JTabbedPane change listener to read from file

Question

I have a JTabbedPane containing 7 tabs each tab contains a class extending JPanel, what I need is if I change in any tab and save to a file, the changes made could be used in the other tabs without closing the program and running it again

I added the tabs to the JTabbedPane

tp.addTab("   Etudiant   ", new Etudiant());
            tp.addTab("   Enseignant   ", new Enseignant());
            tp.addTab("   Cours   ", new Cours());
            tp.addTab("   Groupes   ", new Groupe());
            tp.addTab("   Inscription   ", new Inscription());
            tp.addTab("   Horaires   ", new Horaires());
            tp.addTab("   Resultats   ", new Resultats());
            tp.addTab("   Divers   ", new Divers());

then I created a change listener to read from a file each time I choose a tab, I need to use the ArrayList read from the file in the class(of each tab)

tp.addChangeListener(new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                switch (tp.getSelectedIndex()) {
                    case 3:

                        if (file3.length() > 0) {
                            try {
                                ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Cours.out"));
                                listCours = (ArrayList) ois.readObject();

                                System.out.println("cours read");
                                System.out.println(listCours);
                            } catch (Exception ex) {
                                ex.printStackTrace();
                            }
                        } else {
                            listCours = new ArrayList();
                        }
                        if (file4.length() > 0) {
                            try {
                                ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Inscriptions.out"));
                                listIns = (ArrayList) ois.readObject();

                                System.out.println("insc read");
                            } catch (Exception ex) {
                                ex.printStackTrace();
                            }
                        } else {
                            listIns = new ArrayList();
                        }

                        break;

                    case 4:

                        if (file.length() > 0) {
                            try {
                                ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Etudiants.out"));
                                listEtud = (ArrayList) ois.readObject();

                                System.out.println("etud read");
                            } catch (Exception ex) {
                                ex.printStackTrace();
                            }
                        } else {
                            listEtud = new ArrayList();
                        }
                        if (file2.length() > 0) {
                            try {
                                ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Groupes.out"));
                                listGroupes = (ArrayList) ois.readObject();

                                System.out.println("group read");
                            } catch (Exception ex) {
                                ex.printStackTrace();
                            }
                        } else {
                            listGroupes = new ArrayList();
                        }
                        if (file3.length() > 0) {
                            try {
                                ObjectInputStream ois = new ObjectInputStream(new FileInputStream("Cours.out"));
                                listCours = (ArrayList) ois.readObject();

                                System.out.println("cours read");
                            } catch (Exception ex) {
                                ex.printStackTrace();
                            }
                        } else {
                            listCours = new ArrayList();
                        }
                        break;
                    case 5:
                        break;

                    case 6:

                        break;

                    default:
                        break;
                }
            }
        });

Okay, first off, I would define an interface to perform save and load operations, so you don’t need to do It in the ChangeListener, moving responsibility to the panels themselves. Next, you need to know which tab was previously selected, you can do this through the ChangeListener itself, so by the time you get to the end of the method, you would set the “previous” tab to the “current” tab — MadProgrammer, Jan 03 '19 at 20:45
@MadProgrammer can you please show me a simple exemple with code? — Joe Estephan, Jan 03 '19 at 20:56
https://stackoverflow.com/questions/29719292/jtabbedpane-track-previous-tab-selection — MadProgrammer, Jan 03 '19 at 20:57
@MadProgrammer i didn't understand why do i need the previous and the currents tabs — Joe Estephan, Jan 03 '19 at 21:13
How else were you intending to to save the data when the tab selection changes? — MadProgrammer, Jan 03 '19 at 21:22
@MadProgrammer i save the in an objectOutputStream to a file inside each tab — Joe Estephan, Jan 04 '19 at 04:50
my problem is that the data added in a tab could be used in other tabs without rerunning the program again — Joe Estephan, Jan 04 '19 at 04:51
sorry i meant that i cant use it in other tabs, i have to close the program and run it again to get them @MadProgrammer — Joe Estephan, Jan 04 '19 at 05:02
0096176607778 this is my whatsapp number if it doesn't bother you i really appreciate your help — Joe Estephan, Jan 04 '19 at 05:07
Well, I go back to my first comment, it's not the responsibility of the `ChangeListener` to load this data, it's the responsibility of the individual tabs. I would, gain, define a simple `interface` which provides a `load` method, which can be used by the `ChangeListener` to notify the tabs (that conform to the interface) that they should load the required data — MadProgrammer, Jan 04 '19 at 05:14
@MadProgrammer do i still need the previous and the current? — Joe Estephan, Jan 04 '19 at 05:18
I know i am being rude but can u please show me a simple exemple? — Joe Estephan, Jan 04 '19 at 05:22

score 1 · Accepted Answer · answered Jan 04 '19 at 05:37

It's not the responsibility of the ChangeListener to be making decisions about what should be done when a tab is selected. Instead, you need some way to instruct the selected tab that it should perform what ever operations it needs to when selected. This decouples the code and allows you to change the order of the tabs without affect the remaining code.

Start by defining a simple concept of something which is loadable...

public interface Loadable {
    public void load();
}

Then each tab/panel you want to be notified when the tab selection changes should implement this interface

public class LoadableTabPane extends JPanel implements Loadabel {
    //...
    public void load() {
        // Performing the loading here
    }
}

Then when the tab selection changes, you inspect the selected component to determine of it's an instanceof Loadable and if it is, you cast it and call its load method...

tp.addChangeListener(new ChangeListener() {
    @Override
    public void stateChanged(ChangeEvent e) {
        Component selectedComponent = tp.getSelectedComponent();
        if (selectedComponent instanceof Loadable) {
            ((Loadable)selectedComponent).load();
        }
    }
}

JTabbedPane change listener to read from file

1 Answers1