android系统退出代码实现

   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);
	}
}