JList need twice click to update a CheckableItem

Question

I have this small snippet of code that display a simple panel with a list of checkboxes. The behavior must be the following:

• if the checkbox "[] all" is selected every other checKbox must be unchecked, otherwise (when the "[] all" checkbox isn't selected) the user can select any number of checkboxes.

• if a checkbox different from "[] all" is checked then the "[] all" checkbox must be unchecked

Far from now nothing strange except that if the checkbox "[] all" is selected then the user must press twice each other checkbox in order to mark it as selected. The first click uncheck the "[] all" checkbox but does not check the selected checkbox. I would like to get both behaviors together. I guess miss something (a sync event maybe...)

Here the code (is self contained so if you want you can run it as it is):

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

public class CheckListPlot extends JFrame {

public CheckListPlot() {
    super("CheckList");
    String[] strs = { "a", "b", "c", "d", "e", "f", "g", "h", "i" };

    JLabel label = new JLabel("Please, before to start the simulation, choose what species you desire to plot");
    Font font = new Font("Tahoma", label.getFont().getStyle(), label.getFont().getSize() - 2);
    label.setFont(font);

    JPanel allCheckpanel = new JPanel(new BorderLayout());
    allCheckpanel.setBorder(new EmptyBorder(6, 6, 6, 6));
    final JCheckBox allCheck = new JCheckBox("all", false);
    allCheckpanel.add(allCheck, BorderLayout.WEST);

    JPanel labelPanel = new JPanel(new GridLayout(1, 1));
    labelPanel.setBorder(new EmptyBorder(10, 10, 10, 10));
    labelPanel.add(label);

    final JList list = new JList(createData(strs));

    list.setCellRenderer(new CheckListRenderer());
    list.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
    list.setBorder(new EmptyBorder(0, 4, 0, 0));

    list.addMouseListener(new MouseAdapter() {
        public void mouseClicked(MouseEvent e) {
            int index = list.locationToIndex(e.getPoint());
            CheckableItem item = (CheckableItem) list.getModel().getElementAt(index);
            System.out.println("item " + item.toString() + " is selected before? " + item.isSelected());
            item.setSelected(!item.isSelected());
            System.out.println("item " + item.toString() + " is selected after ? " + item.isSelected());
            Rectangle rect = list.getCellBounds(index, index);
            list.repaint(rect);
            if(allCheck.isSelected()){
                allCheck.setSelected(false);

            }


        }
    });


    JScrollPane sp = new JScrollPane(list);

    JButton simulateButton = new JButton("simulate");
    simulateButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            ListModel model = list.getModel();
            int n = model.getSize();
            for (int i = 0; i < n; i++) {
                CheckableItem item = (CheckableItem) model.getElementAt(i);
                if (item.isSelected()) {
                    System.out.println(item.toString());


                }
            }
        }
    });

    JPanel panel = new JPanel(new GridLayout(1, 1));
    panel.add(simulateButton);

    allCheck.addItemListener(new ItemListener() {
        public void itemStateChanged(ItemEvent e) {
            for(int i =0 ; i< list.getModel().getSize(); i++){
                ((CheckableItem)list.getModel().getElementAt(i)).setSelected(false);
                Rectangle rect = list.getCellBounds(i, i);
                list.repaint(rect);
            }               


        }
    });

    getContentPane().add(labelPanel, BorderLayout.NORTH);

    getContentPane().add(allCheckpanel, BorderLayout.NORTH);
    getContentPane().add(sp, BorderLayout.CENTER);
    getContentPane().add(panel, BorderLayout.SOUTH);
}

private CheckableItem[] createData(String[] strs) {
    int n = strs.length;
    CheckableItem[] items = new CheckableItem[n];
    for (int i = 0; i < n; i++) {
        items[i] = new CheckableItem(strs[i]);
    }
    return items;
}

class CheckableItem {
    private String str;

    private boolean isSelected;

    public CheckableItem(String str) {
        this.str = str;
        isSelected = false;
    }

    public void setSelected(boolean value) {
        isSelected = value;
    }

    public boolean isSelected() {
        return isSelected;
    }

    public String toString() {
        return str;
    }
}

class CheckListRenderer extends JCheckBox implements ListCellRenderer {

    public CheckListRenderer() {
        setBackground(UIManager.getColor("List.textBackground"));
        setForeground(UIManager.getColor("List.textForeground"));
    }

    public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean hasFocus) {
        setEnabled(list.isEnabled());
        setSelected(((CheckableItem) value).isSelected());
        setFont(list.getFont());
        setText(value.toString());
        return this;
    }
}

public static void main(String args[]) {
    try {
        UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
    } catch (Exception evt) {}

    CheckListPlot frame = new CheckListPlot();
    frame.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    });
    frame.setSize(300, 200);
    frame.setVisible(true);
}
}

Answer 1

update your method of adding ItemListener on all check box as follows

allCheck.addItemListener(new ItemListener() {
    public void itemStateChanged(ItemEvent e) {
        for(int i =0 ; i< list.getModel().getSize(); i++){
            if(e.getStateChange() == ItemEvent.SELECTED)
            {
            System.out.println("value"+e.getStateChange()); 
            ((CheckableItem)list.getModel().getElementAt(i)).setSelected(true);
            } else
            {
                ((CheckableItem)list.getModel().getElementAt(i)).setSelected(false);
            }
            Rectangle rect = list.getCellBounds(i, i);
            list.repaint(rect);
        }
    }
});

Answer 2

Ok I solved but I don't know why... I'm writing here the solution in the hope that someone can explain me this strange behavior. I would be very happy to understand why this little change solve everything.

basically it is sufficent to change this small fragment of code:

list.addMouseListener(new MouseAdapter() {
        public void mouseClicked(MouseEvent e) {
                    // I have made the operation on the JCheckBox first of all
            if(allCheck.isSelected()){
                allCheck.setSelected(false);
            }


            int index = list.locationToIndex(e.getPoint());
            CheckableItem item = (CheckableItem)     list.getModel().getElementAt(index);
            System.out.println("item " + item.toString() + " is selected before? " + item.isSelected());
            item.setSelected(!item.isSelected());   
            System.out.println("item " + item.toString() + " is selected after ? " + item.isSelected());
            Rectangle rect = list.getCellBounds(index, index);
            list.repaint(rect);




        }
    });

I think that is due to some synchronization issue between JCheckBox class and JList class, don't you? It seems that the operation on JCheckBox (in the previous code), in some ways, cause JList to lost the focus, so the second click resets the JList focus