背水一战 Windows 10 (89) - 文件系统: 读写文本数据, 读写二进制数据, 读写流数据

Posted 2020-11-18 webabcd

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背水一战 Windows 10 (89) - 文件系统: 读写文本数据, 读写二进制数据, 读写流数据

作者：webabcd


介绍
背水一战 Windows 10 之 文件系统

• 读写文本数据
• 读写二进制数据
• 读写流数据

示例
1、演示如何读写文本数据
FileSystem/ReadWriteText.xaml

<Page
    x:Class="Windows10.FileSystem.ReadWriteText"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Windows10.FileSystem"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="10 0 10 10">

            <TextBlock Name="lblMsg" Margin="5" />

            <Button Name="btnWriteText" Content="Write Text" Click="btnWriteText_Click" Margin="5" />

            <Button Name="btnReadText" Content="Read Text" Click="btnReadText_Click" Margin="5" />

        </StackPanel>
    </Grid>
</Page>

FileSystem/ReadWriteText.xaml.cs

/*
 * 演示如何读写文本数据
 *     
 * 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() - 将指定的多段文本数据写入到指定的文件
 *     AppendLinesAsync() - 将指定的多段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
 */

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

namespace Windows10.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 = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.CreateFileAsync("webabcdText.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); // 编码为 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 = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.GetFileAsync("webabcdText.txt");

            if (storageFile != null)
            {
                // 获取指定的文件中的文本内容
                string textContent = await FileIO.ReadTextAsync(storageFile, Windows.Storage.Streams.UnicodeEncoding.Utf8); // 编码为 UnicodeEncoding.Utf8
                lblMsg.Text = "读取结果：" + textContent;
            }
        }
    }
}

2、演示如何读写二进制数据
FileSystem/ReadWriteBinary.xaml

<Page
    x:Class="Windows10.FileSystem.ReadWriteBinary"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Windows10.FileSystem"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="10 0 10 10">

            <TextBlock Name="lblMsg" Margin="5" />

            <Button Name="btnWriteBinary" Content="Write Binary" Click="btnWriteBinary_Click" Margin="5" />

            <Button Name="btnReadBinary" Content="Read Binary" Click="btnReadBinary_Click" Margin="5" />

        </StackPanel>
    </Grid>
</Page>

FileSystem/ReadWriteBinary.xaml.cs

/*
 * 演示如何读写二进制数据
 * 
 * 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 - 字节数组
 */

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

namespace Windows10.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 = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.CreateFileAsync("webabcdBinary.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 = "I am webabcd";
            IBuffer buffer = ConverterHelper.String2Buffer(textContent);
            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 = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.GetFileAsync("webabcdBinary.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);
                string textContent = ConverterHelper.Buffer2String(buffer);

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

3、演示如何读写流数据
FileSystem/ReadWriteStream.xaml

<Page
    x:Class="Windows10.FileSystem.ReadWriteStream"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Windows10.FileSystem"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="Transparent">
        <StackPanel Margin="10 0 10 10">

            <TextBlock Name="lblMsg" Margin="5" />

            <Button Name="btnWriteStream1" Content="Write Stream（通过 IRandomAccessStream 写）" Click="btnWriteStream1_Click" Margin="5" />

            <Button Name="btnWriteStream2" Content="Write Stream（通过 StorageStreamTransaction 写）" Click="btnWriteStream2_Click" Margin="5" />

            <Button Name="btnReadStream" Content="Read Stream" Click="btnReadStream_Click" Margin="5" />

        </StackPanel>
    </Grid>
</Page>

FileSystem/ReadWriteStream.xaml.cs

/*
 * 演示如何读写流数据
 * 
 * IBuffer - 字节数组
 * 
 * IInputStream - 支持读取的流
 * IOutputStream - 支持写入的流
 * IRandomAccessStream - 支持读取和写入的流，其继承自 IInputStream 和 IOutputStream
 * 
 * DataReader - 数据读取器，用于从数据流中读取数据
 *     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 - 数据写入器，用于将数据写入数据流
 *     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（它写文件的方式是：先写临时文件，然后临时文件重命名）
 *     Stream - 数据流（只读）
 *     CommitAsync - 重命名临时文件   
 *     
 * StorageFile - 文件操作类
 *     public IAsyncOperation<IRandomAccessStream> OpenAsync(FileAccessMode accessMode) - 打开文件，返回 IRandomAccessStream 对象
 *     public IAsyncOperation<IRandomAccessStream> OpenAsync(FileAccessMode accessMode, StorageOpenOptions options) - 打开文件，返回 IRandomAccessStream 对象
 *         FileAccessMode.Read - 返回的流可读，不可写
 *         FileAccessMode.ReadWrite - 返回的流可读，可写
 *         StorageOpenOptions.AllowOnlyReaders - 其他调用者可读不可写
 *         StorageOpenOptions.AllowReadersAndWriters - 其他调用者可读可写
 *     public IAsyncOperation<StorageStreamTransaction> OpenTransactedWriteAsync() - 打开文件，返回 StorageStreamTransaction 对象
 *     public IAsyncOperation<StorageStreamTransaction> OpenTransactedWriteAsync(StorageOpenOptions options) - 打开文件，返回 StorageStreamTransaction 对象 
 */

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

namespace Windows10.FileSystem
{
    public sealed partial class ReadWriteStream : Page
    {
        public ReadWriteStream()
        {
            this.InitializeComponent();
        }

        // Write Stream（通过 IRandomAccessStream 写）
        private async void btnWriteStream1_Click(object sender, RoutedEventArgs e)
        {
            // 在指定的目录下创建指定的文件
            StorageFolder storageFolder = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.CreateFileAsync("webabcdStream.txt", CreationCollisionOption.ReplaceExisting);

            string textContent = "I am webabcd(IRandomAccessStream)";
            if (storageFile != null)
            {
                using (IRandomAccessStream randomStream = await storageFile.OpenAsync(FileAccessMode.ReadWrite))
                {
                    using (DataWriter dataWriter = new DataWriter(randomStream))
                    {
                        // 将字符串写入数据流
                        dataWriter.WriteString(textContent);

                        // 将数据流写入文件
                        await dataWriter.StoreAsync();

                        lblMsg.Text = "写入成功";
                    }
                }
            }
        }

        // Write Stream（通过 StorageStreamTransaction 写）
        private async void btnWriteStream2_Click(object sender, RoutedEventArgs e)
        {
            // 在指定的目录下创建指定的文件
            StorageFolder storageFolder = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.CreateFileAsync("webabcdStream.txt", CreationCollisionOption.ReplaceExisting);

            string textContent = "I am webabcd(StorageStreamTransaction)";

            using (StorageStreamTransaction transaction = await storageFile.OpenTransactedWriteAsync())
            {
                using (DataWriter dataWriter = new DataWriter(transaction.Stream))
                {
                    // 将字符串写入数据流
                    dataWriter.WriteString(textContent);

                    // 使用 StorageStreamTransaction 方式的话，调用 DataWriter 的 StoreAsync() 方法的作用是把数据写入临时文件
                    // 以本例为例，这个临时文件就是同目录下名为 webabcdStream.txt.~tmp 的文件。只要不调用 CommitAsync() 方法的话就会看到
                    // 返回值为写入数据的大小，需要通过此值更新 StorageStreamTransaction 中的 Stream 的大小
                    transaction.Stream.Size = await dataWriter.StoreAsync();

                    // 重命名临时文件
                    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 = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.DocumentsLibrary);
            StorageFile storageFile = await storageFolder.GetFileAsync("webabcdStream.txt");

            if (storageFile != null)
            {
                using (IRandomAccessStream randomStream = await storageFile.OpenAsync(FileAccessMode.Read))
                {
                    using (DataReader dataReader = new DataReader(randomStream))
                    {
                        ulong size = randomStream.Size;
                        if (size <= uint.MaxValue)
                        {
                            // 从数据流中读取数据
                            uint numBytesLoaded = await dataReader.LoadAsync((uint)size);

                            // 将读取到的数据转换为字符串
                            string fileContent = dataReader.ReadString(numBytesLoaded);

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

OK
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