commad按键事件（初级问题）

[LichKingSZ]

import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.TextBox;
import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.*;

public class HelloWorld extends MIDlet {
private Display display;
private Form mainForm;
private final static Command cmdOK=new Command("确定",Command.SCREEN,1);
private TextBox textbox;

public HelloWorld() {
}

public void startApp() {
display=Display.getDisplay(this);

mainForm=new Form("演示窗体");
mainForm.append("这是一个标题。");

mainForm.addCommand(cmdOK);
display.setCurrent(mainForm);
}

public void pauseApp() {
}

public void destroyApp(boolean unconditional) {
}

public void commandAction(Command c, Displayable d) {
if (c == cmdOK) {
String text = "Go to the URL...";
Alert a = new Alert("URL", text, null, AlertType.INFO);
display.setCurrent(a);
}
}
}

为什么运行时，按键后没有反映？

[LichKingSZ]

我加上后报了这个错。。。

The method setCommandListener(CommandListener) in the type Displayable is not applicable for
the arguments (HelloWorld)

[luckycat]

HelloWorld 要实现 CommandListener 接口

[xueyong1203]

public class HelloWorld extends MIDlet implements CommandListener {
//your code
}

[贝壳鱼]

mainForm.setCommandListener(this);//把这句加到startApp()里面