Java – disable items in JList

I'm using JList as part of the wizard to display all the steps to be performed (it also allows you to click one step to enter it) According to the previous steps, some steps will not necessarily be required These are the steps I disabled in the list that don't apply

How do i disable (block selection) some items in the list? Is there a better method than subclassing JList and covering each selection related method?

Solution

You must implement defaultlistselectionmodel, then you can set flag if isenabled

Simple example

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class JListDisabledItemDemo implements ItemListener,Runnable {

    private JFrame f = new JFrame("Colors");
    private static final String ITEMS[] = {" black "," blue "," green "," orange "," purple "," red "," white "," yellow "};
    private JList jList;
    private JCheck@R_32_2419@[] check@R_32_2419@es;
    private boolean[] enabledFlags;

    @Override
    public void run() {
        JPanel pnlEnablers = new JPanel(new GridLayout(0,1));
        pnlEnablers.setBorder(BorderFactory.createTitledBorder("Enabled Items"));
        check@R_32_2419@es = new JCheck@R_32_2419@[ITEMS.length];
        enabledFlags = new boolean[ITEMS.length];
        for (int i = 0; i < ITEMS.length; i++) {
            check@R_32_2419@es[i] = new JCheck@R_32_2419@(ITEMS[i]);
            check@R_32_2419@es[i].setSelected(true);
            check@R_32_2419@es[i].addItemListener(this);
            enabledFlags[i] = true;
            pnlEnablers.add(check@R_32_2419@es[i]);
        }
        jList = new JList(ITEMS);
        jList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        jList.setSelectionModel(new DisabledItemSelectionModel());
        jList.setCellRenderer(new DisabledItemListCellRenderer());
        jList.addListSelectionListener(new ListSelectionListener() {

            @Override
            public void valueChanged(ListSelectionEvent e) {
                if (!e.getValueIsAdjusting()) {
                    System.out.println("selection");
                }
            }
        });
        JScrollPane scroll = new JScrollPane(jList);
        scroll.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

        Container contentPane = f.getContentPane();
        contentPane.setLayout(new GridLayout(1,2));
        contentPane.add(pnlEnablers);
        contentPane.add(scroll);
        f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocation(240,280);
        UIManager.put("List.background",Color.lightGray);
        UIManager.put("List.selectionBackground",Color.orange);
        UIManager.put("List.selectionForeground",Color.blue);
        UIManager.put("Label.disabledForeground",Color.magenta);
        SwingUtilities.updateComponentTreeUI(f);
        f.pack();
        javax.swing.SwingUtilities.invokelater(new Runnable() {

            @Override
            public void run() {
                f.setVisible(true);
            }
        });
    }

    @Override
    public void itemStateChanged(ItemEvent event) {
        JCheck@R_32_2419@ check@R_32_2419@ = (JCheck@R_32_2419@) event.getSource();
        int index = -1;
        for (int i = 0; i < ITEMS.length; i++) {
            if (ITEMS[i].equals(check@R_32_2419@.getText())) {
                index = i;
                break;
            }
        }
        if (index != -1) {
            enabledFlags[index] = check@R_32_2419@.isSelected();
            jList.repaint();
        }
    }

    public static void main(String args[]) {
        SwingUtilities.invokelater(new JListDisabledItemDemo());
    }

    private class DisabledItemListCellRenderer extends DefaultListCellRenderer {

        private static final long serialVersionUID = 1L;

        @Override
        public Component getListCellRendererComponent(JList list,Object value,int index,boolean isSelected,boolean cellHasFocus) {
            Component comp = super.getListCellRendererComponent(list,value,index,false,false);
            JComponent jc = (JComponent) comp;
            if (enabledFlags[index]) {
                if (isSelected & cellHasFocus) {
                    comp.setForeground(Color.black);
                    comp.setBackground(Color.red);
                } else {
                    comp.setForeground(Color.blue);
                }
                if (!isSelected) {
                    if ((value.toString()).trim().equals("yellow")) {
                        comp.setForeground(Color.orange);
                        comp.setBackground(Color.magenta);
                    }
                }
                return comp;
            }
            comp.setEnabled(false);
            return comp;
        }
    }

    private class DisabledItemSelectionModel extends DefaultListSelectionModel {

        private static final long serialVersionUID = 1L;

        @Override
        public void setSelectionInterval(int index0,int index1) {
            if (enabledFlags[index0]) {
                super.setSelectionInterval(index0,index0);
            } else {
                /*
                 * The prevIoUsly selected index is before this one,* so walk forward to find the next selectable item.
                 */
                if (getAnchorSelectionIndex() < index0) {
                    for (int i = index0; i < enabledFlags.length; i++) {
                        if (enabledFlags[i]) {
                            super.setSelectionInterval(i,i);
                            return;
                        }
                    }
                } /*
                 * Otherwise,walk backward to find the next selectable item.
                 */ else {
                    for (int i = index0; i >= 0; i--) {
                        if (enabledFlags[i]) {
                            super.setSelectionInterval(i,i);
                            return;
                        }
                    }
                }
            }
        }
    }
}