import java.awt.*;
import java.awt.event.*;

public class MultiListener extends Frame implements ActionListener {

    TextArea topTextArea;
    TextArea bottomTextArea;
    Button button1, button2;

    public MultiListener(String s) {       
        super( s); 
        
        Label l = null;
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints c = new GridBagConstraints();
        setLayout(gridbag);   	//Frame設置為GridBagLayout布局管理器。

        c.fill = GridBagConstraints.BOTH;
        c.gridwidth = GridBagConstraints.REMAINDER;
        l = new Label("監聽器聽到的:");
        gridbag.setConstraints(l, c);
        add(l);

        c.weighty = 1.0;
        topTextArea = new TextArea(5, 20);
        topTextArea.setEditable(false);
        gridbag.setConstraints(topTextArea, c);
        add(topTextArea);

        c.weightx = 0.0;
        c.weighty = 0.0;
        l = new Label("偷聽者聽到的:");
        gridbag.setConstraints(l, c);
        add(l);

        c.weighty = 1.0;
        bottomTextArea = new TextArea(5, 20);
        bottomTextArea.setEditable(false);
        gridbag.setConstraints(bottomTextArea, c);
        add(bottomTextArea);

        c.weightx = 1.0;
        c.weighty = 0.0;
        c.gridwidth = 1;
        c.insets = new Insets(10, 10, 0, 10);
        button1 = new Button("啦 啦 啦");
        gridbag.setConstraints(button1, c);
        add(button1);

        c.gridwidth = GridBagConstraints.REMAINDER;
        button2 = new Button("你別說話!");
        gridbag.setConstraints(button2, c);
        add(button2);

        //當前MultiListener對象同時監聽兩個Button的事件。
        button1.addActionListener(this);
        button2.addActionListener(this);

        //為第二個Button再注冊一個監聽器。
        button2.addActionListener(new Eavesdropper());
        
        //向窗口注冊響應關閉窗口操作的監聽器。
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
	        	System.exit(0);
            }
        });
        
        pack();        
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        topTextArea.append(e.getActionCommand() + "\n");
    }

	//第二個Button的監聽器類。
	class Eavesdropper implements ActionListener {
    	public void actionPerformed(ActionEvent e) {
        	bottomTextArea.append("OK,"+e.getActionCommand() + "\n");
    	}
	}
	
	public static void main(String[] args){

 		MultiListener  m=new MultiListener("Multilistener example" );

	}
}