libraries 㱺 Scaloid 㱺 Futures & Async
    //scaloid
    Future {
    val result = doAJobTakeSomeTime(params)
    runOnUiThread(alert("Done!", result))
    }
    (Scala on Android) 㱺 The current state of affairs 19
    

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20. Libraries 㱺 Macroid 㱺 Functional UI with Macros
    import macroid._
    import macroid.FullDsl._
    class GreetingActivity extends Activity with Contexts[Activity] {
    override def onCreate(savedInstanceState: Bundle) = {
    super.onCreate(savedInstanceState)
    // the layout goes here
    setContentView {
    getUi {
    l[LinearLayout](
    w[Button],
    w[TextView]
    )
    }
    }
    }
    }
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21. Libraries 㱺 Macroid 㱺 UI composition
    // ActivityContext is an Android Context obtained from an Activity
    import macroid.ActivityContext
    ...
    def layout1(implicit ctx: ActivityContext) =
    l[LinearLayout](
    w[TextView]
    )
    def layout2(implicit ctx: ActivityContext) =
    l[FrameLayout](
    w[ProgressBar]
    )
    def layout3(implicit ctx: ActivityContext) =
    l[FrameLayout](
    layout1,
    layout2
    )
    ...
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22. Libraries 㱺 Macroid 㱺 Tweaks
    l[LinearLayout](
    // set button caption
    w[Button] <~ text("Click me"),
    // set text and hide for the time being
    w[TextView] <~ text("Hello!") <~ hide
    // set layout orientation
    ) <~ vertical
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23. Libraries 㱺 Macroid 㱺 Tweaks Composition
    // AppContext is an Android Context obtained from getApplicationContext
    import macroid.AppContext
    // More tweaks
    import macroid.contrib.TextTweaks
    def greeting(greeting: String)(implicit appCtx: AppContext) =
    TextTweaks.large +
    text(greeting) +
    hide
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24. Libraries 㱺 Macroid 㱺 Events
    button <~ On.click {
    ...
    }
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25. Libraries 㱺 Macroid 㱺 Slots
    // create a slot
    var greeting = slot[TextView]
    l[LinearLayout](
    w[TextView] <~
    // wire the view to the slot
    wire(greeting) <~
    OurTweaks.greeting("Hello!"),
    w[Button] <~
    text("Click me") <~
    On.click {
    // use the slot elsewhere
    greeting <~ show
    }
    ) <~ vertical
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26. Libraries 㱺 Macroid 㱺 Contexts
    class MyActivity extends Activity with Contexts[Activity] {
    // implicit access to AppContext & ActivityContext stored as a weak reference
    }
    class MyFragment extends Fragment with Contexts[Fragment] {
    // implicit access to AppContext & ActivityContext stored as a weak reference
    }
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27. Libraries 㱺 Macroid 㱺 Contexts
    class MyActivity extends Activity with Contexts[Activity] {
    // implicit access to AppContext & ActivityContext stored as a weak reference
    }
    class MyFragment extends Fragment with Contexts[Fragment] {
    // implicit access to AppContext & ActivityContext stored as a weak reference
    }
    No need to explicitly pass the context around!
    (Scala on Android) 㱺 The current state of affairs 27
    

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28. Libraries 㱺 Macroid 㱺 Snails
    val focusLoudly = Snail[View] { view 㱺
    view.setFocus()
    playSound
    }
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29. Libraries 㱺 Macroid 㱺 Snails composition
    val wink = fadeIn ++ fadeOut
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30. Libraries 㱺 Macroid 㱺 Snails & Tweaks combined
    editText <~ text("foo") <~~ fadeIn <~ enable
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31. Libraries 㱺 Macroid 㱺 Easy workflows
    (myProgressBar <~~ fadeOut(400)) ~~
    (myTextView <~~ blink) ~~
    (myOtherTextView <~ text("’Scala at the Sea!"))
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32. Libraries 㱺 Macroid 㱺 Transformers
    linearLayout <~ Transformer {
    case t: TextView 㱺 t <~ text("foo")
    case i: ImageView 㱺 i <~ hide
    }
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33. Libraries 㱺 Macroid 㱺 Adaptive (Media queries)
    object OurTweaks {
    def orient(implicit appCtx: AppContext) =
    landscape ? horizontal | vertical
    }
    ...
    // in layout
    l[LinearLayout](
    ...
    ) <~ OurTweaks.orient
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34. Libraries 㱺 Macroid 㱺 Viewable
    Brings the power of Typeclasses to UI composition.
    How to display A using W.
    libraryDependencies += aar("org.macroid" %% "macroid-viewable" % "2.0.0-M3")
    trait Viewable[A, +W <: View]
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35. Libraries 㱺 Macroid 㱺 Viewable
    import macroid.viewable.Viewable
    case class User(name: String)
    def userViewable(
    implicit ctx: ActivityContext,
    appCtx: AppContext): Viewable[User, TextView] =
    Viewable[User] { user 㱺
    w[TextView] <~ TextTweaks.large <~ text(user.name)
    }
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36. Libraries 㱺 Macroid 㱺 Akka Fragments
    Handling Fragment events & messaging with Actors.
    class MyActor extends FragmentActor[MyFragment] {
    def receive = receiveUi andThen {
    case MyMessage(x) 㱺 ...
    case MyOtherMessage 㱺 withUi(fragment 㱺 Ui {
    // do some cool ui stuff here
    })
    case FragmentActor.AttachUi(_) 㱺 ...
    case FragmentActor.DetachUi(_) 㱺 ...
    }
    }
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37. OS Apps 㱺 Translate Bubble
    https://play.google.com/store/apps/details?id=com.fortysevendeg.translatebubble
    https://github.com/47deg/translate-bubble-android
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38. OS Apps 㱺 Scala Days Official App
    https://play.google.com/store/apps/details?id=com.fortysevendeg.android.scaladays
    https://github.com/47deg/scala-days-android
    (source code available on March 15th)
    (Scala on Android) 㱺 The current state of affairs 38
    

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39. OS Apps 㱺 Scala API Demos
    https://play.google.com/store/apps/details?id=com.fortysevendeg.scala.android
    https://github.com/47deg/scala-android
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40. Thank you
    @raulraja
    @47deg
    raul at 47deg.com
    http://47deg.com/blog
    https://speakerdeck.com/raulraja/scala-on-android-the-current-state-of-
    affairs
    https://github.com/47deg/scala-on-android-deck
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