list.java

Thinking in JAVA第四版源代码

//: gui/List.java
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import static net.mindview.util.SwingConsole.*;

public class List extends JFrame {
  private String[] flavors = {
    "Chocolate", "Strawberry", "Vanilla Fudge Swirl",
    "Mint Chip", "Mocha Almond Fudge", "Rum Raisin",
    "Praline Cream", "Mud Pie"
  };
  private DefaultListModel lItems = new DefaultListModel();
  private JList lst = new JList(lItems);
  private JTextArea t =
    new JTextArea(flavors.length, 20);
  private JButton b = new JButton("Add Item");
  private ActionListener bl = new ActionListener() {
    public void actionPerformed(ActionEvent e) {
      if(count < flavors.length) {
        lItems.add(0, flavors[count++]);
      } else {
        // Disable, since there are no more
        // flavors left to be added to the List
        b.setEnabled(false);
      }
    }
  };
  private ListSelectionListener ll =
    new ListSelectionListener() {
      public void valueChanged(ListSelectionEvent e) {
        if(e.getValueIsAdjusting()) return;
        t.setText("");
        for(Object item : lst.getSelectedValues())
          t.append(item + "\n");
      }
    };
  private int count = 0;
  public List() {
    t.setEditable(false);
    setLayout(new FlowLayout());
    // Create Borders for components:
    Border brd = BorderFactory.createMatteBorder(
      1, 1, 2, 2, Color.BLACK);
    lst.setBorder(brd);
    t.setBorder(brd);
    // Add the first four items to the List
    for(int i = 0; i < 4; i++)
      lItems.addElement(flavors[count++]);
    add(t);
    add(lst);
    add(b);
    // Register event listeners
    lst.addListSelectionListener(ll);
    b.addActionListener(bl);
  }
  public static void main(String[] args) {
    run(new List(), 250, 375);
  }
} ///:~