我在Canvas里为何不能drawImage？？？？

看我的原代码。
不能显示。

image.java

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class image extends MIDlet implements CommandListener {

Display display;
private MyCanvas canvas; //创建MyCanvas对象

private Command exitCommand = new Command("EXIT",Command.EXIT,0);

public image() {

display = Display.getDisplay(this);
canvas = new MyCanvas(this); //生成画布
canvas.addCommand(exitCommand);
canvas.setCommandListener(this);

}

public void startApp () {
display.setCurrent(canvas); //显示画布

}

public void destroyApp(boolean unconditional) {
}

public void pauseApp() {
}

public void commandAction(Command c, Displayable s) {
if(c == exitCommand)
destroyApp(true);
notifyDestroyed();
}
}

MyCanvas.java

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class MyCanvas extends Canvas{
private MIDlet midlet;
Image m_face;
int m_maxX = getWidth() - 1;
int m_maxY = getHeight() - 1;
int m_prevX = m_maxX/2;
int m_prevY = m_maxY/2;

public MyCanvas(MIDlet midlet){
this.midlet = midlet;
try{
m_face = Image.createImage("test.png");
}catch(Exception e){
m_face = null;
}
}

public void paint(Graphics g){
g.setColor(0xffffff);
g.fillRect(m_prevX - m_face.getWidth()/2,
m_prevY - m_face.getHeight()/2,
m_face.getWidth(),
m_face.getHeight());
g.setColor(0);

//画新图象
g.drawImage(m_face,0,0,Graphics.VCENTER | Graphics.HCENTER);
}
}

极盼高手赐教。谢谢！！！