How to save GUI in XML file and vice versa??

[Michelle Wang]

Hello Sir:

I google a good example that meets my project requirements as code below,
I need to save it in XML format in disk with what I change/draw on the GUI, ie, I draw 10 lines(5 vertical and 5 horizontal) on it, then save it to MySaveLine.xml
then quit, later, I open project, it read this MySaveLine.xml from disk, and it automatically display all what I saved before ie:10 lines(5 vertical and 5 horizontal), it should be exactly same as what I did before.

But I have no idea how to do it,
Can Guru help here??

Thanks

    
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
import javax.swing.event.MouseInputAdapter;
 
public class LineDemo extends JPanel {
    List   lines = new ArrayList  ();
    Line2D.Double line = new Line2D.Double();
 
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(Color.blue);
        for(int j = 0; j < lines.size(); j++)
        g2.draw((Shape)lines.get(j));
        g2.setPaint(Color.green.darker());
        g2.draw(line);
    }
 
    public void setLine(Point start, Point end) {
        line.setLine(start, end);
        repaint();
    }
 
    public void addLine(Point start, Point end) {
        lines.add(new Line2D.Double(start, end));
        line.setLine(-1,-1,-1,-1);
        repaint();
    }
 
    public void resizeLine(int index, int pointIndex, int dx, int dy) {
        Line2D.Double line =  (Line2D.Double) lines.get(index);
        double x1 = line.getX1();
        double y1 = line.getY1();
        double x2 = line.getX2();
        double y2 = line.getY2();
        switch(pointIndex) {
            case 0:
                x1 += dx;
                y1 += dy;
                break;
            case 1:
                x2 += dx;
                y2 += dy;
        }
        line.setLine(x1, y1, x2, y2);
        repaint();
    }
 
    public void moveLine(int index, int dx, int dy) {
        Line2D.Double line = (Line2D.Double) lines.get(index);
        Point2D p1 = line.getP1();
        Point2D p2 = line.getP2();
        line.setLine(p1.getX()+dx, p1.getY()+dy, p2.getX()+dx, p2.getY()+dy);
        repaint();
    }
 
    public static void main(String[] args) {
        LineDemo demo = new LineDemo();
        LineManager manager = new LineManager(demo);
        demo.addMouseListener(manager);
        demo.addMouseMotionListener(manager);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(demo);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
class LineManager extends MouseInputAdapter {
    LineDemo component;
    final int S = 6;
    Rectangle net = new Rectangle(S,S);
    Point start;
    int selectedLineIndex = -1;
    int pointIndex;
    boolean resizing = false;
    boolean moving   = false;
    boolean dragging = false;
    Cursor cursor = Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR);
 
    LineManager(LineDemo demo) {
        component = demo;
    }
    
    public void mousePressed(MouseEvent e) {
        Point p = e.getPoint();
        if(selectedLineIndex != -1) {
            Line2D.Double line = (Line2D.Double)component.lines.get(selectedLineIndex);
            if(isResizing(line, p)) {
                pointIndex = line.getP1().distance(p) < S ? 0 : 1;
                resizing = true;
            } else {
                moving = true;
            }
        } else {
            dragging = true; 
        }
        start = p;
    }
 
    private boolean isResizing(Line2D.Double line, Point p) {
        Point2D p1 = line.getP1();
        Point2D p2 = line.getP2();
        return p1.distance(p) < S || p2.distance(p) < S;
    }
 
    public void mouseReleased(MouseEvent e) {
        if(dragging) {
            component.addLine(start, e.getPoint());
        }
        resizing = false;
        moving   = false;
        dragging = false;
    }
 
    public void mouseDragged(MouseEvent e) {
        Point end = e.getPoint();
        int x = end.x - start.x;
        int y = end.y - start.y;
        if(dragging) {
            component.setLine(start, end);
        } else {
            if(resizing) {
                component.resizeLine(selectedLineIndex, pointIndex, x, y);
            } else if(moving) {
                component.moveLine(selectedLineIndex, x, y);
            }
            start = end;
        }
    }
 
    public void mouseMoved(MouseEvent e) {
        Point p = e.getPoint();
        net.setLocation(p.x-S/2, p.y-S/2);
        boolean hovering = false;
        List   lines = component.lines;
        if(component == null || lines == null) return;
        for(int j = 0; j < lines.size(); j++) {
            if(((Shape)lines.get(j)).intersects(net)) {
                hovering = true;
                if(component.getCursor() == Cursor.getDefaultCursor()) {
                    selectedLineIndex = j;
                    component.setCursor(cursor);
                }
                break;
            }
        }
        if(!hovering && component.getCursor() == cursor) {
            selectedLineIndex = -1;
            component.setCursor(Cursor.getDefaultCursor());
        }
    }
}
 

[Rob Spoor]

Originally posted by Michelle Wang:
But I have no idea how to do it,
Can Guru help here??

I don't know, why don't you ask him?
(Sorry, couldn't hold back )


You only need to save and load the lines right? As in the contents of "List lines"?

If so it shouldn't be that hard.

Step 1: create your XML layout.
I'd go for the following:

<lines>
  <line>
    <start x="0" y="0">
    <end x="50", y="50">
  </line>
  <line>
    <start x="100" y="0"/>
    <end x="150", y="50"/>
  </line>
  ...
</lines>

Because that's what a line is: a start point and an end point, and each point has an X and Y coordinate.

Step 2: saving to XML. This is quite easy. Get a FileWriter, wrap it in a PrintWriter, and write everything:

printWriter.println("<lines>");
for (Iterator i = lines.iterator(); i.hasNext(); )
{
    Line2D line = (Line2D)i.next();
    printWriter.println("  <line>");
    printWriter.println("    <start x=\"" + line.getX1() + "\" y=\"" + line.getY1() + "\"/>");
    printWriter.println("    <end x=\"" + line.getX2() + "\" y=\"" + line.getY2() + "\"/>");
    printWriter.println("  </line>");
}
printWriter.println("</lines>");

Step 3: reading from XML. I'd use a library like JDOM. You let it parse the XML, and you read the elements. In pseudo code:

Element root = "get root element";
List lineElements = root.getChildren();
for (Iterator i = lineElements.iterator(); i.hasNext(); )
{
    Element lineElement = (Element)i.next();
    Element startElement = "get start element";
    double x1 = "get X value from start element";
    double y1 = "get Y value from start element";
    Element endElement = "get end element";
    double x2 = "get X value from end element";
    double y2 = "get Y value from end element";
    Line2D line = Line2D.Double(x1, y1, x2, y2);
    lines.add(line);
}

I'm sure you can fill in the blanks.


But if it were up to me, I'd serialize and deserialize the entire List of lines. It would be a lot easier, and you prevent someone opening your XML file with a text editor and messing it up.

[Darryl Burke]

Posting different code under different usernames doesn't make this any less of a cross post.
http://forums.sun.com/thread.jspa?threadID=5349871

7 minutes apart.

[Michelle Wang]

i think it is different issues by different persons.

[Gregg Bolinger]

Originally posted by Darryl Burke:
Posting different code under different usernames doesn't make this any less of a cross post.
http://forums.sun.com/thread.jspa?threadID=5349871

7 minutes apart.

It's interestingly close. Especially the usernames on both sites. Sunnymanman and Sunnygirl. Regardless, there is nothing wrong with posting the same questions on more than one site. We just don't like it in more than one forum. We just want you to be honest about it.

http://faq.javaranch.com/java/BeForthrightWhenCrossPostingToOtherSites

[Jelle Klap]

Originally posted by Rob Prime:

Because that's what a line is: a start point and an end point, and each point has an X and Y coordinate.

Not to be a smart-ass, but that's actually not what a line is
A line segment is bound by two end points, a line streches out to infinity (and beyond captain!)

[Darryl Burke]

Originally posted by Michelle Wang:
i think it is different issues by different persons.

Ha ha.

        f.setSize(400,400);
        f.setLocation(200,200);    

I rest my case.

[Rob Spoor]

Originally posted by Jelle Klap:


Not to be a smart-ass, but that's actually not what a line is
A line segment is bound by two end points, a line streches out to infinity (and beyond captain!)

A mathematical line yes; in Java it does have two points defining the line. Probably because "This Line2D represents a line segment in (x,y) coordinate space."

[Andre Uhres]

Hello Michelle Wang,
well done for showing a working example right away!
Here is one way to meet your project requirements using XMLEncoder:

1. Add these new instance variables before "List lines = new ArrayList ();":

private boolean initialized;
private String filename = "MySaveLine.xml";

2. Add these imports:

import java.beans.*;
import java.io.*;

3. Add these two methods:

    public void save() {
        if (initialized) {
            try {
                XMLEncoder o = new XMLEncoder(new BufferedOutputStream(new FileOutputStream(filename)));
                o.writeObject(lines);
                o.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
 
    public void load() {
        initialized = true;
        XMLDecoder d = null;
        try {
            d = new XMLDecoder(new BufferedInputStream(new FileInputStream(filename)));
            lines = (List) d.readObject();
            d.close();
        } catch (FileNotFoundException ex) {
        }
    }

4. Create this new class file:

import java.awt.Point;
import java.awt.geom.Line2D;
public class MyLine extends Line2D.Double{
    public MyLine() {
        super();
    }
    public MyLine(Point start, Point end) {
        super(start, end);
    }
    public void setX1(double x1) {
        this.x1 = x1;
    }
    public void setX2(double x2) {
        this.x2 = x2;
    }
    public void setY1(double y1) {
        this.y1 = y1;
    }
    public void setY2(double y2) {
        this.y2 = y2;
    }
}

5. Change all "Line2D.Double" to "MyLine" in your "LineDemo" file.

6. Add a call to "save();" in the "paintComponent" method.

7. Add this initializer after "List lines = new ArrayList ();":

    {
        load();
    }

[Michelle Wang]

wonderful!! Thanks

[Gregg Bolinger]

Well, looks like Andre answered it on both sites. Well done.

[Michelle Wang]

Yes, I think my one is more generic than that one. He is really super star