JavaFX and Scala - Like Milk and Cookies

JavaFX and Scala – Like Milk and Cookies Stephen Chin Luc Duponcheel JavaFX Evangelist, Oracle Independent, ImagineJ steveonjava@gmail.com luc.duponcheel@gmail.com tweet: @steveonjava tweet: @LucDup

Meet the Presenters Stephen Chin Luc Duponcheel Family Man Motorcyclist BeJUG Researcher

JavaFX 2.0 PlatformImmersive Application Experience> Cross-platform Animation, Video, Charting> Integrate Java, JavaScript, and HTML5 in the same application> New graphics stack takes advantage of hardware acceleration for 2D and 3D applications> Use your favorite IDE: NetBeans, Eclipse, IntelliJ, etc.

JavaFXScala 4

JavaFX With Java

JavaFX in Java> JavaFX API uses an enhanced JavaBeans pattern> Similar in feel to other UI toolkits (Swing, Pivot, etc.)> Uses builder pattern to minimize boilerplate

Vanishing Circles 7

Application Skeletonpublic class VanishingCircles extends Application { public static void main(String[] args) { Application.launch(args); } @Override public void start(Stage primaryStage) { primaryStage.setTitle("Vanishing Circles"); Group root = new Group(); Scene scene = new Scene(root, 800, 600, Color.BLACK); [create the circles…] root.getChildren().addAll(circles); primaryStage.setScene(scene); primaryStage.show(); [begin the animation…] }}

Create the CirclesList<Circle> circles = new ArrayList<Circle>();for (int i = 0; i < 50; i++) { final Circle circle = new Circle(150); circle.setCenterX(Math.random() * 800); circle.setCenterY(Math.random() * 600); circle.setFill(new Color(Math.random(), Math.random(), Math.random(), .2)); circle.setEffect(new BoxBlur(10, 10, 3)); circle.setStroke(Color.WHITE); [setup binding…] [setup event listeners…] circles.add(circle);} 9

Setup Bindingcircle.strokeWidthProperty().bind(Bindings .when(circle.hoverProperty()) .then(4) .otherwise(0)); 10

Setup Event Listenerscircle.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() { public void handle(MouseEvent t) { KeyValue collapse = new KeyValue(circle.radiusProperty(), 0); new Timeline(new KeyFrame(Duration.seconds(3), collapse)).play(); }}); 11

Begin the AnimationTimeline moveCircles = new Timeline();for (Circle circle : circles) { KeyValue moveX = new KeyValue(circle.centerXProperty(), Math.random() * 800); KeyValue moveY = new KeyValue(circle.centerYProperty(), Math.random() * 600); moveCircles.getKeyFrames().add(new KeyFrame(Duration.seconds(40), moveX, moveY));}moveCircles.play(); 12

JavaFX With Scala 13

Java vs. Scala DSLpublic class VanishingCircles extends Application { object VanishingCircles extends JFXApp { var circles: Seq[Circle] = null public static void main(String[] args) { stage = new Stage { Application.launch(args); title = "Vanishing Circles" } width = 800 height = 600 @Override scene = new Scene { public void start(Stage primaryStage) { fill = BLACK primaryStage.setTitle("Vanishing Circles"); circles = for (i <- 0 until 50) yield new Circle { Group root = new Group(); centerX = random * 800 Scene scene = new Scene(root, 800, 600, Color.BLACK); centerY = random * 600 List<Circle> circles = new ArrayList<Circle>(); radius = 150 for (int i = 0; i < 50; i++) { fill = color(random, random, random, .2) final Circle circle = new Circle(150); effect = new BoxBlur(10, 10, 3) 40 Lines circle.setCenterX(Math.random() * 800); circle.setCenterY(Math.random() * 600); circle.setFill(new Color(Math.random(), Math.random(), Math.random(), .2)); circle.setEffect(new BoxBlur(10, 10, 3)); 33 Lines strokeWidth <== when (hover) then 4 otherwise 0 stroke = WHITE onMouseClicked = { Timeline(at (3 s) {radius -> 0}).play() 1299 Characters circle.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() { public void handle(MouseEvent t) { KeyValue collapse = new KeyValue(circle.radiusProperty(), 0); } } } 591 Characters content = circles new Timeline(new KeyFrame(Duration.seconds(3), collapse)).play(); } } }); new Timeline { circle.setStroke(Color.WHITE); cycleCount = INDEFINITE circle.strokeWidthProperty().bind(Bindings.when(circle.hoverProperty()) autoReverse = true .then(4) keyFrames = for (circle <- circles) yield at (40 s) { .otherwise(0)); Set( circles.add(circle); circle.centerX -> random * stage.width, } circle.centerY -> random * stage.height root.getChildren().addAll(circles); ) primaryStage.setScene(scene); } primaryStage.show(); }.play(); } Timeline moveCircles = new Timeline(); for (Circle circle : circles) { KeyValue moveX = new KeyValue(circle.centerXProperty(), Math.random() * 800); KeyValue moveY = new KeyValue(circle.centerYProperty(), Math.random() * 600); moveCircles.getKeyFrames().add(new KeyFrame(Duration.seconds(40), moveX, moveY)); } moveCircles.play(); }} 14

object VanishingCircles extends JFXApp { stage = new Stage { title = "Disappearing Circles" width = 800 height = 600 scene = new Scene { fill = BLACK content = for (i <- 0 until 50) yield new Circle { centerX = random * 800 centerY = random * 600 radius = 150 fill = color(random, random, random, 0.2) effect = new BoxBlur(10, 10, 3) } } }} 15

object VanishingCircles extends JFXApp { stage = new Stage { title = "Disappearing Circles" width = 800 height = 600 class for JavaFX Base applications scene = new Scene { fill = BLACK content = for (i <- 0 until 50) yield new Circle { centerX = random * 800 centerY = random * 600 radius = 150 fill = color(random, random, random, 0.2) effect = new BoxBlur(10, 10, 3) } } }} 16

object VanishingCircles extends JFXApp { stage = new Stage { title = "Disappearing Circles" width = 800 height = 600 Declarative Stage scene = new Scene { fill = BLACK definition content = for (i <- 0 until 50) yield new Circle { centerX = random * 800 centerY = random * 600 radius = 150 fill = color(random, random, random, 0.2) effect = new BoxBlur(10, 10, 3) } } }} 17

object VanishingCircles extends JFXApp { stage = new Stage { title = "Disappearing Circles" width = 800 Inline property height = 600 definitions scene = new Scene { fill = BLACK content = for (i <- 0 until 50) yield new Circle { centerX = random * 800 centerY = random * 600 radius = 150 fill = color(random, random, random, 0.2) effect = new BoxBlur(10, 10, 3) } } }} 18

object VanishingCircles extends JFXApp { stage = new Stage { title = "Disappearing Circles" width = 800 Sequence Creation Via height = 600 Loop scene = new Scene { fill = BLACK content = for (i <- 0 until 50) yield new Circle { centerX = random * 800 centerY = random * 600 radius = 150 fill = color(random, random, random, 0.2) effect = new BoxBlur(10, 10, 3) } } }} 19

Binding in ScalaInfix Addition/Subtraction/Multiplication/Division:height <== rect1.height + rect2.heightAggregate Operators:width <== max(rect1.width, rect2.width, rect3.width)Conditional Expressions:strokeWidth <== when (hover) then 4 otherwise 0Compound Expressions:text <== when (rect.hover || circle.hover && !disabled) then textField.text + " is enabled" otherwise "disabled" 20

Animation in Scalaval timeline = new Timeline { cycleCount = INDEFINITE autoReverse = true keyFrames = for (circle <- circles) yield at (40 s) { Set( circle.centerX -> random * stage.width, circle.centerY -> random * stage.height ) }}timeline.play(); 21

JavaFX Script-like animationAnimation in Scala syntax: at (duration) {keyframes}val timeline = new Timeline { cycleCount = INDEFINITE autoReverse = true keyFrames = for (circle <- circles) yield at (40 s) { Set( circle.centerX -> random * stage.width, circle.centerY -> random * stage.height ) }}timeline.play(); 22

Animation in Scalaval timeline = new Timeline { cycleCount = INDEFINITE autoReverse = true keyFrames = for (circle <- circles) yield at (40 s) { Set( circle.centerX -> random * stage.width, circle.centerY -> random * stage.height ) }}timeline.play(); Operator overloading for animation syntax 23

Animation in Scalaval timeline = new Timeline { cycleCount = INDEFINITE autoReverse = true keyFrames = for (circle <- circles) yield at (40 s) { Set( circle.centerX -> random * stage.width tween EASE_BOTH, circle.centerY -> random * stage.height tween EASE_IN ) }}timeline.play(); Optional tween syntax 24

Event Listeners in Scala> Supported using the built-in Closure syntax> Arguments for event objects> 100% type-safe onMouseClicked = { (e: MouseEvent) => Timeline(at(3 s){radius->0}).play() } 25

Event Listeners in Scala> Supported using the built-in Closure syntax> Arguments for event objects Optional event> 100% type-safe parameter {(event) => body} onMouseClicked = { (e: MouseEvent) => Timeline(at(3 s){radius->0}).play() } 26

Jumping Frogs PuzzleImage by renwest: http://www.flickr.com/photos/19941963@N00/438340463 27

Jumping Frogs Puzzle> My first ScalaFX program> Similar to (but more concise as) my version using JavaFX 1.2> After a few JavaFX 1.2 to ScalaFX translation iterations it just worked> After some MVC rethinking and a few refactoring iterations it worked even better (e.g. it is possible to click on a jumping frog) 28

Applicationobject JumpingFrogsPuzzle extends JFXApp { stage = new Stage { title = TITLE scene = new Scene { content = theShapes.canvasShape :: theShapes.stoneShapes ::: theView.frogShapes } }} 29

Frogtrait Frog { def movesToRight: Boolean def movesToLeft: Boolean}class LeftFrog() extends Frog { def movesToRight = true def movesToLeft = false}class RightFrog() extends Frog { def movesToRight = false def movesToLeft = true} 30

Model (frogMap)var frogMap: Map[Int, Frog] = _private val frogAtPosition = (i: Int) => frogMap(i)val positionOf = (frog: Frog) => (for { (i, `frog`) <- frogMap} yield i) head 31

Model (move)private val move = (next: Int => Int) => (frog: Frog) => frogMap = (for { entry@(_, aFrog) <- frogMap if (aFrog != frog) } yield { entry }) + (next(positionOf(frog)) -> frog) 32

View (jump)private val jump = (length: Int) => (direction: (Double, Double) => Double) => (frogShape: FrogShape) => { // ... Timeline(Seq( at(midTime) { frogShape.centerX -> midCenterX}, at(midTime) { frogShape.centerY -> midCenterY}, at(endTime) { frogShape.centerX -> endCenterX}, at(endTime) { frogShape.centerY -> endCenterY } )).play()} 33

View (control)private val control: Unit => Unit = { _ => view.frogShapes.foreach { frogShape => frogShape.onMouseClicked = { (_: MouseEvent) => val frog = frogShape.frog if (model.canMoveOneRight(frog)) { view.jumpOneRight(frogShape) model.moveOneRight(frog) } else if (model.canMoveTwoRight(frog)) { view.jumpTwoRight(frogShape) model.moveTwoRight(frog) 34

ScalaFX Internals a.k.a. How to Write Your Own Scala DSLWith quotes from Stephen Colebourne (@jodastephen) to helpus keep our sanity!Disclaimer: Statements taken from http://blog.joda.org and may not accurately reflect his opinion or viewpoint. 35

Application Initialization> JavaFX Requires all UI code executed on the Application Thread> But our ScalaFX Application has no start method:object VanishingCircles extends JFXApp { stage = new Stage { … }} How Does This Code Work?!? 36

DelayedInit> Introduced in Scala 2.9> How to Use It:1. Extend a special trait called DelayedInit2. Implement a method of type:  def delayedInit(x: => Unit): Unit3. Store off the init closure and call it on the Application Thread Joda says… For me, Scala didnt throw enough away and added too much - a lethal combination. 37

Hierarchical Implicit Conversions> ScalaFX defines a set of proxies that mirror the JavaFX hierarchy> JavaFX classes are "implicitly" wrapped when you call a ScalaFX API> But Scala implicit priority ignores type hierarchy! JFXNode SFXNode JFXShape ? SFXShape JFXCircle ! SFXCircle 38

N-Level Implicit Precedence> Scala throws an exception if two implicits have the same precedence> Classes that are extended have 1 lower precedence:object HighPriorityIncludes extends LowerPriorityIncludes {…}trait LowerPriorityIncludes {…}> You can stack extended traits n-levels deep to reduce precision by n Joda says… Well, it may be type safe, but its also silent and very deadly. 39

Properties> JavaFX supports properties of type Boolean, Integer, Long, Float, Double, String, and Object> Properties use Generics for type safety> But generics dont support primitives…> JavaFX solves this with 20 interfaces and 44 classes for all the type/readable/writable combinations.> Can we do better? 40

@specialized> Special annotation that generates primitive variants of the class> Improves performance by avoiding boxing/unboxing trait ObservableValue[@specialized(Int, Long, Float, Double, Boolean) T, J]> Cuts down on code duplication (ScalaFX only has 18 property/value classes total) Joda says… Whatever the problem, the type system is bound to be part of the solution. 41

Bindings> How does Scala know what order to evaluate this in?text <== when (rect.hover || circle.hover&& !disabled) then textField.text + " isenabled" otherwise "disabled And why the funky bind operator?!? 42

Operator Precedence Rules> First Character Determines Precedence Lowest Precedence 10. (all letters) Exception Assignment 9. | Operators, which are 8. ^ even lower… 7. & 6. < > 11. Assignment Operators 5. = ! end with equal 4. : > But dont start with equal 3. + * > And cannot be one of:  <= 2. / %  >= 1. (all other special  != characters) Highest Precedence 43

Operator Precedencetext <== when (rect.hover || circle.hover 11 10 9&& !disabled) then textField.text + " is7 5 10 3enabled" otherwise "disabled" 10 Joda says… Personally, I find the goal of the open and flexible syntax (arbitrary DSLs) to be not worth the pain 44

Conclusion> You can use Scala and JavaFX together.> ScalaFX provides cleaner APIs that are tailor designed for Scala.> Try using ScalaFX today and help contribute APIs for our upcoming 1.0 release! http://code.google.com/p/scalafx/

Stephen Chin steveonjava@gmail.com tweet: @steveonjavaPro JavaFX 2 Platform Available Now! 46

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JavaFX and Scala - Like Milk and Cookies

by Stephen Chin

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