在 WP 上使用 MvvmCross 拍摄图像并显示图像时出现问题

我想用相机拍照并将其显示在我所在的页面上

所以我有一个 ViewModel，我可以在其中拍照并显示它

public class CamViewModel : MvxViewModel,
    IMvxServiceConsumer<IInstalledMeter>,
    IMvxServiceConsumer<ICamaraService>        
{
    public CamViewModel()
    {
        this.GetService<ICamaraService>().PhotoSavedEvent += PhotoSaved;

        if (!String.IsNullOrEmpty(this.GetService<IInstalledMeter>().ImagePath))
        {
            ImagePath = this.GetService<IInstalledMeter>().ImagePath;
        }

        TakePicture();
    }

    private string _imagePath;
    public string ImagePath
    {
        get { return _imagePath; }
        set { _imagePath = value; FirePropertyChanged("ImagePath"); }
    }

    //Navigate back to InstallUnit
    public IMvxCommand OpenCamaraCommand
    {
        get
        {
            return new MvxRelayCommand(TakePicture);
        }
    }

    private void PhotoSaved(object sender, PhotoSavedResultEventArgs e)
    {
        ImagePath = e.ImagePath;
    }

    private void TakePicture()
    {
        this.GetService<ICamaraService>().TakePhoto();
    }
}

这使用了 CameraService 来拍摄照片并将照片保存在独立的存储中（我知道，问题分离不好）

public class CamaraService : IMvxServiceConsumer<IMvxPictureChooserTask>, IMvxServiceConsumer<IMvxSimpleFileStoreService>, IMvxServiceConsumer<IInstalledMeter>, ICamaraService
{
    private const int MaxPixelDimension = 1024;
    private const int DefaultJpegQuality = 70;

    public event EventHandler<PhotoSavedResultEventArgs> PhotoSavedEvent;
    private void PhotoTaken(PhotoSavedResultEventArgs e)
    {
        if (PhotoSavedEvent != null)
        {
            PhotoSavedEvent(this, e);
        }
    }

    public string ImagePath { get; set; }

    public void TakePicture()
    {
        this.GetService<IMvxPictureChooserTask>().TakePicture(
            MaxPixelDimension, 
            DefaultJpegQuality,
            SavePicture, 
            () => { /* cancel is ignored */ });
    }
    public void TakePhoto()
    {
        TakePicture();
    }

    public void SavePicture(Stream image)
    {
        var newImage = Save(image);
        if (newImage != "")
        {
            DeleteOldImage(this.GetService<IInstalledMeter>().ImagePath);
            this.GetService<IInstalledMeter>().ImagePath = newImage;
            PhotoTaken(new PhotoSavedResultEventArgs {ImagePath = newImage});
        }
    }

    public void UpdateModel(string filename)
    {

    }

    public void DeleteOldImage(string fileName)
    {
        try
        {
            if (String.IsNullOrEmpty(fileName)) return;
            var fileService = this.GetService<IMvxSimpleFileStoreService>();
            fileService.DeleteFile(fileName);
        }
        catch
        {
        }
    }

    public string Save(Stream stream)
    {
        try
        {
            var fileName = Guid.NewGuid().ToString();
            var fileService = this.GetService<IMvxSimpleFileStoreService>();
            fileName = Path.Combine("Image", fileName);
            fileService.WriteFile(fileName, stream.CopyTo);
            return fileName;
        }
        catch (ThreadAbortException)
        {
            throw;
        }
        catch (Exception exception)
        {
            return "";
        }
    }
}

Windows Phone 上显示图像的视图是

<Views:BaseCamView
x:Class="UI.WP7.Views.InstallMeter.CamView"
xmlns:Views="clr-namespace:UI.WP7.Views.InstallMeter"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:nativeConverters="clr-namespace:UI.WP7.NativeConverters"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
mc:Ignorable="d"
shell:SystemTray.IsVisible="True">

<Views:BaseCamView.Resources>
    <nativeConverters:PathToImageConverter x:Name="PathToImageConverter" />
</Views:BaseCamView.Resources>

<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <!--TitlePanel contains the name of the application and page title-->
    <StackPanel Grid.Row="0" Margin="12,17,0,28">
        <TextBlock Text="MY sdf" Style="{StaticResource PhoneTextNormalStyle}"/>
        <TextBlock Text="{Binding ImagePath}" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
    </StackPanel>

    <Image Grid.Row="1" Source="{Binding ImagePath, Converter={StaticResource PathToImageConverter}}"  Height="200" Width="700" Stretch="Uniform" />

</Grid>

这个视图使用转换器将路径转换为位图图像

public class PathToImageConverter : IValueConverter, IMvxServiceConsumer<IMvxSimpleFileStoreService>
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        byte[] contents = null;
        try
        {
            var file = this.GetService();
            file.TryReadBinaryFile((string)value, out contents);
        }
        catch (Exception)
        {
            // masked
        }

        if (contents == null)
            return null;

        using (var stream = new MemoryStream(contents))
        {
            var image = new BitmapImage();
            image.SetSource(stream);
            return image;
        }
    }

但是当我尝试拍照时，转换器中的这一点会返回 null

if (contents == null)
        return null;

所以我认为这意味着图像无法访问/保存或文件名错误，但不确定错误发生在哪里

我认为您需要单步执行并调试照片代码。

您还可以尝试向异常捕获处理程序添加一些跟踪。

一种猜测是您的基于 GUID 的文件名包含无效字符 - 请参阅http://msdn.microsoft.com/en-us/library/system.io.path.getinvalidpathchars%28v=vs.95%29.aspx http://msdn.microsoft.com/en-us/library/system.io.path.getinvalidpathchars%28v=vs.95%29.aspx Try Guid.ToString("N") + ".jpg"一个稍微不那么混乱的文件名

但实际上您需要跟踪代码并找出错误发生的位置。