j2me学习笔记【5】——抛出异常处理的小例子

抛出异常处理，当按第二次退出，才真正退出。

package mtk;import javax.microedition.lcdui.Command;import javax.microedition.lcdui.CommandListener;import javax.microedition.lcdui.Display;import javax.microedition.lcdui.Displayable;import javax.microedition.lcdui.Form;import javax.microedition.lcdui.StringItem;import javax.microedition.midlet.MIDlet;import javax.microedition.midlet.MIDletStateChangeException;public class ThrowException extends MIDlet implements CommandListener {private Display display;private Form mainForm;private final static Command CMD_EXIT=new Command("退出",Command.EXIT,1);private boolean isSafeToQuit;public ThrowException() {isSafeToQuit=false;display=Display.getDisplay(this);mainForm=new Form("抛出异常");mainForm.addCommand(CMD_EXIT);mainForm.setCommandListener(this);}protected void destroyApp(boolean unconditional) throws MIDletStateChangeException {if(unconditional==false){throw new MIDletStateChangeException();}}protected void pauseApp() {}protected void startApp() throws MIDletStateChangeException {display.setCurrent(mainForm);}public void commandAction(Command c, Displayable d) {if(c==CMD_EXIT){try {if(isSafeToQuit==false){StringItem msg=new StringItem("忙","重试");mainForm.append(msg);destroyApp(false);}else{destroyApp(true);notifyDestroyed();}} catch (MIDletStateChangeException e) {isSafeToQuit=true;}}}}