/*
   AnimationDemoFX.java Copyright (c) Kari Laitinen

   http://www.naturalprogramming.com/

   2014-12-15 File created.
   2014-12-29 Last modification.

   This program shows a blinking ball on the screen.

   The following things are demonstrated:
      - the use of classes Timeline and KeyFrame to control animation
      - using a Lambda experssion to write an EventHandler

*/


import javafx.animation.* ;
import javafx.util.Duration;
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.scene.shape.*;
import javafx.stage.Stage;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;


public class AnimationDemoFX extends Application
{
   public void start( Stage stage )
   {
      Group group_for_ball = new Group() ;

      stage.setTitle( "AnimationDemoFX.java" ) ;

      Scene scene = new Scene( group_for_ball, 600, 500 ) ;

      scene.setFill( Color.LIGHTYELLOW ) ;

      Circle blinking_ball = new Circle( 300, 250, 64, Color.CYAN ) ;

      group_for_ball.getChildren().add( blinking_ball ) ;
           
      stage.setScene( scene ) ;
      stage.show() ;

      Timeline timeline = new Timeline() ;

      timeline.setCycleCount( Animation.INDEFINITE ) ;

      // The following EventHandler specifies what will be done
      // after the animation specified by the KeyFrame is finished.
      // The arrow token -> identifies a Lambda expression.

      EventHandler<ActionEvent> on_finished = ( ActionEvent event ) ->
      {
         if ( blinking_ball.getFill() == Color.CYAN )
         {
            blinking_ball.setFill( Color.TRANSPARENT ) ;
         }
         else
         {
            blinking_ball.setFill( Color.CYAN ) ;
         }

         System.out.print( "\n on_finished executed. " ) ;
      } ;

      // Next we specify a KeyFrame whose execution takes 1 second.
      // The EventHandler will be executed after that.
      // No actual modification of values is specified by this KeyFrame.
      // This can thus be considered a misuse of a KeyFrame.

      KeyFrame keyframe = new KeyFrame( Duration.millis( 1000 ),
                                        on_finished ) ;

      timeline.getKeyFrames().add( keyframe ) ;

      timeline.play() ;
   }

   public static void main( String[] command_line_parameters )
   {
      launch( command_line_parameters ) ;
   }
}


/*  NOTES:


      // Here is an alternative way to specify an EventHandler:

      EventHandler<ActionEvent> on_finished = new EventHandler<ActionEvent>()
      {
         public void handle(ActionEvent t)
         {
            if ( blinking_ball.getFill() == Color.CYAN )
            {
               blinking_ball.setFill( Color.TRANSPARENT ) ;
            }
            else
            {
               blinking_ball.setFill( Color.CYAN ) ;
            }

            System.out.print( " jee " ) ;
         }
      };


The following were useful pages when I developed this program:

https://docs.oracle.com/javase/8/javafx/api/javafx/animation/Timeline.html

http://docs.oracle.com/javase/8/javafx/visual-effects-tutorial/basics.htm#BEIIDFJC

https://docs.oracle.com/javase/8/javafx/api/javafx/scene/shape/Circle.html

http://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html



    A NOTE RELATED TO HUMAN PHYSIOLOGY:

    This program can be used to demonstrate the strange 
    behaviour of our sight system. If you watch the blinking ball
    from a short distance, you'll notice that when the ball disappears
    from the screen you see a kind of shadow of the ball. The color
    of the shadowish ball seems to be close to magenta, which is a
    kind of opposite color to cyan, the color of the 'real' ball.
    The reason for seeing this kind of shadow of the ball is in
    our eyes. Our sight system is such that the sight cells inside
    our eyes remember the object (i.e. the ball) that disappears,
    but they produce the opposite color for the disappeared object.
    (This nice feature in this program was discovered by professor
    Matti Weckström from the University of Oulu.)

*/