android系统退出实现，代码如下：
package com.sms.util;import java.util.LinkedList;import java.util.List;import android.app.Activity;import android.app.Application;//实现Activity退出public class MyApplication extends Application{ private List<Activity> activityList = new LinkedList<Activity>(); private static MyApplication instance; private MyApplication(){ } //单例实现返回MyApplication实例 public static MyApplication getInstance(){ if(null == instance){ instance = new MyApplication(); } return instance; } //Activity加入到List中 public void addActivity(Activity activity){ activityList.add(activity); } //遍历每个Activity退出 public void exit(){ for(Activity activity:activityList){ activity.finish(); } System.exit(0); }}