Painless Android Development with Scala

A joint talk with @javielinux about #Scala as an alternative for better #Android Development where some common android development pitfalls are shown and how they can be solved with Scala.

Transcript

1. (Scala on Android) 㱺 Painless Android Development with Scala 1
   

   View Slide

2. 㱺 47 Degrees, a global consulting agency & Typesafe
   Consulting Partner.
   @raulraja
   @javielinux
   @47deg
   http://47deg.com/blog
   (Scala on Android) 㱺 Painless Android Development with Scala 2
   

   View Slide

3. Build Tools
   (Scala on Android) 㱺 Painless Android Development with Scala 3
   

   View Slide

4. SBT 㱺 Android SDK Plugin
   https://github.com/pfn/android-sdk-plugin
   (Scala on Android) 㱺 Painless Android Development with Scala 4
   

   View Slide

5. SBT 㱺 Android SDK Plugin
   — Supports all Android SDK tasks
   — dex
   — typedResourcesGenerator
   — proguard
   — buildConfigGenerator
   — (+ 20... more)
   (Scala on Android) 㱺 Painless Android Development with Scala 5
   

   View Slide

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 AppCompatActivity with TypedActivity {
   val titleTextView = findView(title) //titleTextView inferred as TextView, no casting needed
   }
   (Scala on Android) 㱺 Painless Android Development with Scala 6
   

   View Slide

7. SBT 㱺 Android SDK Plugin 㱺 proguard
   Size Matters
   Scala byte code size reduced ~ (2.8M)
   (Scala on Android) 㱺 Painless Android Development with Scala 7
   

   View Slide

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
   (Scala on Android) 㱺 Painless Android Development with Scala 8
   

   View Slide

9. Java Vs Scala 㱺 NullPointerExceptions
   Person person = getPerson();
   String name = null;
   if (person != null && person.getJob() != null) {
   name = person.getJob().getName();
   }
   if (name != null) {
   return name;
   } else {
   return DEFAULT_NAME;
   }
   (Scala on Android) 㱺 Painless Android Development with Scala 9
   

   View Slide

10. Java Vs Scala 㱺 NullPointerExceptions
    val jobName : Option[String] = person.job map (_.name)
    OR
    val jobName : Option[String] = for {
    job <- person.job
    } yield job.name
    OR
    Option, Try, Either, \/, Validation
    (Scala on Android) 㱺 Painless Android Development with Scala 10
    

    View Slide

11. Java Vs Scala 㱺 Contexts
    public class MainActivity
    extends Activity {
    public void bar() {
    FooUtils.get(getContext(), R.string.name);
    }
    }
    public class FooUtils {
    static String get(Context c, int res) {
    return c.getString(res);
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 11
    

    View Slide

12. Java Vs Scala 㱺 Contexts
    class MainActivity extends Activity {
    implicit val ctx = getApplicationContext
    def bar = FooUtils.get(R.string.name)
    }
    object FooUtils {
    def get(res : Int)(implicit ctx : Context) = {
    ctx.getString(res)
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 12
    

    View Slide

13. Java Vs Scala 㱺 Contexts
    trait Contexts { self : Activity =>
    implicit val appContext = getApplicationContext
    implicit val activityContext = this
    }
    class MainActivity extends Activity with Contexts {
    def bar = FooUtils.get(R.string.name)
    }
    object FooUtils {
    def get(res : Int)(implicit ctx : Context) = {
    ctx.getString(res)
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 13
    

    View Slide

14. Java Vs Scala 㱺 Implicit Classes
    public class TextViewUtils {
    public void loadFont(TextView textView, String font) {
    textView.setFontType(font,...)
    }
    }
    TextViewUtils.loadFont(textView, "robotto");
    (Scala on Android) 㱺 Painless Android Development with Scala 14
    

    View Slide

15. Java Vs Scala 㱺 Implicit Classes
    object Helpers {
    implicit class TextViewHelpers(textView: TextView) {
    def loadFont(font: String) = ???
    }
    }
    import Helpers._
    textView.loadFont(“Roboto.ttf”)
    (Scala on Android) 㱺 Painless Android Development with Scala 15
    

    View Slide

16. Java Vs Scala 㱺 Async
    public class MyTask1 extends AsyncTask {
    protected Integer doInBackground(Void... v) {
    return r1;
    }
    protected void onPostExecute(Integer result) {
    new MyTask2().execute(result);
    }
    }
    public class MyTask2 extends AsyncTask {
    protected Integer doInBackground(Integer... r1) {
    return r2;
    }
    protected void onPostExecute(Integer result) {
    r1 + r2;
    }
    }
    new MyTask1().execute();
    (Scala on Android) 㱺 Painless Android Development with Scala 16
    

    View Slide

17. Java Vs Scala 㱺 Async
    def myTask1: Future[Int] = Future(1)
    def myTask2: Future[Int] = Future(2)
    def sumResponses: Future[Int] =
    for {
    r1 <- myTaks1
    r2 <- myTaks2
    } yield (r1 + r2)
    sumResponses map println
    (Scala on Android) 㱺 Painless Android Development with Scala 17
    

    View Slide

18. Java Vs Scala 㱺 Async
    Future.reduce(List(Future(1), Future(2))) { (a, b) =>
    a + b
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 18
    

    View Slide

19. Java Vs Scala 㱺 Async
    Future.reduce(List(Future(1), Future(2))) (_ + _)
    (Scala on Android) 㱺 Painless Android Development with Scala 19
    

    View Slide

20. Java Vs Scala 㱺 Models
    public class Person {
    private String name;
    private String lastName;
    public String getName() {
    return name;
    }
    public void setName(String name) {
    this.name = name;
    }
    public String getLastName() {
    return lastName;
    }
    public void setLastName(String lastName) {
    this.lastName = lastName;
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 20
    

    View Slide

21. Java Vs Scala 㱺 Models
    case class Person(
    name : String,
    lastName : String)
    (Scala on Android) 㱺 Painless Android Development with Scala 21
    

    View Slide

22. Java Vs Scala 㱺 Pattern Matching
    public boolean onTouchEvent(MotionEvent ev) {
    ...
    switch (action) {
    case MotionEvent.ACTION_DOWN:
    ...
    break;
    case MotionEvent.ACTION_MOVE:
    ...
    break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_CANCEL:
    ...
    break;
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 22
    

    View Slide

23. Java Vs Scala 㱺 Pattern Matching
    def onTouchEvent(ev: MotionEvent) {
    import MotionEvent._
    action match {
    case ACTION_DOWN => ???
    case ACTION_MOVE => ???
    case ACTION_UP | ACTION_CANCEL => ???
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 23
    

    View Slide

24. Java Vs Scala 㱺 Pattern Matching
    person match {
    case Person(_, lastName) if lastName == “Pacheco” =>
    println(“Guapetón”)
    case Person(name, _) if name == “Raúl” =>
    println(“Resultón”)
    case _ =>
    println(“Programadores Java”)
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 24
    

    View Slide

25. Java Vs Scala 㱺 Singletons
    public class MySingleton {
    private MySingleton(){}
    public synchronized static MySingleton getInstance() {
    if(instance == null) instance = new MySingleton ();
    return instance;
    }
    public void bar(){
    ...
    }
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 25
    

    View Slide

26. Java Vs Scala 㱺 Singletons
    object MySingleton {
    def bar = ...
    }
    (Scala on Android) 㱺 Painless Android Development with Scala 26
    

    View Slide

27. Java Vs Scala 㱺 Mixins
    class Mammal
    class PlatyPus extends Mammal
    new PlatyPus().eggs() <- Compilation Error!!!
    (Scala on Android) 㱺 Painless Android Development with Scala 27
    

    View Slide

28. Java Vs Scala 㱺 Mixins
    trait Mammal
    trait EggsSupport {
    def eggs : Eggs
    }
    class PlatyPus extends Mammal with EggsSupport
    PlatyPus().eggs <- Success!!!
    (Scala on Android) 㱺 Painless Android Development with Scala 28
    

    View Slide

29. OS Apps 㱺 Translate Bubble
    https://play.google.com/store/apps/details?id=com.fortysevendeg.translatebubble
    https://github.com/47deg/translate-bubble-android
    (Scala on Android) 㱺 Painless Android Development with Scala 29
    

    View Slide

30. 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
    (Scala on Android) 㱺 Painless Android Development with Scala 30
    

    View Slide

31. OS Apps 㱺 Scala API Demos
    https://play.google.com/store/apps/details?id=com.fortysevendeg.scala.android
    https://github.com/47deg/scala-android
    (Scala on Android) 㱺 Painless Android Development with Scala 31
    

    View Slide

32. Thank you
    @47deg
    @javielinux
    @raulraja
    http://47deg.com/blog
    https://speakerdeck.com/raulraja/painless-android-development-with-scala-
    deck
    https://github.com/47deg/painless-android-development-with-scala-deck
    (Scala on Android) 㱺 Painless Android Development with Scala 32
    

    View Slide