请问下面代码在WTK的模拟器中都可以运行,但为何在7210上运行后一直是"正在打开程序"?请专家帮忙。
package showmap;

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

public class ShowMapMIDlet extends MIDlet implements CommandListener{
private static ShowMapMIDlet instance;
String[] litem={"1","2","3","4"};
List l;
/** Constructor */
public ShowMapMIDlet() {
l=new List("定位方式:",List.IMPLICIT,litem,null);
instance = this;
}

/** Main method */
public void startApp() {
Display.getDisplay(this).setCurrent(l);
}

/** Handle pausing the MIDlet */
public void pauseApp() {
}

/** Handle destroying the MIDlet */
public void destroyApp(boolean unconditional) {
}

/** Quit the MIDlet */
public static void quitApp() {
instance.destroyApp(true);
instance.notifyDestroyed();
instance = null;
}
public void commandAction(Command command, Displayable displayable) {
/** @todo Add command handling code */

}

}