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重新想象 Windows 8 Store Apps (22) 文件系统: 访问文件夹和文件, 通过 AQS 搜索本地文件

重新想象 Windows 8 Store Apps (22) - 文件系统: 访问文件夹和文件, 通过 AQS 搜索本地文件

作者：webabcd

介绍
重新想象 Windows 8 Store Apps 之文件系统

File Access - 访问文件夹和文件，以及获取文件的各种属性
Folder Access - 遍历文件夹时的一些特殊操作
Thumbnail Access - 获取文件的缩略图
AQS - 通过 AQS（Advanced Query Syntax）搜索本地文件

示例
1、演示如何访问文件夹和文件，以及如何获取文件的各种属性
FileSystem/FileAccess.xaml

<Page
    x:Class="XamlDemo.FileSystem.FileAccess"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.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="120 0 0 0">

            <TextBlock Name="lblMsg" FontSize="14.667" />
         
            <ListBox Name="listBox" Width="400" Height="200" SelectionChanged="listBox_SelectionChanged_1" HorizontalAlignment="Left" Margin="0 10 0 0" />
            
        </StackPanel>
    </Grid>
</Page>

FileSystem/FileAccess.xaml.cs

/*
 * 演示如何访问文件夹和文件，以及如何获取文件的各种属性
 * 
 * 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
 *     
 * 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 System.Collections.Generic;
using Windows.Storage;
using Windows.Storage.FileProperties;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;
using System.Linq;

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

        protected async override void OnNavigatedTo(NavigationEventArgs e)
        {
            // 遍历“文档库”目录下的所有顶级文件（需要在 Package.appxmanifest 中选中“文档库”功能）
            StorageFolder storageFolder = KnownFolders.DocumentsLibrary;
            IReadOnlyList<StorageFile> files = await storageFolder.GetFilesAsync();
            listBox.ItemsSource = files.Select(p => p.Name).ToList();
        }

        private async void listBox_SelectionChanged_1(object sender, SelectionChangedEventArgs e)
        {
            // 获取用户选中的文件
            string fileName = (string)listBox.SelectedItem;
            StorageFolder storageFolder = KnownFolders.DocumentsLibrary;
            StorageFile storageFile = await storageFolder.GetFileAsync(fileName);

            // 显示文件的各种属性
            if (storageFile != null)
            {
                lblMsg.Text = "Name：" + storageFile.Name;
                lblMsg.Text += Environment.NewLine;
                lblMsg.Text += "FileType：" + storageFile.FileType;
                lblMsg.Text += Environment.NewLine;

                BasicProperties basicProperties = await storageFile.GetBasicPropertiesAsync();
                lblMsg.Text += "Size：" + basicProperties.Size;
                lblMsg.Text += Environment.NewLine;
                lblMsg.Text += "DateModified：" + basicProperties.DateModified;
                lblMsg.Text += Environment.NewLine;

                /*
                 * 获取文件的其它各种属性
                 * 详细属性列表请参见：http://msdn.microsoft.com/en-us/library/windows/desktop/ff521735(v=vs.85).aspx
                 */
                List<string> propertiesName = new List<string>();
                propertiesName.Add("System.DateAccessed");
                propertiesName.Add("System.DateCreated");
                propertiesName.Add("System.FileOwner");
                IDictionary<string, object> extraProperties = await storageFile.Properties.RetrievePropertiesAsync(propertiesName);

                lblMsg.Text += "System.DateAccessed：" + extraProperties["System.DateAccessed"];
                lblMsg.Text += Environment.NewLine;
                lblMsg.Text += "System.DateCreated：" + extraProperties["System.DateCreated"];
                lblMsg.Text += Environment.NewLine;
                lblMsg.Text += "System.FileOwner：" + extraProperties["System.FileOwner"];
            }
        }
    }
}

2、演示遍历文件夹时的一些特殊操作
FileSystem/FolderAccess.xaml

<Page
    x:Class="XamlDemo.FileSystem.FolderAccess"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.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="120 0 0 0">

            <TextBlock Name="lblMsg" FontSize="14.667" />

            <Button Name="btnGroupFile" Content="分组文件" Click="btnGroupFile_Click_1" Margin="0 10 0 0" />

            <Button Name="btnPrefetchAPI" Content="从 Prefetch 中加载信息" Click="btnPrefetchAPI_Click_1" Margin="0 10 0 0" />
            
        </StackPanel>
    </Grid>
</Page>

FileSystem/FolderAccess.xaml.cs

/*
 * 演示遍历文件夹时的一些特殊操作
 * 1、演示如何对 StorageFolder 中的内容做分组
 * 2、演示如何通过文件扩展名过滤内容，以及如何从 Prefetch 中获取数据
 * 
 * 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
 *     
 * 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 System.Collections.Generic;
using Windows.Storage;
using Windows.Storage.FileProperties;
using Windows.Storage.Search;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

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

        // 演示如何对 StorageFolder 中的内容做分组
        private async void btnGroupFile_Click_1(object sender, Windows.UI.Xaml.RoutedEventArgs e)
        {
            lblMsg.Text = "";

            StorageFolder picturesFolder = KnownFolders.PicturesLibrary;

            // 创建一个按月份分组的查询
            QueryOptions queryOptions = new QueryOptions(CommonFolderQuery.GroupByMonth);
            // 对指定文件夹执行指定的文件夹查询，返回分组后的文件夹数据
            StorageFolderQueryResult queryResult = picturesFolder.CreateFolderQueryWithOptions(queryOptions);

            IReadOnlyList<StorageFolder> folderList = await queryResult.GetFoldersAsync();
            foreach (StorageFolder folder in folderList) // 这里的 floder 就是按月份分组后的月份文件夹（当然，物理上并没有月份文件夹）
            {
                IReadOnlyList<StorageFile> fileList = await folder.GetFilesAsync();
                lblMsg.Text += folder.Name + " (" + fileList.Count + ")";
                lblMsg.Text += Environment.NewLine;
                foreach (StorageFile file in fileList) // 月份文件夹内的文件
                {
                    lblMsg.Text += "    " + file.Name;
                    lblMsg.Text += Environment.NewLine;
                }
            }
        }

        // 演示如何通过文件扩展名过滤内容，以及如何从 Prefetch 中获取数据
        private async void btnPrefetchAPI_Click_1(object sender, Windows.UI.Xaml.RoutedEventArgs e)
        {
            /*
             * Prefetch 是预读的文件信息，其在 C:\Windows\Prefetch 目录内，可以从中获取文件属性信息和文件缩略图，在访问大量文件的场景下可以提高效率
             */

            lblMsg.Text = "";

            List<string> fileTypeFilter = new List<string>();
            fileTypeFilter.Add(".jpg");
            fileTypeFilter.Add(".png");

            // 新建一个查询，指定需要查询的文件的扩展名
            QueryOptions queryOptions = new QueryOptions(CommonFileQuery.OrderByName, fileTypeFilter);

            // 通过 QueryOptions.SetPropertyPrefetch() 来设置需要从 Prefetch 中获取的属性信息
            List<string> propertyNames = new List<string>();
            propertyNames.Add("System.FileOwner");
            queryOptions.SetPropertyPrefetch(PropertyPrefetchOptions.ImageProperties, propertyNames);

            /*
             * 通过 QueryOptions.SetThumbnailPrefetch() 来设置需要从 Prefetch 中获取的缩略图
               uint requestedSize = 190;
               ThumbnailMode thumbnailMode = ThumbnailMode.PicturesView;
               ThumbnailOptions thumbnailOptions = ThumbnailOptions.UseCurrentScale;
               queryOptions.SetThumbnailPrefetch(thumbnailMode, requestedSize, thumbnailOptions);
            */

            // 对指定文件夹执行指定的文件查询，返回查询后的文件数据
            StorageFileQueryResult queryResult = KnownFolders.PicturesLibrary.CreateFileQueryWithOptions(queryOptions);

            IReadOnlyList<StorageFile> fileList = await queryResult.GetFilesAsync();
            foreach (StorageFile file in fileList)
            {
                lblMsg.Text += file.Name; // 文件名

                // 获取图像属性
                ImageProperties properties = await file.Properties.GetImagePropertiesAsync(); 
                lblMsg.Text += "(" + properties.Width + "x" + properties.Height + ")";

                // 获取其他属性（详细属性列表请参见：http://msdn.microsoft.com/en-us/library/windows/desktop/ff521735(v=vs.85).aspx）
                IDictionary<string, object> extraProperties = await file.Properties.RetrievePropertiesAsync(propertyNames);
                lblMsg.Text += "(" + extraProperties["System.FileOwner"] + ")";
                
                // 获取缩略图
                // StorageItemThumbnail thumbnail = await file.GetThumbnailAsync(thumbnailMode, requestedSize, thumbnailOptions);
            }
        }
    }
}

3、演示如何获取文件的缩略图
FileSystem/ThumbnailAccess.xaml

<Page
    x:Class="XamlDemo.FileSystem.ThumbnailAccess"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:XamlDemo.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">
       <ScrollViewer Margin="120 0 0 0">
            <StackPanel>

                <Button Name="btnGetThumbnail" Content="获取文件的缩略图" Click="btnGetThumbnail_Click_1" />

                <Image Name="img" Stretch="None" HorizontalAlignment="Left" Margin="0 10 0 0" />
                <TextBlock Name="lblMsg" FontSize="14.667" Margin="0 10 0 0" />

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

FileSystem/ThumbnailAccess.xaml.cs

/*
 * 演示如何获取文件的缩略图
 * 
 * 获取指定文件或文件夹的缩略图，返回 StorageItemThumbnail 类型的数据
 * StorageFile.GetThumbnailAsync(ThumbnailMode mode, uint requestedSize, ThumbnailOptions options)
 * StorageFolder.GetThumbnailAsync(ThumbnailMode mode, uint requestedSize, ThumbnailOptions options)
 *     ThumbnailMode mode - 用于描述缩略图的目的，以使系统确定缩略图图像的调整方式（PicturesView, VideosView, MusicView, DocumentsView, ListView, SingleItem）
 *         关于 ThumbnailMode 的详细介绍参见：http://msdn.microsoft.com/en-us/library/windows/apps/hh465350.aspx
 *     uint requestedSize - 期望尺寸的最长边长的大小
 *     ThumbnailOptions options - 检索和调整缩略图的行为（None, ReturnOnlyIfCached, ResizeThumbnail, UseCurrentScale）
 */

using System;
using Windows.Storage;
using Windows.Storage.FileProperties;
using Windows.Storage.Pickers;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media.Imaging;

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

        private async void btnGetThumbnail_Click_1(object sender, RoutedEventArgs e)
        {
            if (XamlDemo.Common.Helper.EnsureUnsnapped())
            {
                FileOpenPicker openPicker = new FileOpenPicker();
                openPicker.FileTypeFilter.Add("*");

                StorageFile file = await openPicker.PickSingleFileAsync();
                if (file != null)
                {   
                    ThumbnailMode thumbnailMode = ThumbnailMode.PicturesView;
                    ThumbnailOptions thumbnailOptions = ThumbnailOptions.UseCurrentScale;
                    uint requestedSize = 200;

                    using (StorageItemThumbnail thumbnail = await file.GetThumbnailAsync(thumbnailMode, requestedSize, thumbnailOptions)) 
                    {
                        if (thumbnail != null)
                        {
                            BitmapImage bitmapImage = new BitmapImage();
                            bitmapImage.SetSource(thumbnail);
                            img.Source = bitmapImage;

                            lblMsg.Text = "file name: " + file.Name;
                            lblMsg.Text += Environment.NewLine;
                            lblMsg.Text += "requested size: " + requestedSize;
                            lblMsg.Text += Environment.NewLine;
                            lblMsg.Text += "returned size: " + thumbnail.OriginalWidth + "*" + thumbnail.OriginalHeight;
                        }
                    }
                }
            }
        }
    }
}

4、演示如何通过 AQS - Advanced Query Syntax 搜索本地文件
FileSystem/AQS.xaml.cs

/*
 * 演示如何通过 AQS - Advanced Query Syntax 搜索本地文件
 */

using System;
using System.Collections.Generic;
using Windows.Storage;
using Windows.Storage.BulkAccess;
using Windows.Storage.FileProperties;
using Windows.Storage.Search;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

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

        protected async override void OnNavigatedTo(NavigationEventArgs e)
        {
            // 准备在“音乐库”中进行搜索（需要在 Package.appxmanifest 的“功能”中选中“音乐库”）
            StorageFolder musicFolder = KnownFolders.MusicLibrary;

            // 准备搜索所有类型的文件
            List<string> fileTypeFilter = new List<string>();
            fileTypeFilter.Add("*");

            // 搜索的查询参数
            QueryOptions queryOptions = new QueryOptions(CommonFileQuery.OrderByDate, fileTypeFilter);
            // 指定 AQS 字符串，参见 http://msdn.microsoft.com/zh-cn/library/windows/apps/aa965711.aspx
            queryOptions.UserSearchFilter = "五月天";

            // 根据指定的参数创建一个查询
            StorageFileQueryResult fileQuery = musicFolder.CreateFileQueryWithOptions(queryOptions);

            lblMsg.Text = "在音乐库中搜索“五月天”，结果如下：";
            lblMsg.Text += Environment.NewLine;

            // 开始搜索，并返回检索到的文件列表
            IReadOnlyList<StorageFile> files = await fileQuery.GetFilesAsync();

            if (files.Count == 0)
            {
                lblMsg.Text += "什么都没搜到";
            }
            else
            {
                foreach (StorageFile file in files)
                {
                    lblMsg.Text += file.Name;
                    lblMsg.Text += Environment.NewLine;
                }
            }



            // 关于 QueryOptions 的一些用法，更详细的 QueryOptions 的说明请参见 msdn
            queryOptions = new QueryOptions();
            queryOptions.FolderDepth = FolderDepth.Deep;
            queryOptions.IndexerOption = IndexerOption.UseIndexerWhenAvailable;
            queryOptions.SortOrder.Clear();
            var sortEntry = new SortEntry();
            sortEntry.PropertyName = "System.FileName";
            sortEntry.AscendingOrder = true;
            queryOptions.SortOrder.Add(sortEntry);

            fileQuery = KnownFolders.PicturesLibrary.CreateFileQueryWithOptions(queryOptions);
        }
    }
}

OK
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原文地址：https://www.cnblogs.com/webabcd/p/3041569.html