android连续按两次返回退出程序

    Timer tExit = new Timer(); 

     private static Boolean hasTask = false;    

     TimerTask task = new TimerTask() {                    

public void run() {             

 UserHelper.setIsExit(false);   

          hasTask = true;       

   }     

 };

 public boolean onKeyDown(int keyCode, KeyEvent event)

{   

if (keyCode == KeyEvent.KEYCODE_BACK)

{    if (!UserHelper.getIsExit())

{     UserHelper.setIsExit(true);     

UserHelper.AlertShort(Login.this, "再按一次退出十步芳草");   

  if (!hasTask)

{      tExit.schedule(task, 2000);    

 }   

 }    

else {

    UserHelper.setIsExit(false);     finish();     System.exit(0);    

}   }  

 return true;  }

 

UserHelper类声明一个字段

 private static  Boolean isExit = false;

 public static Boolean getIsExit() {   return isExit;  }

 public static void setIsExit(Boolean isExit) {   UserHelper.isExit = isExit;  }