CardLayout布局练习（小的图片浏览器）

/*
涉及Panel中的图片的加载，还有Frame的关闭的方法， CardLayout（int hgap, int vgap）就会决定卡片面板的大小
匿名类的使用。。。
*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class CardLayoutDemo extends Frame{
   Panel pCards=new Panel();//卡片面板
   CardLayout Clayout=new CardLayout(120, 50);//设置卡片和面板边界的垂直和水平距离
   public CardLayoutDemo(){
         setLayout(new BorderLayout(100, 20));
         Panel pBtn = new Panel();//按钮面板

           pCards.setLayout(Clayout);
           //pCards.setPreferredSize(new Dimension(30,40));//这句不再起作用了：因为其父类CardLayoutDemo使用的是BorderLayout布局方式，会自动填充
           pCards.setBackground(Color.red);
           pBtn.setBackground(Color.yellow);
       pBtn.setLayout(new FlowLayout(FlowLayout.CENTER, 10, 10));
           pBtn.setPreferredSize(new Dimension(200, 50));

          Button tmpB;
       pBtn.add(tmpB = new Button("第一张"));
             tmpB.addActionListener(new myActionListener());
               tmpB.setActionCommand("first");
       pBtn.add(tmpB = new Button("下一张"));
             tmpB.addActionListener(new myActionListener());
               tmpB.setActionCommand("next");

       pBtn.add(tmpB = new Button("前一张"));
             tmpB.addActionListener(new myActionListener());
               tmpB.setActionCommand("previous");

       pBtn.add(tmpB = new Button("最后一张"));
             tmpB.addActionListener(new myActionListener());
               tmpB.setActionCommand("last");

       for(int i=1; i<=4; ++i){
              myPanel tmpP;
            pCards.add(""+i, tmpP=new myPanel(i){
                  public void paint(Graphics g){
              g.drawImage(new ImageIcon("zjy"+i+".jpg").getImage(), 20, 0, 300, 400, this);
             }
            });
              tmpP.setBackground(Color.blue);
              //tmpP.setSize(new Dimension(300, 400));//tmpP接受了匿名类对象，可以通过这种方法更改匿名类的属性
              //这里不设置的原因是它的大小由CardLayout(int hgap, int vgap)决定了
         }
           add(pBtn, "North");
           add(pCards, "Center");
   }
   class myActionListener implements ActionListener{
    public void actionPerformed(ActionEvent e){
       String str=e.getActionCommand();
       if(str.equals("first"))
           Clayout.first(pCards);
        else if(str.equals("next"))
           Clayout.next(pCards);
        else if(str.equals("previous"))
           Clayout.previous(pCards);
        else if(str.equals("last"))
           Clayout.last(pCards);
       }
    } 

    public static void main(String args[]){
       CardLayoutDemo myWindow = new CardLayoutDemo();
       myWindow.setSize(new Dimension(600, 600));
       myWindow.setResizable(false);
       myWindow.addWindowListener(new myClosingListener());
       myWindow.setVisible(true);
    }
}

class myClosingListener extends WindowAdapter{
   public void windowClosing(WindowEvent e){
      System.exit(0);
   }
}

class myPanel extends Panel{
   int i;
   public myPanel(int i){
      this.i=i;
   }
}