One thing that I like a lot to do with JavaFX is draggable objects. Due to some recent changes in the JavaFX syntax my old codes for that are no longer working. Joshua Marinacci from Sun’s JavaFX engineering team and other guys from the JavaFX community gave me some tips. Here some strategies I’m using for making draggable nodes in JavaFX.

In this first example, a simple draggable ellipse.


video url: http://www.youtube.com/watch?v=pAJHH-mPLaQ

import javafx.application.*;
import javafx.scene.paint.*;
import javafx.scene.geometry.*;
import javafx.input.*;
 
Frame {
    width: 300, height: 300, visible: true
    stage: Stage {
        content: [
            Ellipse {
                var endX = 0.0; var endY = 0.0
                var startX = 0.0; var startY = 0.0
                centerX: 150, centerY: 150
                radiusX: 80, radiusY: 40
                fill: Color.ORANGE
                translateX: bind endX
                translateY: bind endY
                onMousePressed: function(e:MouseEvent):Void {
                    startX = e.getDragX()-endX;
                    startY = e.getDragY()-endY;
                }
                onMouseDragged: function(e:MouseEvent):Void {
                    endX = e.getDragX()-startX;
                    endY = e.getDragY()-startY;
                }
            }
        ]
 
    }
}

When you need to create a group of draggable objects, you can try thie approach of a draggable group like this. Inside on it, you can put whatever you want.


Video url: http://www.youtube.com/watch?v=mHOcPRrgQCQ

import javafx.application.*;
import javafx.scene.paint.*;
import javafx.scene.geometry.*;
import javafx.input.*;
import javafx.scene.*;
import javafx.scene.effect.*;
import javafx.scene.image.*;
import javafx.animation.*;
 
// a graggable group
public class DragGroup extends CustomNode{
    public attribute content: Node[];
 
    private attribute endX = 0.0;
    private attribute endY = 0.0;
 
    private attribute startX = 0.0;
    private attribute startY = 0.0;
 
    public function create(): Node {
        return Group{
            translateX: bind endX
            translateY: bind endY
            content: bind content
        }
    }
 
    override attribute onMousePressed = function(e:MouseEvent):Void {
        startX = e.getDragX()-endX;
        startY = e.getDragY()-endY;
    }
 
    override attribute onMouseDragged = function(e:MouseEvent):Void {
        endX = e.getDragX()-startX;
        endY = e.getDragY()-startY;
    }
}
 
// angle animation, cycles between 0 to 360 in 36 seconds
var angle = 0.0;
var angleAnimation = Timeline {
    repeatCount: Timeline.INDEFINITE
    keyFrames : [
        KeyFrame {
            time: 0s
            values: 
                    angle => 0.0
        },
        KeyFrame{
            time: 36s
            values :  
                    angle => 360.0 tween Interpolator.LINEAR
        }
    ]
}
 
// some pictures from my Flickr albums 
var me    = "http://farm4.static.flickr.com/3042/2746737338_aa3041f283_m.jpg";
 
 
 
var dog   = "http://farm4.static.flickr.com/3184/2717290793_ec14c26a85_m.jpg";
var plant = "http://farm4.static.flickr.com/3014/2731177705_bed6d6b8fa_m.jpg";
var bird  = "http://farm4.static.flickr.com/3190/2734919599_a0110e7ce0_m.jpg";
var me_89  = "http://farm3.static.flickr.com/2138/2308085138_7b296cc5d0_m.jpg";
 
 
Frame {    
    width: 640, height: 480, visible: true
    stage: Stage {
        fill: Color.BLACK
        content: [
            DragGroup{
                content: ImageView {
                    anchorX: 120, anchorY: 90
                    rotate: bind 30 + angle
                    image: Image { backgroundLoading: true, url: me }
                }
            },
            DragGroup {
                translateX: 300, translateY: 50
                content: ImageView {
                    anchorX: 120, anchorY: 90
                    rotate: bind -30 + angle
                    image: Image { backgroundLoading: true, url: dog }
                }
            },
            DragGroup {
                translateX: 300, translateY: 300
                content: ImageView {
                    anchorX: 120, anchorY: 90
                    rotate: bind 90 + angle
                    image: Image { backgroundLoading: true, url: plant }
                }                
            },
            DragGroup {
                translateX: 200
                translateY: 200
                content: ImageView {
                    anchorX: 120, anchorY: 90
                    rotate: bind 90 + angle
                    image: Image { backgroundLoading: true, url: bird }
                }                
            },
            DragGroup {
                translateX: 30
                translateY: 200
                content: ImageView {
                    anchorX: 85, anchorY: 120
                    rotate: bind angle + 180
                    image: Image { backgroundLoading: true, url: me_89 }
                }                
            },
        ]
 
    }
 
    closeAction: function() { 
        java.lang.System.exit( 0 ); 
    }
}
 
angleAnimation.start();

One more example, using the same class DragGroup, we can put multiple nodes using lists.


Video url: http://www.youtube.com/watch?v=gJqy7EdtEqs

import javafx.application.*;
import javafx.scene.*;
import javafx.scene.geometry.*;
import javafx.scene.paint.*;
import javafx.input.*;
import javafx.animation.*;
import java.lang.Math;
 
// Class to create a draggable group of objects
public class DragGroup extends CustomNode{
    public attribute content: Node[];
 
    private attribute endX = 0.0;
    private attribute endY = 0.0;
 
    private attribute startX = 0.0;
    private attribute startY = 0.0;
 
    override attribute onMousePressed = function(e:MouseEvent):Void {
        startX = e.getDragX()-endX;
        startY = e.getDragY()-endY;
    }
 
    override attribute onMouseDragged = function(e:MouseEvent):Void {
        endX = e.getDragX()-startX;
        endY = e.getDragY()-startY;
    }
 
    public function create(): Node {
        return Group{
            translateX: bind endX
            translateY: bind endY
            content: bind content
        }
    }
}
 
// angle animation, cycles between 0 to 360 in 10 seconds
var angle = 0.0;
var angleAnimation = Timeline {
    repeatCount: Timeline.INDEFINITE
    keyFrames : [
        KeyFrame {
            time: 0s
            values: angle => 0.0
        },
        KeyFrame{
            time: 10s
            values :  angle => 360.0 tween Interpolator.LINEAR
        }
    ]
}
 
// breath animation, go and back from 0.0 to 10.0 in 2 seconds
var breath = 0.0;
var breathAnimation = Timeline {
    repeatCount: Timeline.INDEFINITE
    autoReverse: true
    keyFrames : [
        KeyFrame {
            time: 0s
            values: breath => 0.0
        },
        KeyFrame{
            time: 1s
            values :  breath => 10.0 tween Interpolator.LINEAR
        }
    ]
}
 
// Creates n multi colored floating circles around a bigger circle
var n = 12;
var colors = [
    Color.BLUE, Color.AQUA, Color.MAGENTA, Color.RED,
    Color.YELLOW, Color.ORANGE, Color.HOTPINK, Color.LIME
];
var chosen = Color.YELLOW;
var floatingCircles = Group{
    rotate: bind angle
    content: for (i in [1..n]) 
    Circle {
        fill: colors[i mod sizeof colors]
        radius: 10
        centerX: Math.cos(i * 2 * Math.PI/n) * 70
        centerY: Math.sin(i * 2 * Math.PI/n) * 70
        onMouseClicked: function( e: MouseEvent ):Void {
            chosen = colors[i mod sizeof colors];
        }
    }
}
var circle = Circle{
    radius: bind 50 + breath
    fill: bind chosen
}
 
 
Frame {
    width: 400, height: 400, visible: true
    stage: Stage {
        fill: Color.BLACK
        content: [
            DragGroup{
                translateX: 200, translateY: 200
                content: [circle, floatingCircles]
            }
        ]
    }
 
    closeAction: function() { 
        java.lang.System.exit( 0 ); 
    }
}
 
// starts all animations
angleAnimation.start();
breathAnimation.start();