JavaFX, handling events with overlapping elements

Silveira — Mon, 28 Jul 2008 03:21:46 +0000

Here is a problem I faced those days while programming with JavaFX.
When you perform a click in a JavaFX area, mouse events are called to all nodes through that position. You can see this behavior in this video.

Example 1.

Here is the code.

import javafx.application.*;
import javafx.scene.geometry.*;
import javafx.scene.geometry.Rectangle;
import javafx.scene.paint.Color;
import javafx.input.MouseEvent;
 
Frame {
    width: 200
    height: 200
    visible: true
    stage: Stage {
        content: [
            Rectangle {
                var color1 = Color.BLUE;
                x: 10, y: 10, width: 140, height: 90, fill: bind color1
                onMouseClicked: function( e: MouseEvent ):Void {
                    if (color1==Color.BLUE){
                        color1 = Color.GREEN;
                    } else {
                        color1 = Color.BLUE
                    }
                }
            },
            Circle {
                var color2 = Color.RED
                centerX: 100, centerY: 100, radius: 40, fill: bind color2
                onMouseClicked: function( e: MouseEvent ):Void {
                    if (color2==Color.YELLOW){
                        color2 = Color.RED;
                    } else {
                        color2 = Color.YELLOW
                    }
                }
            }
        ]
    }
}

This is the default behavior. All node are called with a mouse event. Is a expected and robust behavior but sometimes we just don’t want that. We want events called to just one node or a set of nodes.

Example 2.

Is exactly the same code but with blocksMouse: true in the circle node. When blocksMouse is true the mouse event will not be called to others node behind it.

package overlapping;
 
import javafx.application.*;
import javafx.scene.geometry.*;
import javafx.scene.geometry.Rectangle;
import javafx.scene.paint.Color;
import javafx.input.MouseEvent;
 
Frame {
    width: 200
    height: 200
    visible: true
    stage: Stage {
        content: [
            Rectangle {
                var color1 = Color.BLUE;
                x: 10, y: 10, width: 140, height: 90, fill: bind color1
                onMouseClicked: function( e: MouseEvent ):Void {
                    if (color1==Color.BLUE){
                        color1 = Color.GREEN;
                    } else {
                        color1 = Color.BLUE
                    }
                }
            },
            Circle {
                var color2 = Color.RED
                centerX: 100, centerY: 100, radius: 40, fill: bind color2
                blocksMouse: true
                onMouseClicked: function( e: MouseEvent ):Void {
                    if (color2==Color.YELLOW){
                        color2 = Color.RED;
                    } else {
                        color2 = Color.YELLOW
                    }
                }
            }
        ]
    }
}

Thanks guys on the OpenJDK user mail list and at OpenJFX Forum, specially this thread.

Silveira Neto » Videos

JavaFX, handling events with overlapping elements