simple_tone_midlet.java

本光盘是《J2ME无线移动游戏开发》一书的配套光盘

package ch11;

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

public class Simple_Tone_MIDlet
    extends MIDlet
    implements CommandListener {

  //声明一个Display对象
  private Display mDisplay;

  //声明一个Form对象
  private Form mMainForm;

  //声明一个播放按钮Command对象
  private Command mPlayCommand;

  //声明一个接收音符的文本域对象
  private TextField mNoteField;

  //声明一个接收播放时间的文本域对象
  private TextField mDurationField;

  //声明一个接收音量的文本域对象
  private TextField mVolumeField;

  /*
   1.构造器
   */
  public Simple_Tone_MIDlet() {
    mMainForm = new Form("一个单音播放器");
    mNoteField = new TextField("音符: ", "60", 8, TextField.NUMERIC);
    mMainForm.append(mNoteField);
    mDurationField = new TextField("时间: ", "500", 8, TextField.NUMERIC);
    mMainForm.append(mDurationField);
    mVolumeField = new TextField("音量: ", "50", 8, TextField.NUMERIC);
    mMainForm.append(mVolumeField);

    mPlayCommand = new Command("播放", Command.SCREEN, 0);
    mMainForm.addCommand(mPlayCommand);
    mMainForm.addCommand(new Command("退出", Command.EXIT, 0));
    mMainForm.setCommandListener(this);

    mDisplay = Display.getDisplay(this);
    mDisplay.setCurrent(mMainForm);
  }

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

  //挂起应用程序
  public void pauseApp() {
  }

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

  /*
   2.响应按钮事件
   */
  public void commandAction(Command c, Displayable s) {
    if (c.getCommandType() == Command.EXIT) {
      destroyApp(true);
      notifyDestroyed();
    }
    else if (c == mPlayCommand) {
      try {
        int note = Integer.parseInt(mNoteField.getString());
        int duration = Integer.parseInt(mDurationField.getString());
        int volume = Integer.parseInt(mVolumeField.getString());
        Manager.playTone(note, duration, volume);
      }
      catch (Throwable t) {
        Alert a = new Alert("警告：", t.toString(),
                            null, AlertType.ERROR);
        mDisplay.setCurrent(a, mMainForm);
      }
    }
  }
}