exercise14_1.java

Introduction to java programming 一书中所有编程练习部分的源码

// Exercise14_1.java: Use buttons to move message in a panel
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.*;

public class Exercise14_1 extends JApplet implements ActionListener {
  // Create a panel for displaying message
  protected MessagePanel messagePanel
    = new MessagePanel("Welcome to Java");

  // Declare two buttons to move the message left and right
  private JButton jbtLeft = new JButton("Left");
  private JButton jbtRight = new JButton("Right");

  /** Default constructor */
  public Exercise14_1() {
    // Set the background color of messagePanel
    messagePanel.setBackground(Color.yellow);

    // Create Panel jpButtons to hold two Buttons "<=" and "right =>"
    JPanel jpButtons = new JPanel();
    jpButtons.setLayout(new FlowLayout());
    jpButtons.add(jbtLeft);
    jpButtons.add(jbtRight);

    // Set keyboard mnemonics
    jbtLeft.setMnemonic('L');
    jbtRight.setMnemonic('R');

    // Set icons and remove text
//    jbtLeft.setIcon(new ImageIcon("image/left.gif"));
//    jbtRight.setIcon(new ImageIcon("image/right.gif"));
//    jbtLeft.setText(null);
//    jbtRight.setText(null);

    // Set tool tip text on the buttons
    jbtLeft.setToolTipText("Move message to left");
    jbtRight.setToolTipText("Move message to right");

    // Place panels in the frame
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(messagePanel, BorderLayout.CENTER);
    getContentPane().add(jpButtons, BorderLayout.SOUTH);

    // Register listeners with the buttons
    jbtLeft.addActionListener(this);
    jbtRight.addActionListener(this);
  }

  /** Handle ActionEvent */
  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == jbtLeft) {
      messagePanel.moveLeft();
    }
    else if (e.getSource() == jbtRight) {
      messagePanel.moveRight();
    }
  }
}