/*****************************************
展示JComboBox
*************************************************/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
public class ui29 extends JFrame implements ActionListener,ItemListener 
{
    Container c;
    JButton bot0,bot1;
    Color pencolor[]=new Color[5];
    String[] cname={"白色","綠色","藍色","紅色","黃色"} ;
    JComboBox cbox;
    int cpt=0;
    int clear_mode=1;//一開始先清除畫面
    int now_x=0,now_y=0;
    public ui29()
    {
        super("JComboBox展示");
        int i;
        int x;
        c=getContentPane();
        pencolor[0]=Color.white;
        pencolor[1]=Color.green;
        pencolor[2]=Color.blue;
        pencolor[3]=Color.red;
        pencolor[4]=Color.yellow;
        c.setLayout(new FlowLayout(FlowLayout.CENTER));
        cbox=new JComboBox(cname);// 設定選項
        bot0=new JButton("結束");
        bot1=new JButton("清除");
        c.add(bot0);
        c.add(bot1);
        c.add(cbox);
        cbox.addItemListener(this);//設定顏色選擇
        bot0.addActionListener(this);
        bot1.addActionListener(this);
        addMouseMotionListener(new checkmouse());//設定滑鼠
        setSize(350,500);
        setVisible(true);
    }
    public void paint(Graphics g)
    {
        if (clear_mode==1)   super.paint(g);
        g.setColor(pencolor[cpt]);
        g.drawLine(now_x,now_y,now_x,now_y);
    }

    /***按鈕事件的傾聽方法****/
    public void actionPerformed(ActionEvent e) //按鈕事件的處理方法
    { 
        if (e.getSource()==bot0)
        {
            System.exit(0);
        }
        else if (e.getSource()==bot1)
        {
            clear_mode=1;
        }//bot1
        repaint();
    }
    public void itemStateChanged(ItemEvent e)
    {
        cpt=cbox.getSelectedIndex();//看看選到哪一個就設定顏色
        repaint();    
    }
    /*****實作滑鼠移動事件處理物件 *******/
    class checkmouse extends MouseMotionAdapter
    {
        public void mouseDragged(MouseEvent e)
        { 
            now_x=e.getX();
            now_y=e.getY();
            clear_mode=0;//開始畫圖，不可以清掉舊資料
            repaint(); //重新顯示一次
        }	
    }//checkmouse 
    public static void main(String args[]) //程式起點
    {
        ui29 app=new ui29(); //畫圖
        //處理視窗關閉要求
        app.addWindowListener(
             new WindowAdapter()
             {
                public void windowClosing(WindowEvent e)
                {  System.exit(0);}
             });
    }
}