uwp选取文件夹并读取其中的图片

　　uwp对文件的操作和wpf,winform等等有很大的不同，主要原因是uwp对权限的要求比较严格，不能想从前那样随心所欲的读取文件。

　　1.首先找到Package.appxmanifest这个文件，在功能里面勾选需要的功能，在申明里添加，在此之后才能安心写代码。

 

　　2.打开文件选择器，选择文件夹，并保存选择的文件夹。

            //打开文件选择器
            FolderPicker pick = new FolderPicker();
            pick.FileTypeFilter.Add(".png");
            pick.FileTypeFilter.Add(".jpg");
            pick.FileTypeFilter.Add(".bmp");
            IAsyncOperation<StorageFolder> folderTask = pick.PickSingleFolderAsync();

            StorageFolder folder = await folderTask;

            //var folder = await pick.PickSingleFolderAsync();
            StorageFolder Folder = null;
            string Address;
            string Token = "";
            if (folder != null)
            {
                Folder = folder;
                Address = folder.Path;
                Token = StorageApplicationPermissions.FutureAccessList.Add(folder);
            }
            StorageApplicationPermissions.FutureAccessList.GetFolderAsync(Token);

            //获取本地文件夹
            StorageFolder folderLocal = ApplicationData.Current.LocalFolder;

            //创建一个文件夹account
            try
            {
                folderLocal = await folderLocal.GetFolderAsync(folderStr);
            }
            catch (FileNotFoundException)
            {
                folderLocal = await folderLocal.CreateFolderAsync(folderStr);
            }

            StorageFile file = await folderLocal.CreateFileAsync(
folderStr + ".json", CreationCollisionOption.ReplaceExisting);
            
            //保存选择的文件夹Token
            var json = JsonSerializer.Create();
            ImagePath imagePath = new ImagePath { Id = DateTime.Now.ToString("yyMMddHHmmss"), Path = Token };
            string imageJson = imagePath.Stringify();
            if (file != null)
            {
                try
                {
                    using (StorageStreamTransaction transaction = await file.OpenTransactedWriteAsync())
                    {
                        using (DataWriter dataWriter = new DataWriter(transaction.Stream))
                        {
                            dataWriter.WriteInt32(Encoding.UTF8.GetByteCount(imageJson));
                            dataWriter.WriteString(imageJson);
                            transaction.Stream.Size = await dataWriter.StoreAsync();
                            await transaction.CommitAsync();
                        }
                    }
                }
                catch (Exception ex)
                {
                    throw ex;
                }
            }            

　　3.获取已选择文件夹下的图片

            StorageFile fileLocal = await StorageFile.GetFileFromApplicationUriAsync(new Uri("ms-appdata:///local/account/" + ImageHelper.folderStr + ".json"));
            if (fileLocal != null)
            {
                try
                {
                    //读取本地文件内容，并且反序列化
                    using (IRandomAccessStream readStream = await fileLocal.OpenAsync(FileAccessMode.Read))
                    {
                        using (DataReader dataReader = new DataReader(readStream))
                        {
                            UInt64 size = readStream.Size;
                            if (size <= UInt32.MaxValue)
                            {
                                await dataReader.LoadAsync(sizeof(Int32));
                                Int32 stringSize = dataReader.ReadInt32();
                                await dataReader.LoadAsync((UInt32)stringSize);
                                string fileContent = dataReader.ReadString((uint)stringSize);
                                ImagePath imagePath = new ImagePath(fileContent);
                                StorageFolder folder = await StorageApplicationPermissions.FutureAccessList.GetFolderAsync(imagePath.Path);
                                //筛选图片
                                var queryOptions = new Windows.Storage.Search.QueryOptions();
                                queryOptions.FileTypeFilter.Add(".png");
                                queryOptions.FileTypeFilter.Add(".jpg");
                                queryOptions.FileTypeFilter.Add(".bmp");
                                var query = folder.CreateFileQueryWithOptions(queryOptions);
                                var files = await query.GetFilesAsync();

                                ImagePath img;
                                imgList = new ObservableCollection<ImagePath>();
                                foreach (var item in files)
                                {
                                    IRandomAccessStream irandom = await item.OpenAsync(FileAccessMode.Read);
                                   
                                    //对图像源使用流源
                                    BitmapImage bitmapImage = new BitmapImage();
                                    bitmapImage.DecodePixelWidth = 160;
                                    bitmapImage.DecodePixelHeight = 100;
                                    await bitmapImage.SetSourceAsync(irandom);

                                    img = new ImagePath();
                                    img.Path = item.Path;
                                    img.File = bitmapImage;
                                    img.Storage = item;
                                    imgList.Add(img);
                                }
                                
                                imageView.ItemsSource = imgList;
                            }

                        }
                    }
                }
                catch (Exception exce)
                {
                    await new MessageDialog(exce.ToString()).ShowAsync();
                    throw exce;
                }
            }

　　最后的实现显现效果大概如下：

　　

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谢谢yinyue200 的提醒，Package.appxmanifest可以不用配置。