为什么不能动态的画图
package   chapter8;

import   java.awt.*;
import   java.awt.geom.*;
import   java.awt.event.*;
import   javax.swing.*;
import   javax.swing.event.*;

class   ClockPanel   extends   JPanel{
private   double   minutes=0;
private   int   RADIUS=100;
private   double   MINUTE_HAND_LENGTH=0.8*RADIUS;
private   double   HOUR_HAND_LENGTH=0.6*RADIUS;
public   ClockPanel(){
setPreferredSize(new   Dimension(2*RADIUS+1,2*RADIUS+1));
}

public   void   paintComponent(Graphics   g){
super.paintComponent(g);
Graphics2D   g2=(Graphics2D)g;

Ellipse2D   circle=new   Ellipse2D.Double(0,0,2*RADIUS,2*RADIUS);
g2.draw(circle);

double   hourAngle=Math.toRadians(90-360*minutes/(12*60));
drawHand(g2,hourAngle,HOUR_HAND_LENGTH);

double   minuteAngle=Math.toRadians(90-360*minutes/60);
drawHand(g2,minuteAngle,MINUTE_HAND_LENGTH);

}

public   void   drawHand(Graphics2D   g2,double   angle,double   handLength){
Point2D   end=new   Point2D.Double(
RADIUS+handLength*Math.cos(angle),
RADIUS-handLength*Math.sin(angle)
);
Point2D   center=new   Point2D.Double(RADIUS,RADIUS);
g2.draw(new   Line2D.Double(center,end));

}

public   void   setTime(int   h,int   m){
minutes=h*60+m;
repaint();
System.out.println( "error ");
}
}

class   TextPanel   extends   JPanel{

}

class   TextFrame   extends   JFrame{
private   static   final   int   DEAULT_WIDTH=300;
private   static   final   int   DEAULT_HEIGHT=300;
private   JTextField   hourField;
private   JTextField   minuteField;
private   ClockPanel   clock;

public   TextFrame(){
DocumentListener   listener=new   ClockFieldListener();

JPanel   text=new   JPanel();

text.add(new   JLabel( "Hours: "));
hourField=new   JTextField( "12 ",3);
text.add(hourField);
hourField.getDocument().addDocumentListener(listener);


text.add(new   JLabel( "Minutes: "));
minuteField=new   JTextField( "00 ",3);
text.add(minuteField);
minuteField.getDocument().addDocumentListener(listener);

clock=new   ClockPanel();

add(clock,BorderLayout.SOUTH);
add(text,BorderLayout.CENTER);

pack();
}

public   void   setClock(){
try{
int   hours=Integer.parseInt(hourField.getText().trim());
int   minutes=Integer.parseInt(minuteField.getText().trim());
clock.setTime(hours,   minutes);
System.out.println( "error ");
}
catch(NumberFormatException   e){
System.out.println( "error2 ");
}
}

private   class   ClockFieldListener   implements   DocumentListener{
public   void   changedUpdate(DocumentEvent   event){
}
public   void   insertUpdate(DocumentEvent   event){
setClock();
}
public   void   removeUpdate(DocumentEvent   event){
setClock();
}
}
}

public   class   TextTest{
public   static   void   main(String[]   args){