Question

I’m trying to serialize all of my objects when the user clicks on the File menu save command.
If I’m understanding correctly, the defaultReadObject() and defaultWriteObject() saves all of my objects except from static members so I tried to use these. My program is a kind of graph drawing program. It has a control frame where the user can set up the algorithm to run, and an other frame where the graph is painted.The the user can click on a next and previous button to see which nodes the algorithm is going through. So I’d like to save the actual state of the drawing so the user can continue the stepping after exit.
I’ve read that the defaultWriteObject should be called from the writeObject method but my problem is I don´t know how can I save the instance of the Control and Draw2 class from the actionlistener, which are created in the main function?
The relevant part of my code:

public class Control extends JPanel implements Serializable{

private String sourceFolder;
private String selectedAlg;
public List<Node> nodeList;
private JMenuBar jMenuBar;
private JMenu jMenu;
private JMenuItem jMenuItem;
private Draw2 draw;
private Search s;
//...
//and a lot more variables

void createControl(JFrame f, Draw2 d){
    jMenuBar = new JMenuBar();
    jMenu = new JMenu();
    jMenuItem = new JMenuItem();

    jMenu.setText("File");
    jMenuBar.add(jMenu);

    jMenuItem.setText("Save");
    jMenuItem.addActionListener(new SaveAction());

    jMenu.add(jMenuItem);

    //building the control window with textfields, buttons..

    draw=d;
    s=new Search();
}

private void writeObject( ObjectOutputStream out) throws IOException {

      out.defaultWriteObject();
}

//inner class, actionlistener for save menuItem
public class SaveAction implements ActionListener{
    public void actionPerformed(ActionEvent arg0) {

        try {
            FileOutputStream f = new FileOutputStream("savedfile");
            ObjectOutputStream out = new ObjectOutputStream(f);

            //So how can save the instance of control and draw class
 //here, which is created in the main function? 
//how to call writeObject and with what parameter?

        } catch (IOException o) {   
        }
    }
}

public static void main(String[] args){

    JFrame frame = new JFrame("Control");
    JFrame frame2 = new JFrame("Draw");

    Control cont = new control();
    Draw2 gp = new Draw2(cont);

    cont.createControl(frame, gp);

    frame.setJMenuBar(cont.jMenuBar);
    gp.setPreferredSize(new Dimension(0,0));
    //Control Frame
    frame.setSize(800,330);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(cont, BorderLayout.NORTH);
    frame.setVisible(true);
    //Drawing Frame
    frame2.setSize(800,600);
    frame2.setLocation(0, 330);
    frame2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);   
    frame2.add(gp);
    frame2.setVisible(true);        

}

}

public class Draw2 extends JPanel implements Serializable{

     public boolean toDraw = false;
     public boolean timedDraw = false;
     public boolean steppedDraw = false;
     private control c;

    public Draw2(control co){
        c=co;
    }
    public void paintComponent (Graphics g) {   
    //drawing the graph
    }
}

And one last question. When I load the object from the saved file how can I replace the running object to the loaded object? I thought about doing it through a paramater but actionPerformed cannot have a parameter besides ActionEvent.

 public class LoadAction implements ActionListener{

       Control contr;

      public LoadAction(Control control) {
           contr = control;
      }

    public void actionPerformed(ActionEvent arg0) {
        try {
            FileInputStream f = new FileInputStream("savedfile");
            ObjectInputStream in = new ObjectInputStream(f);
            contr= (Control)in.readObject();
           //so now I have the loaded object in the contr object, 
           //but How can copy it over the current object?
            in.close();

            System.out.println(contr.aktIndex);
        } catch (IOException o) {
            o.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

}

Answer 1

Extend action listener and pass the handle of the object to be saved to this action listener in the constructor.

You could move the object to be saved a class variable to do this.

public class SaveAction extends ActionListener {

  Control control;

  public SaveAction(Control control) {
    this.control = control;
  }

  public void actionPerformed(ActionEvent e) {
    // your save code here
  }

}

and then pass control when you new SaveAction in your code above…

new SaveAction(this);