Using JCheckBox as CellRenderer in JList

[Biliang Zhou]

Hi, I am trying to use JCheckBox as CellRenderer in JList. All go well, and the JCheckBoxes show up in the JList, but I cannot select or unselect these JCheckBoxes. They just don't respond to any mouse or keyboard action...

Here's the source code:

Thank you for looking into this issue!

################################################################

import java.awt.Component;

import javax.swing.JCheckBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.ListCellRenderer;

public class TestRenderer extends JPanel{

JList list;
Integer integerArray[] = new Integer[10];

public TestRenderer()
{
super();

list = new JList(integerArray);
ComboBoxRenderer renderer= new ComboBoxRenderer();
list.setCellRenderer(renderer);

this.add(list);
}

class ComboBoxRenderer extends JCheckBox implements ListCellRenderer {

public ComboBoxRenderer() {
setOpaque(true);
setHorizontalAlignment(LEADING);
setVerticalAlignment(CENTER);

for(int i = 0; i < 10; i ++)
{
integerArray[i] = new Integer(i);
}
}

public Component getListCellRendererComponent(
JList list,
Object value,
int index,
boolean isSelected,
boolean cellHasFocus) {
//Get the selected index. (The index param isn't
//always valid, so just use the value.)
int selectedIndex = ((Integer)value).intValue();

return new JCheckBox("Test: " + selectedIndex);
}
}

private static void createAndShowGUI() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new TestRenderer();
newContentPane.setOpaque(true);
frame.setContentPane(newContentPane);
frame.pack();
frame.setVisible(true);
}

public static void main(String[] args) {

javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});

}

}

################################################################

[Michael Dunn]

working example here

http://www.objects.com.au/java/examples/swing/CheckBoxList2.do

[edit]
looks like the link is now defunct

here's the code

    
// File:CheckListExample2.java
/* (swing1.1.1beta2) */
package examples;
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
 
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.ListCellRenderer;
import javax.swing.ListModel;
import javax.swing.ListSelectionModel;
import javax.swing.UIManager;
import javax.swing.border.EmptyBorder;
 

/**
 * @version 1.0 04/26/99
 */
class CheckListExample2 extends JFrame {
 
  public CheckListExample2() {
    super("CheckList Example");
    String[] strs = {"swing", "home", "basic", "metal", "JList"};
 
    final JList list = new JList( createData(strs) );
 
    list.setCellRenderer(new CheckListRenderer());
    list.setSelectionMode(ListSelectionModel.SINGLE_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);
        item.setSelected(! item.isSelected());
        Rectangle rect = list.getCellBounds(index, index);
        list.repaint(rect);
      }
    });
    JScrollPane sp = new JScrollPane(list);
 
    final JTextArea textArea = new JTextArea(3,10);
    JScrollPane textPanel = new JScrollPane(textArea);
    JButton printButton = new JButton("print");
    printButton.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()) {
            textArea.append(item.toString());
            textArea.append(System.getProperty("line.separator"));
          }
        }
      }
    });
    JButton clearButton = new JButton("clear");
    clearButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        textArea.setText("");
      }
    });
    JPanel panel = new JPanel(new GridLayout(2,1));
    panel.add(printButton);
    panel.add(clearButton);
 
    getContentPane().add(sp,    BorderLayout.CENTER);
    getContentPane().add(panel, BorderLayout.EAST);
    getContentPane().add(textPanel, 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 b) {
      isSelected = b;
    }
 
    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[]) {
    CheckListExample2 frame = new CheckListExample2();
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {System.exit(0);}
    });
    frame.setSize(300, 200);
    frame.setVisible(true);
  }
}

[ January 24, 2007: Message edited by: Michael Dunn ]

[Biliang Zhou]

I see the reason why:

The JList needs a MouseListener to handle the checking and unchecking of the checkboxes. That's what is missing in my code. I thought so long as JCheckBoxes are used as the ListCellRenderer they are ready to behave like JCheckBoxes standing alone, and that's not how ListCellRenderer works...

Thank you, Michael!