.Net Micro Framework研究—数据的永久存储

.Net Micro Framework不支持文件系统(目前该项功能正在研发之中),所以无法像Windows和windows ce平台那样把需要永久保存的数据保存到文件之中。内存中保存的数据只要系统一掉电,所有的数据也都消失了,这对一些需要保存参数的应用来说真是不妙。
这几天在研究MF触摸屏功能时就遇到该问题,因为触摸屏校准之后,需要保存校准后的参数,否则MF一重启,难道还需要重新校准不成?
 感谢Donald Thompson 和 Rob S. Miles,从他们的大作上找到了问题的解决办法。办法就是把对象保存到Flash(EEPROM)中(有点像对象的二进制序列化)。
下面是我整理的示例代码(实现比较简单,但总觉得不太正规,不知道能存多大,也搞不清楚数据到底存放在什么位置了。):

using System;
using Microsoft.SPOT;
using System.Collections;
using System.Threading;
 
namespace DataStorage
{
    public class Program
    {      
        public static void Main()
        {
            FlashDatas fd = FlashDatas.Load();
            fd.dump();
            fd.Flag = "adfg";
            //fd.Items.Clear();               
            //fd.AddItem(new FlashData(55, "1aaa"));
            //fd.AddItem(new FlashData(66, "2bbb"));
            //fd.AddItem(new FlashData(77, "3ccc"));
            //fd.AddItem(new FlashData(88, "4ddd"));
            fd.Save();
            Thread.Sleep(3000);            
        }
 
        [Serializable]
        private class FlashData
        {
            public DateTime date;
            public int iData;
            public string sData;
            public FlashData(int iData, string sData)
            {
                date = DateTime.Now;
                this.iData = iData;
                this.sData = sData;
            }
 
            public override string ToString()
            {
                return date.ToString() + " " + iData.ToString() + " " + sData;
            }
        }
 
        [Serializable]
        private class FlashDatas
        {
            public DateTime CreateTime = DateTime.Now;
            public string Flag = @"http://blog.csdn.net/yefanqiu/";
            public ArrayList Items = new ArrayList();
 
            public void dump()
            {
                Debug.Print(CreateTime.ToString());
                Debug.Print(Flag);
                foreach (FlashData Item in Items)
                {
                    if (Item != null)
                    {
                        Debug.Print(Item.ToString());
                    }
                }
            }
            public void AddItem(FlashData Item)
            {
                Items.Add(Item);
            }
 
            //调入数据
            public static FlashDatas Load()
            {
                ExtendedWeakReference ewr = ExtendedWeakReference.RecoverOrCreate(
                        typeof(FlashDatas),                       //类型,任意类都可以,其名称起到一个索引作用
                        0,                                        //ID号,这个数据比较有用,不同ID号代表不同数据
                        ExtendedWeakReference.c_SurvivePowerdown);//该标志和.c_SurviveBoot 区别不大
                ewr.Priority = (Int32)ExtendedWeakReference.PriorityLevel.Important;
 
                FlashDatas data = ewr.Target as FlashDatas;
                if (data == null)
                {
                    data = new FlashDatas();
                }
                return data;
            }        
 
            //保存数据
            public void Save()
            {
                ExtendedWeakReference ewr = ExtendedWeakReference.RecoverOrCreate(typeof(FlashDatas), 0, ExtendedWeakReference.c_SurvivePowerdown);
                ewr.Priority = (Int32)ExtendedWeakReference.PriorityLevel.Important;
                ewr.Target = this;
            }
        }
    }
}

以上代码在Digi开发板上测试成功,断电之后,再上电,保存的数据确实没有丢失。
MSDN中相关函数的说明如下:
ExtendedWeakReference Members
The following tables list the members exposed by the ExtendedWeakReference type.
Public Constructors
.Net Micro Framework研究—数据的永久存储

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