ui_low1.java

J2ME 无线通信技术应用开发源代码

// 程序名UI_Low1.java
// 一个简单的MIDlet类，用来调用Canvas的子类
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class UI_Low1 extends MIDlet implements CommandListener {
  private Display  display;
  private MyCanvas canvas;
  private Command cmdExit;
  private Command cmdAlert;
  private Alert alert;
   
  public UI_Low1(){
    display = Display.getDisplay( this );
    canvas  = new MyCanvas( this );
    cmdExit = new Command("Exit",Command.SCREEN,1);
    cmdAlert = new Command("Alert",Command.SCREEN,1);
    alert = new Alert("alert!","Is this alert simple?",null,AlertType.INFO);
    alert.setTimeout(5000);
    canvas.addCommand(cmdExit);
    canvas.addCommand(cmdAlert);
    canvas.setCommandListener(this);
  }

  protected void startApp(){
    display.setCurrent( canvas );
  }
   
  protected void pauseApp(){
  }
  
  protected void destroyApp( boolean unconditional ){
  }

  public void commandAction( Command c, Displayable d ){
    if( c == cmdAlert){
      System.out.println("Before alert called.");
      System.out.println("isShown() : "+canvas.isShown());
      display.setCurrent(alert,display.getCurrent());
      System.out.println("After alert called.");
      System.out.println("isShown() : "+canvas.isShown());
    }
    if( c == cmdExit){
      exit();
    }
  }

  public void exit(){
    destroyApp( true );
    notifyDestroyed();
  }
}