在 JavaFX 应用程序中将颜色保存为状态

Question

I have an application that draws shapes. Shapes know their color and size (an integer). I would like for this program to save shapes into a file. JavaFX's color class is not serializable.

Should I not be serializing objects and should I forget about using ObjectOutputStreams and ObjectInputStreams? Is there another preferred way to do this in JavaFX?

Answer 1

Here is a quick arabesque around the problem.

import java.io.Serializable;
import javafx.scene.paint.Color;
public class SerializableColor implements Serializable
{
    private double red;
    private double green;
    private double blue;
    private double alpha;
    public SerializableColor(Color color)
    {
        this.red = color.getRed();
        this.green = color.getGreen();
        this.blue = color.getBlue();
        this.alpha = color.getOpacity();
    }
    public SerializableColor(double red, double green, double blue, double alpha)
    {
        this.red = red;
        this.green = green;
        this.blue = blue;
        this.alpha = alpha;
    }
    public Color getFXColor()
    {
        return new Color(red, green, blue, alpha);
    }
}

Answer 2

I can´t tell you, which is the most common way to solve your usecase, but we have a simular one, where we serialize a shapes state. We use xStream to persist its state in XML.

For Color Attributes we created an own ColorConverter to make Color Serializable. The converter just cares about the red, green and blue value of a color as well as its opacity. This way, the XML stays simple and clean, when it comes to color attributes.

Talking about serialization of shapes, the whole thing gets more complicated, since xStream serializes all dependencies of an object. Therefore you might want to create template objects for each shade to just store the information you need and ignore the rest. This will also insure, that you stay independent of possible future shape changes within the javafx api.

There is also a small javafx xstream converter collection called XStreamFX , which might holds interesting converters for you.

Answer 3

You can store a serializeable class instance to a file instead of your shapes. Let this class implement a method Object readResolve() throws ObjectStreamException that restores the shape.

Here's a simple example for Rectangle , that serializes the width, height and color:

public class RectData implements Serializable {

    public RectData(Rectangle rect) {
        this.width = rect.getWidth();
        this.height = rect.getHeight();
        Color color = (Color) rect.getFill();
        this.color = (int) (color.getRed() * 0xFF) | 
                ((int) (color.getGreen() * 0xFF)) << 010 | 
                ((int) (color.getBlue() * 0xFF)) << 020 | 
                ((int) (color.getOpacity() * 0xFF)) << 030;
    }

    private final int color;
    private final double width;
    private final double height;

    private Object readResolve() throws ObjectStreamException {
        Rectangle rect = new Rectangle(width, height);
        rect.setFill(Color.rgb(
                color & 0xFF,
                (color >>> 010) & 0xFF,
                (color >>> 020) & 0xFF,
                (color >>> 030) / 255d));
        return rect;
    }

}

Example serialisation

try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("data/shapeser.ser"))) {
    Rectangle rect = new Rectangle(100, 200);
    rect.setFill(Color.CHOCOLATE);
    oos.writeObject(new RectData(rect));
}

Deserialisation

Node node;
try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream("data/shapeser.ser"))) {
    node = (Node) ois.readObject();
}