Question

I am using a JList, and I’m trying to use JTextAreas (that implement ListCellRenderer) for the cells. It isn’t working. The cells simply display the ListCellRenderer.toString() instead of the actual JTextArea. Could someone help? Thanks.

  DefaultListModel listModel = new DefaultListModel();
  JList list = new JList(listModel);
  add(list);

class ButtonListener implements ActionListener() {
  public void actionPerformed(ActionEvent e){
    listModel.clear();
    for (String s : stringArray) {
      listModel.addElement(new Listm(s));
    }
  }
}

class Listm extends JTextArea implements ListCellRenderer {
  protected Listm(String text) {
   setText(text); //Outputting the text element displays the desired String
  }

  public Component getListCellRendererComponent(JList list, Object object, int number, boolean bool, boolean bool2) {
    setPreferredSize(new Dimension(x, y));
    return this;
    }
  }
}

Answer 1

You should post compilable code only, and your code is a bit confusing. You shouldn’t pass text into the renderer’s constructor as this one constructor will be used for the single renderer that renders all items in the list (unless you want all to use the same code). You shouldn’t ignore the Object parameter that is passed into your getListCellRendererComponent method, for this is the data that the renderer item displays. For example:

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

public class MyGui extends JPanel {
   public static final String[] DATA = {"One\n1", "Two\n2", "Three\n3"};
   private DefaultListModel listModel = new DefaultListModel();
   private JList list = new JList(listModel);

   public MyGui() {
      list.setCellRenderer(new Listm(3, 30));
      add(new JScrollPane(list));
      for (String datum : DATA) {
         listModel.addElement(datum);
      }
   }

   private class Listm extends JTextArea implements ListCellRenderer {
      protected Listm(int rows, int cols) {
         super(rows, cols);
         setBorder(BorderFactory.createLineBorder(Color.blue));
      }

      public Component getListCellRendererComponent(JList list, Object value,
               int index, boolean isSelected, boolean cellHasFocus) {
         setText(value.toString());
         if (cellHasFocus) {
            setBackground(FOCUSED_COLOR);
         } else if (isSelected) {
            setBackground(SELECTED_COLOR);
         } else {
            setBackground(null);
         }
         return this;
      }
   }

   private static void createAndShowUI() {
      JFrame frame = new JFrame("MyGui");
      frame.getContentPane().add(new MyGui());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}