彻底退出android程序的方法

package com.cqupt.util;
import java.util.LinkedList;
import java.util.List;

import android.app.Activity;
import android.app.Application;

public class ExitApplication extends Application {

private List<Activity> activityList = new LinkedList();
private static ExitApplication instance;

private ExitApplication()
{
}
//单例模式中获取唯一的ExitApplication实例
public static ExitApplication getInstance()
{
if(null == instance)
{
instance = new ExitApplication();
}
return instance;

}
//添加Activity到容器中
public void addActivity(Activity activity)
{
activityList.add(activity);
}
//遍历所有Activity并finish

public void exit()
{

for(Activity activity : activityList)
{
activity.finish();
}

System.exit(0);

}
}

ExitApplication.getInstance().addActivity(this);

if (!isExit) {
Toast.makeText(MoreActivity.this, "再点一次退出程序", Toast.LENGTH_SHORT).show();
isExit = true;
}else{
ExitApplication.getInstance().exit();
}