文件系统: 文本的读写, 二进制的读写, 流的读写, 最近访问列表和未来访问列表

演示如何读写文本数据

• 演示如何读写二进制数据
• 演示如何读写流数据
• 演示如何读写“最近访问列表”和“未来访问列表”

1、演示如何读写文本数据

<StackPanel Margin="0,50 ">

            <Button Name="btnWriteText" Content="Text方式写入文件" Click="btnWriteText_Click" Margin="5"></Button>
            <Button Name="btnReadText" Content="Text方式读取文件" Click="btnReadText_Click" Margin="5"></Button>
       
            <TextBlock Name="lblMsg" Margin="5"></TextBlock>
      
            
        </StackPanel>

FileSystem/ReadWriteText.xaml.cs

/*
 * 演示如何读写文本数据
 * 注：如果需要读写某扩展名的文件，需要在 Package.appxmanifest 增加“文件类型关联”声明，并做相应的配置
 * 
 * StorageFolder - 文件夹操作类
 *     获取文件夹相关属性、重命名、Create...、Get...等
 * 
 * StorageFile - 文件操作类
 *     获取文件相关属性、重命名、Create...、Get...、Copy...、Move...、Delete...、Open...、Replace...等
 *     
 * FileIO - 用于读写 IStorageFile 对象的帮助类
 *     WriteTextAsync() - 将指定的文本数据写入到指定的文件
 *     AppendTextAsync() - 将指定的文本数据追加到指定的文件
 *     WriteLinesAsync() - 将指定的多行文本数据写入到指定的文件
 *     AppendLinesAsync() - 将指定的多行文本数据追加到指定的文件
 *     ReadTextAsync() - 获取指定的文件中的文本数据
 *     ReadLinesAsync() - 获取指定的文件中的文本数据，返回的是一行一行的数据
 *     
 * 注：WinRT 中的关于存储操作的相关类都在 Windows.Storage 命名空间内
 */

using System;
using Windows.Storage;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace XamlDemo.FileSystem
{
    public sealed partial class ReadWriteText : Page
    {
        public ReadWriteText()
        {
            this.InitializeComponent();
        }

private async void btnWriteText_Click(object sender, RoutedEventArgs e)
        {
            //在指定的目录下创建指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;// KnownFolders.DocumentsLibrary;
            StorageFile storageFile = await storageFolder.CreateFileAsync("abc.txt",CreationCollisionOption.ReplaceExisting);

            //在指定的文件中写入指定的文本
            string textContent = "I am wangma";
            await FileIO.WriteTextAsync(storageFile,textContent,UnicodeEncoding.Utf8);

            lblMsg.Text = "写入成功";
        }

        private async void btnReadText_Click(object sender, RoutedEventArgs e)
        {
            //在指定的目录下获取指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;
            try
            {
                StorageFile storageFile = await storageFolder.GetFileAsync("abc.txt");
                if (storageFile != null)
                {
                    //获取指定的文件中的文本内容
                    string textContent = await FileIO.ReadTextAsync(storageFile, UnicodeEncoding.Utf8);
                    lblMsg.Text = "读取结果：" + textContent;
                }
            }
            catch(Exception ex)
            {
                lblMsg.Text = "读取失败：" + ex;
            }
          
        }

    }
}

2、演示如何读写二进制数据

 <StackPanel Margin="0 50">

            <Button Name="btnWriteBinary" Content="Binary方式写入" Margin="5" Click="btnWriteBinary_Click"></Button>
            <Button Name="btnReadBinary" Content="Binary方式读取" Margin="5" Click="btnReadBinary_Click"></Button>
            <TextBlock Name="lblMsg" Margin="5"></TextBlock>       
        </StackPanel>

FileSystem/ReadWriteBinary.xaml.cs

/*
 * 演示如何读写二进制数据
 * 注：如果需要读写某扩展名的文件，需要在 Package.appxmanifest 增加“文件类型关联”声明，并做相应的配置
 * 
 * StorageFolder - 文件夹操作类
 *     获取文件夹相关属性、重命名、Create...、Get...等
 * 
 * StorageFile - 文件操作类
 *     获取文件相关属性、重命名、Create...、Get...、Copy...、Move...、Delete...、Open...、Replace...等
 *     
 * FileIO - 用于读写 IStorageFile 对象的帮助类
 *     WriteBufferAsync() - 将指定的二进制数据写入指定的文件
 *     ReadBufferAsync() - 获取指定的文件中的二进制数据
 *     
 * IBuffer - WinRT 中的字节数组
 *     
 * 注：WinRT 中的关于存储操作的相关类都在 Windows.Storage 命名空间内
 */

using System;
using Windows.Storage;
using Windows.Storage.Streams;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace XamlDemo.FileSystem
{
    public sealed partial class ReadWriteBinary : Page
    {
        public ReadWriteBinary()
        {
            this.InitializeComponent();
        }

private async void btnWriteBinary_Click(object sender, RoutedEventArgs e)
        {
            //在指定的目录下创建指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;
            StorageFile storageFile =await storageFolder.CreateFileAsync("xyz.txt",CreationCollisionOption.ReplaceExisting);

            //将字符串转换成二进制数据，并保存到指定文件
            string textContent = "helllollllllllllllll";
            InMemoryRandomAccessStream memoryStream = new InMemoryRandomAccessStream();
            DataWriter dataWriter = new DataWriter(memoryStream);
            dataWriter.WriteString(textContent);
            IBuffer buffer = dataWriter.DetachBuffer();
            await FileIO.WriteBufferAsync(storageFile,buffer);

            lblMsg.Text = "写入成功";
        }

        private async void btnReadBinary_Click(object sender, RoutedEventArgs e)
        {
            //在指定的目录下获取指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;
            try
            {
                StorageFile storageFile = await storageFolder.GetFileAsync("xyz.txt");
                if (storageFile != null)
                {
                    //获取指定文件中的二进制数据，将其转换成字符串并显示
                    IBuffer buffer = await FileIO.ReadBufferAsync(storageFile);
                    DataReader dataReader = DataReader.FromBuffer(buffer);
                    string textContent = dataReader.ReadString(buffer.Length);

                    lblMsg.Text = "读取结果：" + textContent;
                }
            }
            catch(Exception ex)
            {
                lblMsg.Text = "读取失败：" + ex;
            }

        }

    }
}

3、演示如何读写流数据

<StackPanel Margin="0 50">

            <Button Name="btnWrteStream" Content="Stream方式写入" Click="btnWrteStream_Click" Margin="5"></Button>
            <Button Name="btnReadStream" Content="Stream方式读取" Click="btnReadStream_Click" Margin="5"></Button>
            <TextBlock Name="lblMsg" Margin="5"></TextBlock>

        </StackPanel>

FileSystem/ReadWriteStream.xaml.cs

/*
 * 演示如何读写流数据
 * 注：如果需要读写某扩展名的文件，需要在 Package.appxmanifest 增加“文件类型关联”声明，并做相应的配置
 * 
 * StorageFolder - 文件夹操作类
 *     获取文件夹相关属性、重命名、Create...、Get...等
 * 
 * StorageFile - 文件操作类
 *     获取文件相关属性、重命名、Create...、Get...、Copy...、Move...、Delete...、Open...、Replace...等
 *     
 * IBuffer - WinRT 中的字节数组
 * 
 * IInputStream - 需要读取的流
 * IOutputStream - 需要写入的流
 * IRandomAccessStream - 需要读取、写入的流，其继承自 IInputStream 和 IOutputStream
 * 
 * DataReader - 从数据流中读取数据，即从 IInputStream 读取
 *     LoadAsync() - 从数据流中加载指定长度的数据到缓冲区
 *     ReadInt32(), ReadByte(), ReadString() 等 - 从缓冲区中读取数据
 * DataWriter - 将数据写入数据流，即写入 IOutputStream
 *     WriteInt32(), WriteByte(), WriteString() 等 - 将数据写入缓冲区
 *     StoreAsync() - 将缓冲区中的数据保存到数据流
 * 
 * StorageStreamTransaction - 用于写数据流到文件的类（具体用法，详见下面的代码）
 *     Stream - 数据流（只读）
 *     CommitAsync - 将数据流保存到文件
 *     
 * 注：WinRT 中的关于存储操作的相关类都在 Windows.Storage 命名空间内
 */

using System;
using Windows.Storage;
using Windows.Storage.Streams;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace XamlDemo.FileSystem
{
    public sealed partial class ReadWriteStream : Page
    {
        public ReadWriteStream()
        {
            this.InitializeComponent();
        }

 private async void btnWrteStream_Click(object sender, RoutedEventArgs e)
        {
            //在指定的目录下创建指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;
            StorageFile storageFile = await storageFolder.CreateFileAsync("stream.txt", CreationCollisionOption.ReplaceExisting);

            string textContent = "i am stream";
            StorageStreamTransaction transaction = await storageFile.OpenTransactedWriteAsync();
            DataWriter dataWriter = new DataWriter(transaction.Stream);
            //将字符串写入数据流，然后将数据流保存到文件
            dataWriter.WriteString(textContent);
            transaction.Stream.Size = await dataWriter.StoreAsync();
            await transaction.CommitAsync();

            lblMsg.Text = "写入成功";
        }

        private async void btnReadStream_Click(object sender, RoutedEventArgs e)
        {
            //在指定的目录下获取指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;
            try
            {
                StorageFile storageFile = await storageFolder.GetFileAsync("stream.txt");
                if (storageFile != null)
                {
                    IRandomAccessStream randomStream = await storageFile.OpenAsync(FileAccessMode.Read);
                    DataReader dataReader = new DataReader(randomStream);
                    ulong size = randomStream.Size;
                    if (size <= uint.MaxValue)
                    {
                        //获取数据流，从中读取字符串值并显示
                        uint numBytesLoaded = await dataReader.LoadAsync((uint)size);
                        string fileContent = dataReader.ReadString(numBytesLoaded);

                        lblMsg.Text = "读取结果：" + fileContent;
                    }
                }

            }
            catch(Exception ex)
            {
                lblMsg.Text = "读取文件失败：" +ex;
            }
       

        }
    }
}

4、演示如何读写“最近访问列表”和“未来访问列表”

<StackPanel Margin="0,50 ">

            <TextBlock Name="lblMsg" FontSize="14"></TextBlock>
            <Button Name="btnAddToMostRecentlyUseList" Content="AddToMostRecentlyUseList" Click="btnAddToMostRecentlyUseList_Click"  Margin="5"></Button>
            <Button Name="btnGetMostRecentlyUsedList" Content="GetMostRecentlyUsedList" Click="btnGetMostRecentlyUsedList_Click"  Margin="5"></Button>
            <Button Name="btnAddToFutureAccessLsit" Content="AddToFutureAccessList" Click="btnAddToFutureAccessLsit_Click" Margin="5"></Button>
            <Button Name="btnGetFutureAccessList" Content="GetFutureAccessList" Click="btnGetFutureAccessList_Click" Margin="5"></Button>
        </StackPanel>

FileSystem/CacheAccess.xaml.cs

/*
          * 演示如何读写“最近访问列表”和“未来访问列表”
          * 注：如果需要读写某扩展名的文件，需要在 Package.appxmanifest 增加“文件类型关联”声明，并做相应的配置
          *
          * StorageFolder - 文件夹操作类
          *     获取文件夹相关属性、重命名、Create...、Get...等
          *
          * StorageFile - 文件操作类
          *     获取文件相关属性、重命名、Create...、Get...、Copy...、Move...、Delete...、Open...、Replace...等
          *    
          * StorageApplicationPermissions - 文件/文件夹的访问列表
          *     MostRecentlyUsedList - 最近访问列表（实现了 IStorageItemAccessList 接口）
          *         Add(IStorageItem file, string metadata) - 添加文件或文件夹到“最近访问列表”，返回 token 值（一个字符串类型的标识），通过此值可以方便地检索到对应的文件或文件夹
          *             file - 需要添加到列表的文件或文件夹
          *             metadata - 自定义元数据，相当于上下文
          *         AddOrReplace(string token, IStorageItem file, string metadata) - 添加文件或文件夹到“最近访问列表”，如果已存在则替换
          *         GetFileAsync(string token) - 根据 token 值，在“最近访问列表”查找对应的文件
          *         GetFolderAsync(string token) - 根据 token 值，在“最近访问列表”查找对应的文件夹
          *         GetItemAsync(string token) - 根据 token 值，在“最近访问列表”查找对应的文件或文件夹
          *         Entries - 返回 AccessListEntryView 类型的数据，其是 AccessListEntry 类型数据的集合
          *     FutureAccessList - 未来访问列表（实现了 IStorageItemAccessList 接口）
          *         基本用法同“MostRecentlyUsedList”
          *        
          * AccessListEntry - 用于封装访问列表中的 StorageFile 或 StorageFolder 的 token 和元数据
          *     Token - token 值
          *     Metadata - 元数据
          *    
          * 注：WinRT 中的关于存储操作的相关类都在 Windows.Storage 命名空间内
          */

        protected async override void OnNavigatedTo(NavigationEventArgs e)
        {
            // 在指定的目录下创建指定的文件
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;// KnownFolders.DocumentsLibrary;
            StorageFile storageFile = await storageFolder.CreateFileAsync("webabcdCacheAccess.txt", CreationCollisionOption.ReplaceExisting);

            // 在指定的文件中写入指定的文本
            string textContent = "I am webabcd";
            await FileIO.WriteTextAsync(storageFile, textContent, Windows.Storage.Streams.UnicodeEncoding.Utf8);
        }

        private async void btnAddToMostRecentlyUseList_Click(object sender, RoutedEventArgs e)
        {
            // 获取文件对象
            StorageFolder storageFolder = KnownFolders.PicturesLibrary; // KnownFolders.DocumentsLibrary;
            StorageFile storageFile = await storageFolder.GetFileAsync("webabcdCacheAccess.txt");
            if(storageFile!=null)
            {
                //将文件添加到“最近访问列表”，并获取对应的token值
                string token = StorageApplicationPermissions.MostRecentlyUsedList.Add(storageFile, storageFile.Name);
                lblMsg.Text = "token:"+token;
            }
        }

        private async void btnGetMostRecentlyUsedList_Click(object sender, RoutedEventArgs e)
        {
            AccessListEntryView entries = StorageApplicationPermissions.MostRecentlyUsedList.Entries;
            if(entries.Count>0)
            {
                //通过token值，从 最近访问列表 中获取文件对象
                AccessListEntry entry = entries[0];
                StorageFile storageFile = await StorageApplicationPermissions.MostRecentlyUsedList.GetFileAsync(entry.Token);
                string textContent = await FileIO.ReadTextAsync(storageFile);
                lblMsg.Text = "MostRecentlyUsedList的第一个文件的文本内容：" + textContent;
            }
            else
            {
                lblMsg.Text = "最近访问列表中无数据";
            }
        }

        private async void btnAddToFutureAccessLsit_Click(object sender, RoutedEventArgs e)
        {
            // 获取文件对象
            StorageFolder storageFolder = KnownFolders.PicturesLibrary;// KnownFolders.DocumentsLibrary;
            StorageFile storageFile = await storageFolder.GetFileAsync("webabcdCacheAccess.txt");

            if (storageFile != null)
            {
                //将文件添加到“未来访问列表”，并获取对应的token值
                string token = StorageApplicationPermissions.FutureAccessList.Add(storageFile, storageFile.Name);
                lblMsg.Text = "token" + token;
            }
        }

        private async void btnGetFutureAccessList_Click(object sender, RoutedEventArgs e)
        {
            AccessListEntryView entries = StorageApplicationPermissions.FutureAccessList.Entries;
            if(entries.Count>0)
            {
                //通过token值，从 未来访问列表中获取文件对象
                AccessListEntry entry = entries[0];
                StorageFile storageFile=await StorageApplicationPermissions.FutureAccessList.GetFileAsync(entry.Token);
                string textContent = await FileIO.ReadTextAsync(storageFile);
                lblMsg.Text = "FutureAccessList的第一个文件的文本内容：" + textContent;
            }
            else
            {
                lblMsg.Text = "未来访问列表中无数据";
            }
        }
    }