some code stories

Scala expressiveness strikes back !

A sample showing iteration between scala actors and android.Activity

Extending activity with a trait  to receive events from another actors, services, or any other source ( listeners , as a observer … )

class MainActivity extends Activity
                      with ActivityUtil
                      with Reactive { 

    override def onCreate(savedInstanceState: Bundle) {
        super.onCreate(savedInstanceState) 

        setContentView(R.layout.main) 

        button(R.id.Button01).onClicked {
            app.actor ! Ping(this)
        }
    } 

    onReact {
        case Pong(count) => onUi {
            textView(R.id.Label1).setText("Pong -> " + count)
        }
    }
} 

Isn’t she pretty ?

1. ActivityUtil
   • Allow us to access activity components directly

     
     button(R.id.Button01)

2. Reactive
   • Converts the activity into a scala actor
   • Calling onReact with the desired partialFunctions, allow us to manage the external events

     
     onReact {
         case Pong(count) => onUi {
             textView(R.id.Label1).setText("Pong -> " + count)
         }
     } 

     One problem, onReact resides inside another thread ( the actor one ), so to access components of the view, we must use onUi function

3. ViewConversions
   • With a bunch of implicit conversions, we can implement Listeners directly with functions

     
     button(R.id.Button01).onClicked {
         app.actor ! Ping(this)
     } 

4. The application class contains the other actor who returns Pong

   
   
   class App extends Application {
       val actor = new SampleActor 
   
       override def onCreate(): Unit = {
           actor.start
       }
   } 
   
   case class Pong(count: Int)
   case class Ping(a: Actor) 
   
   class SampleActor extends Actor with L {
       private var count = 0
       def act() {
           loop {
               receive {
                   case Ping(a) => {
                       count = count + 1
                       a ! Pong(count)
                   }
               }
           }
       }
   }
   

I just remembered why I love scala so much

PD: I used giter8 to get a scala-android template

 g8 gseitz/android-sbt-project 

• giter8  https://github.com/n8han/giter8
• template home https://github.com/gseitz/android-sbt-project.g8
• scala-home http://www.scala-lang.org/
• sample-code https://github.com/jgoday/sample_android_scala_actor