使用按钮

## 题目要求 ##
在面板上显示一条消息，然后使用两个按钮=》和《=在面板上向右或者向左移动这个消息。

ButtonDemo.java

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

public class ButtonDemo extends JFrame {

protected MessagePanel messagePanel = new MessagePanel("Welocme to my home");

private JButton jbtLeft=new JButton("<=");
private JButton jbtRight= new JButton("=>");

public static void main(String[] args)
{
ButtonDemo frame= new ButtonDemo();
frame.setTitle("ButtonDemo");
frame.setSize(250,100);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public ButtonDemo()
{
messagePanel.setBackground(Color.white);
JPanel jpButtons=new JPanel();

jpButtons.add(jbtLeft);
jpButtons.add(jbtRight);

jbtLeft.setMnemonic('L');
jbtRight.setMnemonic('R');

jbtLeft.setToolTipText("move message to left");
jbtRight.setToolTipText(" move message to right");

setLayout(new BorderLayout());
add(messagePanel,BorderLayout.CENTER);
add(jpButtons,BorderLayout.SOUTH);

jbtLeft.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
messagePanel.moveLeft();

}});
jbtRight.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
messagePanel.moveRight();
}
});
}
}

## 子类MessagePanel.java ##

“`

import java.awt.*;

import java.awt.event.ActionListener;

import java.awt.event.ActionEvent;

import javax.swing.*;

public class ButtonDemo extends JFrame {

protected MessagePanel messagePanel = new MessagePanel("Welocme to my home");

private JButton jbtLeft=new JButton("<=");
private JButton jbtRight= new JButton("=>");

public static void main(String[] args)
{
ButtonDemo frame= new ButtonDemo();
frame.setTitle("ButtonDemo");
frame.setSize(250,100);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public ButtonDemo()
{
messagePanel.setBackground(Color.white);
JPanel jpButtons=new JPanel();

jpButtons.add(jbtLeft);
jpButtons.add(jbtRight);

jbtLeft.setMnemonic('L');
jbtRight.setMnemonic('R');

jbtLeft.setToolTipText("move message to left");
jbtRight.setToolTipText(" move message to right");

setLayout(new BorderLayout());
add(messagePanel,BorderLayout.CENTER);
add(jpButtons,BorderLayout.SOUTH);

jbtLeft.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
messagePanel.moveLeft();

}});
jbtRight.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
messagePanel.moveRight();
}
});
}

}

`