获取文件的缩略图Thumbnail和通过 AQS

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);
        }
    }
}