commandmidlet.java

J2ME初学者必作的CANVAS练习

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
// MIDlet类作为CommandListener的实现类
public class CommandMIDlet extends MIDlet 
	implements CommandListener {
  
  private Display display;  
  private GCanvas canvas;//声明GCanvas对象
  
  
  Command command1 = new Command("文字1", Command.OK, 0);
  Command command2 = new Command("文字2", Command.OK, 1);
  Command command3 = new Command("文字3", Command.OK, 2);
   //声明并创建4个command对象
  
public void startApp() {
	if (display==null)
		display = Display.getDisplay(this);	
    if (canvas == null){
      canvas = new GCanvas();//创建GCanvas对象
	  Command exitCommand = 
	                new Command("退出", Command.EXIT, 0);//左下角菜单栏显示退出按钮
	  canvas.addCommand(exitCommand);//加入Command对象
	  canvas.addCommand(command1);
	  canvas.addCommand(command2);
	  canvas.addCommand(command3);
	  //OCanvas对象作为事件源
	  canvas.setCommandListener(this);
	}
    display.setCurrent(canvas);//显示GCanvas对象     
  }
  
  public void pauseApp() {}
  
  public void destroyApp(boolean unconditional) {}
  //CommandMIDlet需要实现commandAction方法
 
  //判断command的类型；或判断对象是否相等
  public void commandAction(Command c, Displayable d) {
    if (c.getCommandType() == Command.EXIT) {
      destroyApp(true);//退出本MIDlet
      notifyDestroyed();
	  return;
    }
	if (c==command1) {
	  TextBox txt1=new TextBox("实验中1","This is my second MIDlet",256,0);
		display.setCurrent(txt1);
                     return;//显示一段信息之后退出
	}
       
        if (c==command2) {TextBox txt2=new TextBox("实验中2","Do you think it is a good work?",256,0);
		display.setCurrent(txt2);
                     return;}
	if (c==command3) {display.setCurrent(new Alert("Thank you for watching"),canvas);
	  return;}
  }
}