commandevent_midlet.java

《J2ME无线移动游戏开发》一书的配套光盘

package ch04;

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

public class CommandEvent_MIDlet
    extends MIDlet
    implements CommandListener {

  //声明一个Display对象
  Display display;

  //声明一个List列表对象
  List menu;

  //声明三个代表图标的对象
  Image aimage, bimage, cimage;

  //创建两个按钮
  Command backCommand = new Command("返回", Command.BACK, 0);
  Command exitCommand = new Command("退出", Command.STOP, 2);

  /*
   1.构造器
   */
  public CommandEvent_MIDlet() {
    display = Display.getDisplay(this);
    try {
      aimage = Image.createImage("/icons/background/star.png");
      bimage = Image.createImage("/icons/background/hand.png");
      cimage = Image.createImage("/icons/background/boot.png");
    }
    catch (Exception e) {
      System.out.println(e.getMessage());
    }
    menu = new List("菜单", Choice.IMPLICIT);
    menu.append("选项1", aimage);
    menu.append("选项2", bimage);
    menu.append("选项3", cimage);
    display.setCurrent(menu);

    menu.addCommand(exitCommand);
    menu.setCommandListener(this);
  }

  /*
   2.响应按钮事件
   */
  public void commandAction(Command c, Displayable d) {
    String label = c.getLabel();
    if (label.equals("退出")) {
      destroyApp(true);
    }
    else if (label.equals("返回")) {
      display.setCurrent(menu);
    }
    else {
      List down = (List) display.getCurrent();
      switch (down.getSelectedIndex()) {
        case 0:
          prepare("选项1");
          break;
        case 1:
          prepare("选项2");
          break;
        case 2:
          prepare("选项3");
          break;
      }

    }
  }

  /*
   3.返回提示信息
   */
  public void prepare(String sn) {
    Alert currentAlert = new Alert("用户选择提示信息：");
    currentAlert.setString("提示：您选择了" + sn + "！");
    currentAlert.setTimeout(Alert.FOREVER);
    currentAlert.addCommand(backCommand);
    currentAlert.setCommandListener(this);
    display.setCurrent(currentAlert);
  }

  //启动应用程序
  public void startApp() throws MIDletStateChangeException {
  }

  //挂起应用程序
  public void pauseApp() {
    display = null;
    menu = null;
  }

  //撤销应用程序
  public void destroyApp(boolean unconditional) {
    notifyDestroyed();
  }
}