在Windows Universal中将文件写入外部闪存驱动器 [英] Writing files to external flash drive in Windows Universal

问题描述

我正在Raspberry PI上使用Windows IoT编写应用程序.我想将数据写入连接到USB端口之一的外部闪存驱动器.我已经找到了有关如何在PI中写入SD卡的示例，但是在最终产品中将无法访问SD卡.

I'm writing an application using Windows IoT on a Raspberry PI. I would like to write data to an external flash drive connected to one of the USB ports. I've found examples on how to write to the SD card in the PI, but the SD card won't be accessible in the final product.

我可以获取闪存驱动器的根文件夹名称，但是当我尝试向其中写入文件时，会收到访问被拒绝的消息.如果我切换到SD卡，则一切正常.

I can get the root folder name of the flash drive, but when I try to write a file to it, I get an access denied message. If I switch to the SD card everything works fine.

有人可以指出允许访问外部闪存驱动器的示例吗?

Can anyone point me to an example that allows access to an external flash drive?

推荐答案

出于安全原因，通用Windows应用程序只能访问外部驱动器上的某些类型的文件，

For security reasons, Universal Windows Applications can only have access to certain types of files on external drives,

• 音乐
• 图片
• 视频

并且您必须在Package.appxmanifest文件中明确声明它.

And you have to explicitly declare it in the Package.appxmanifest file.

• 音乐图书馆
• 图片库
• 视频库

您可能还需要检查可移动存储功能.

You might also want to check the Removable Storage capability as well.

除上述三种类型外，我认为您无法访问常规文件格式，否则会出现访问被拒绝"异常.

I don't think you have access to a general file format except the above three types, otherwise you'll get an "Access is denied" exception.

在此处.

一旦声明了功能，就可以使用以下代码获取外部存储设备的根文件夹，

Once you have your capabilities declared, you can get the root folder for your external storage device with the following code,

var removableDevices = KnownFolders.RemovableDevices;
var externalDrives = await removableDevices.GetFoldersAsync();
var drive0 = externalDrives[0];

然后，您可以按照如果要将数据写入通用文件格式，一种解决方法是使用可访问的文件格式(例如jpg)，然后将原始数据写入其中.以下是一些代码示例，这些示例已在Raspberry Pi 2 Model B(带有Windows IoT 14393)以及连接到USB端口的外部USB驱动器上进行了验证.

If you want to write data to an generic file format, an workaround is to use an accessible file format(like jpg), and write your raw data to it. Below is some code sample that is verified on Raspberry Pi 2 Model B, with Windows IoT 14393, with an external USB drive connected to the USB port.

    private async void WriteData()
    {
        var removableDevices = KnownFolders.RemovableDevices;
        var externalDrives = await removableDevices.GetFoldersAsync();
        var drive0 = externalDrives[0];

        var testFolder = await drive0.CreateFolderAsync("Test");
        var testFile = await testFolder.CreateFileAsync("Test.jpg");

        var byteArray = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
        using (var sourceStream = new MemoryStream(byteArray).AsRandomAccessStream())
        {
            using (var destinationStream = (await testFile.OpenAsync(FileAccessMode.ReadWrite)).GetOutputStreamAt(0))
            {
                await RandomAccessStream.CopyAndCloseAsync(sourceStream, destinationStream);
            }
        }
    }

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