一个例程不明白为什么?求教!
这是我调的一个程序,几个问题请教一下。
import java.util.Calendar;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
/**
*
* @author jn27
* @version
*/
public class SimpleGraphic extends MIDlet implements CommandListener{
private Command exitCommand;
private SimpleGraphicCanvas sg;
public SimpleGraphic(){
exitCommand=new Command("Exit",Command.EXIT, 1);
sg=new SimpleGraphicCanvas();
sg.addCommand(exitCommand);
sg.setCommandListener(this);
Display.getDisplay(this).setCurrent(sg);
}
public void startApp() {
}
public void pauseApp() {
}
public void destroyApp(boolean arg0) {
}
public void commandAction(Command c,Display d){//为何这里报错说SimpleGraphic是个抽象类,不能覆写commandAction()?我明明是继承了接口CommandListener啊?
if(c==exitCommand){
destroyApp(false);//为何这里报错??
notifyDestroyed();
}
}
}
class SimpleGraphicCanvas extends Canvas{
protected void paint(Graphics g){
g.drawLine(0,0, 50,50);
g.drawRect(60,60, 50, 80);
g.fillRect(65,65, 30,40);
}
}