displayalert.java

利用J2ME显示ALERT的实例

package thesixth;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class DisplayAlert extends MIDlet implements CommandListener
{
  private Display display;
  private Alert alert;
  private Form form;
  private Command exit;
  private boolean exitFlag;
  public DisplayAlert()
  {
    exitFlag=false;
    display=Display.getDisplay(this);    
    exit=new Command("Exit",Command.SCREEN,1);
    form=new Form("Throw Exception");    
    form.addCommand(exit);
    form.setCommandListener(this);   
  }
  public void startApp()
  {
    display.setCurrent(form);
  }
  public void pauseApp()
  {
  }
  public void destroyApp(boolean unconditional) throws MIDletStateChangeException
  {
    if (unconditional==false)
    {
      throw new MIDletStateChangeException();
    }
  }
  public void commandAction(Command command,Displayable displayable)
  {
    if (command==exit)
    {
      try
      {
        if (exitFlag==false)
        {
          alert=new Alert("Busy","Please try again.",null,AlertType.WARNING);
          alert.setTimeout(Alert.FOREVER);
          display.setCurrent(alert,form);
          destroyApp(false);
        }
        else
        {
          destroyApp(true);
          notifyDestroyed();
        }
      }
      catch (MIDletStateChangeException exception)
      {
        exitFlag=true;
      }
    }
  }
}