点击’Details'报异常：java.lang.NullPointerException，JB2006下编译通
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?JB2006下编译通过，但是NOKIA7210模拟器环境运行时出现“Application Eorrer”，点击“Details”出现异常报告：java.lang.NullPointerException?
代码如下：
?ok3.java???
??
? package ok3;
?
? import javax.microedition.lcdui.Canvas;
? import javax.microedition.lcdui.Display;
? import javax.microedition.midlet.MIDlet;
? import javax.microedition.midlet.MIDletStateChangeException;
?
?
? public class ok3 extends MIDlet {
? private Canvas canvas;
? private Display display;
?
? static ok3 instance;
? ok3Displayable displayable = new ok3Displayable();
? public ok3() {
? instance = this;
? }
?
? public void startApp() throws MIDletStateChangeException {
? display = Display.getDisplay(this);
? canvas = new ok3Displayable();
? display.setCurrent(canvas);
?
? }
?
? public void pauseApp() {
? }
?
? public void destroyApp(boolean bool) {
? }
?
? public static void quitApp() {
? instance.destroyApp(true);
? instance.notifyDestroyed();
? instance = null;
? }
?
? }
?
?
?
? ==================
? ok3Displayable
? ==================
?
? package ok3;
?
? import javax.microedition.lcdui.*;
? import javax.microedition.midlet.*;
? import java.util.*;
? import java.io.*;
?
? public class ok3Displayable extends Canvas implements CommandListener {
?
?
? public ok3Displayable() {
? try {
? jbInit();
? }
? catch(Exception e) {
? e.printStackTrace();
? }
? }
?
? private void jbInit() throws Exception {
? setCommandListener(this);
? addCommand(new Command("Exit", Command.EXIT, 1));
? }
?
? public void commandAction(Command command, Displayable displayable) {
? if (command.getCommandType() == Command.EXIT) {
? ok3.quitApp();
? }
? }
? private Image kk = null;
? public void ok3Displayable(){
? try {
? kk = Image.createImage("/ohyeah.png");
? }
? catch(IOException e) {
? e.printStackTrace();
? }
? }
? protected void paint(Graphics g) {
? g.setColor(221, 71, 71); // red
