画图工具画不出来，求教！

/************************************************************************************************************/
public class DrawMain extends JFrame{
//Main Method
public static void main(String[] args) {
J_ButtonPanel btPanel = new J_ButtonPanel();
J_PaintingGround ptGround = new J_PaintingGround(btPanel);
DrawMain app = new DrawMain(btPanel, ptGround);

app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
app.setSize(600, 600);
app.setVisible(true);

//设置显示外观
try{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}catch(Exception e) {
e.printStackTrace();
}
}

//构造函数
public DrawMain(J_ButtonPanel btPanel, J_PaintingGround ptGround) {
//设置容器及容器的整体布局
super("画板例程");
Container cp = getContentPane();

cp.add(btPanel.getPanel(),BorderLayout.WEST);
cp.add(ptGround, BorderLayout.CENTER);
}
}
/************************************************************************************************************/
public class J_ButtonPanel extends JPanel implements ActionListener{
private int optype = 0; //操作类型变量，默认值为0
private JPanel buttonPanel = new JPanel(); //按钮版
public JPanel getPanel(){return buttonPanel;} //获取按钮版
public int getOptype(){return optype;} //获取操作类型
J_ButtonPanel() {
//新建按钮
btFree = new JButton("随手画");
btLine = new JButton("直线");
btRectangle = new JButton("矩形");
btRound = new JButton("圆");
btEllipse = new JButton("椭圆");
btFill = new JButton("填充");
btSave = new JButton("保存");
btOpen = new JButton("打开");
//添加按钮
buttonPanel.add(btOpen);
buttonPanel.add(btSave);
buttonPanel.add(btFree);
buttonPanel.add(btLine);
buttonPanel.add(btRectangle);
buttonPanel.add(btRound);
buttonPanel.add(btEllipse);
buttonPanel.add(btFill);
}

public void actionPerformed(ActionEvent event) { //鼠标监听器
Object source = event.getSource(); //获取动作，确定操作类型
if(source == btFree) optype = 0;
if(source == btLine) optype = 1;
if(source == btRectangle) optype = 2;
if(source == btRound) optype = 3;
if(source == btEllipse) optype = 4;
if(source == btFill) optype = 5;
if(source == btOpen) optype = 6;
if(source == btSave) optype = 7;
}

private JButton btFree;
private JButton btLine;
private JButton btRectangle;
private JButton btRound;
private JButton btEllipse;
private JButton btFill;
private JButton btSave;
private JButton btOpen;
}
/************************************************************************************************************/
public class J_PaintingGround extends JPanel{
public Vector<Vector<Integer>> m_vectorSet = new Vector<Vector<Integer>>(); //设置变量存放笔画

public J_PaintingGround(J_ButtonPanel buttonpanel) { //构造函数
btPanel = buttonpanel; //按钮版

if(btPanel.getOptype() == 0){
addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent event)
{
Vector<Integer> v = new Vector<Integer>();
v.add(btPanel.getOptype());
v.add(event.getX());
v.add(event.getY());
m_vectorSet.add(v);
}
}
);
addMouseMotionListener(new MouseMotionListener()
{
public void mouseMoved(MouseEvent event){}

public void mouseDragged(MouseEvent event)
{
int n = m_vectorSet.size()-1;
Vector<Integer> v = new Vector<Integer>();
v = m_vectorSet.get(n);
v.add(event.getX());
v.add(event.getY());
repaint();
}
}
);
}
if(btPanel.getOptype() >=1 && btPanel.getOptype() <= 4){
addMouseListener(new MouseAdapter()
{
Vector<Integer> v = new Vector<Integer>();
public void mousePressed(MouseEvent event)
{
v.add(btPanel.getOptype());
v.add(event.getX());
v.add(event.getY());
}
public void mouseReleased(MouseEvent event)
{
v.add(event.getX());
v.add(event.getY());
m_vectorSet.add(v);
repaint();
}
}
);
}
if(btPanel.getOptype() == 5){}
if(btPanel.getOptype() == 7){
try
{
FileOutputStream f = new FileOutputStream("绘画作品.txt");
DataOutputStream fout = new DataOutputStream(f);
int i,j,m;
int n = m_vectorSet.size();
Vector<Integer> vv = new Vector<Integer>();
for(i=0;i<n;i++)
{
vv = m_vectorSet.get(i);
m = vv.size()-1;
for(j=0; j<m; j++)
{
fout.writeInt(vv.get(j).intValue());
}
fout.writeInt('\n');
}
fout.close();
repaint();
}
catch(Exception e)
{
System.err.println("发生异常：" + e);
e.printStackTrace();
}
}

if(btPanel.getOptype() == 6){
try
{
int i,j,k=0;
RandomAccessFile f = new RandomAccessFile("绘画作品.txt","r");
Vector<Vector> v = new Vector<Vector>();
Vector<Integer> vv = new Vector<Integer>();

for(i=0;i<f.length()/4-1;i++)
{
if(f.readInt() == '\n'){
v.add(vv);
vv = new Vector<Integer>();
}
else {
f.seek(i*4);
vv.add(f.readInt());
}
}
this.repaint();
}
catch(Exception e)
{
System.err.println("发生异常：" + e);
e.printStackTrace();
}
}
}

protected void paintComponent(Graphics g)
{
g.setColor(Color.YELLOW);
g.clearRect(0, 0, getWidth(), getHeight());
Vector<Integer> v = new Vector<Integer>();
Point s, t;
int i, j, m;
int n = m_vectorSet.size();
for(i=0,j=0; i<n; i++)
{
v = m_vectorSet.get(i);
Integer a = v.get(0);
v.remove(0);
m = v.size()-1;
switch(a.intValue())
{
case FREE:
while(j+3<m){
s = new Point(v.get(j).intValue(),v.get(j+1).intValue());
t = new Point(v.get(j+2).intValue(),v.get(j+3).intValue());
g.drawLine(s.x, s.y, t.x, t.y);
j=j+2;
}
break;
case LINE:
s = new Point(v.get(j++).intValue(),v.get(j++).intValue());
t = new Point(v.get(j++).intValue(),v.get(j++).intValue());
g.drawLine(s.x, s.y, t.x, t.y);
break;
case ROUND:
s = new Point(v.get(j++).intValue(),v.get(j++).intValue());
t = new Point(v.get(j++).intValue(),v.get(j++).intValue());
g.drawRoundRect(s.x, s.y, t.x-s.x, t.x-s.x, t.x-s.x, t.x-s.x);
break;
case RECTANGLE:
s = new Point(v.get(j++).intValue(),v.get(j++).intValue());
t = new Point(v.get(j++).intValue(),v.get(j++).intValue());
g.drawRect(s.x, s.y, t.x-s.x, t.y-s.y);
break;
case ELLIPSE:
s = new Point(v.get(j++).intValue(),v.get(j++).intValue());
t = new Point(v.get(j++).intValue(),v.get(j++).intValue());
g.drawOval(s.x, s.y, t.x-s.x, t.y-s.y);
break;
default:break;
}
}
}

public Dimension getPreferredSize()
{
return new Dimension(600,600);
}

private int optype;
private J_ButtonPanel btPanel = new J_ButtonPanel();

public static final int FREE = 0;
public static final int LINE = 1;
public static final int RECTANGLE = 2;
public static final int ROUND = 3;
public static final int ELLIPSE = 4;
public static final int FILL = 5;
public static final int OPEN = 6;
public static final int SAVE = 7;
}
/************************************************************************************************************/
运行通过，但是无法在画图版上画图，按钮没反应。