将IRandomAccessStreamWithContentType转换为Byte []

Question

在我的应用程序中,我允许用户使用ContactPicker从联系人中添加人员.

我尝试将IRandomAccessStreamWithContentType转换为Byte []

IRandomAccessStreamWithContentType stream = await contactInformation.GetThumbnailAsync();
if (stream != null && stream.Size > 0)
{
    Byte[] bytes = new Byte[stream.Size];
    await stream.ReadAsync(bytes.AsBuffer(), (uint)stream.Size, Windows.Storage.Streams.InputStreamOptions.None);

我的字节[]不为空(约10000字节)

但是当我使用Converter Byte []到ImageSource时,BitmapImage的宽度和高度为0.

我将这个转换器用于另一个应用程序,它工作得很好......

public object Convert(object value, Type targetType, object parameter, string language)
{
    try
    {
        Byte[] bytes = (Byte[])value;
        if (bytes == null)
           return (new BitmapImage(new Uri((String)parameter)));
        BitmapImage bitmapImage = new BitmapImage();
        IRandomAccessStream stream = this.ConvertToRandomAccessStream(new MemoryStream(bytes));
        bitmapImage.SetSource(stream);
        return (bitmapImage);
    }
    catch
    {
       return (new BitmapImage(new Uri((String)parameter)));
    }

}
private IRandomAccessStream ConvertToRandomAccessStream(MemoryStream memoryStream)
{
    var randomAccessStream = new InMemoryRandomAccessStream();
    var outputStream = randomAccessStream.GetOutputStreamAt(0);
    outputStream.AsStreamForWrite().Write(memoryStream.ToArray(), 0, (Int32)memoryStream.Length);

    return randomAccessStream;
}

如果有人知道问题是什么......

提前致谢.NeoKript

编辑:我已经将我的转换器用于另一个项目,它运行良好.主要区别在于流具有不同的原点:

var reader = await file.OpenReadAsync();
using (DataReader dataReader = new DataReader(reader))
{
    var bytes = new byte[reader.Size];
    await dataReader.LoadAsync((uint)reader.Size);
    dataReader.ReadBytes(bytes);
    // Use of bytes
}

Answer 1

我很确定bytes在你的情况下只包含零.你应该修改你的阅读代码:

var buffer = await stream.ReadAsync(bytes.AsBuffer(), (uint)stream.Size, InputStreamOptions.None);
bytes = buffer.ToArray();

或者甚至更好,完全避免IBuffer:

await stream.AsStream().ReadAsync(bytes, 0, bytes.Length);

在这两种情况下,字节数组现在都包含实际值.我仍然无法让你的转换器工作,我现在没有时间进一步排除故障.也许其他人会帮助你.

编辑:

我不确定你是否在另一个项目中使用转换器,但是如果不使用异步方法就无法在内部使用转换器IValueConverter.更改后ConvertToRandomAccessStream,位图按预期创建,没有任何其他修改(除了必需的await):

private async Task<IRandomAccessStream> ConvertToRandomAccessStream(byte[] bytes)
{
    var randomAccessStream = new InMemoryRandomAccessStream();
    using (var writer = new DataWriter(randomAccessStream))
    {
        writer.WriteBytes(bytes);
        await writer.StoreAsync();
        await writer.FlushAsync();
        writer.DetachStream();
    }
    randomAccessStream.Seek(0);

    return randomAccessStream;
}

我没有使用转换器,而是在视图模型中添加了一个返回位图的属性.在bytes属性中,我调用了用于创建位图的异步方法:

public Byte[] ImageBytes
{
    get { return _imageBytes; }
    set
    {
        if (Equals(value, _imageBytes)) return;
        _imageBytes = value;
        OnPropertyChanged();
        CreateBitmap();
    }
}

public BitmapSource Image
{
    get { return _image; }
    set
    {
        if (Equals(value, _image)) return;
        _image = value;
        OnPropertyChanged();
    }
}

private async Task CreateBitmap()
{
    try
    {
        BitmapImage bitmapImage = new BitmapImage();
        IRandomAccessStream stream = await this.ConvertToRandomAccessStream(ImageBytes);
        bitmapImage.SetSource(stream);
        Image = bitmapImage;
    }
    catch
    {
        Image = null;
    }
}