如何到达我的视图模型上的mediaFile并在其内容页面上使用它?

问题描述

我正在尝试从选择图片时获取基础图像数据.该功能本身带有摄像头和选择图片的功能非常完美，我只缺少一件事，那就是获取图像数据.我假设imagedata位于返回的mediaFile中，但是我不确定如何在contentPage上到达它.

I am trying to get the underlying image data from when you select a picture. The function itself with the cameraalbum and selecting a picture works perfectly and I am only missing one thing and that is to get the image data. The imagedata is inside the returned mediaFile i assume but I am not sure how I can reach it on my contentPage.

(我使用这个项目: https://github.com/XLabs/Xamarin-Forms-Labs/wiki/Camera )

想法是将图像数据发送到内容页面上的我的数据库中.

The idea is to send the imagedata to my database on the contentpage.

这是名为"CameraViewModel"的视图模型:

This is the viewmodel named "CameraViewModel":

public async Task SelectPicture()
    {
        Setup ();

        ImageSource = null;

        try
        {
            var mediaFile = await _Mediapicker.SelectPhotoAsync(new CameraMediaStorageOptions
                {
                    DefaultCamera = CameraDevice.Front,
                    MaxPixelDimension = 400
                });

            VideoInfo = mediaFile.Path;
            ImageSource = ImageSource.FromStream(() => mediaFile.Source);


        }
        catch (System.Exception ex)
        {
            Status = ex.Message;

        }
    }

现在在我的内容页面上，我有这个:

On my contentpage right now I have this:

CameraViewModel cameraOps = null;

    public PhotoPage ()
    {
        InitializeComponent ();

        cameraOps = new CameraViewModel ();
        cameraOps. //trying to reach the mediafile here
    }

更新的代码:

private MediaFile _file;
    public MediaFile File
    {
        get { return _file; }
        set
        {
            _file = value;
        }
    }

public async Task SelectPicture()
    {
        Setup ();

        ImageSource = null;

        try
        {
            File = await _Mediapicker.SelectPhotoAsync(new CameraMediaStorageOptions
                {
                    DefaultCamera = CameraDevice.Front,
                    MaxPixelDimension = 400
                });

            VideoInfo = File.Path;
            ImageSource = ImageSource.FromStream(() => File.Source);


        }
        catch (System.Exception ex)
        {
            Status = ex.Message;

        }
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {

        File = value as MediaFile;
        return ImageSource.FromStream(() => File.Source);
    }

推荐答案

您可以在视图模型上创建属性:

You could create property on view model:

    private MediaFile _file;
    public MediaFile File
    {
        get { return _file; }
        set
        {
            _file = value;
            OnPropertyChanged();
        }
    }

然后将其绑定到ContentPage:

<Image Source="{Binding File}, Converter={StaticResource MediaFileToImageSourceConverter}">

转换器:

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
         var file = value as MediaFile;
         return ImageSource.FromStream(() => file.GetStream()));
    }

更新的代码:(不是mvvm的最佳传统，而是为您提供的示例)

Updated code: (not in best traditions of mvvm, but for your sample)

    public async Task<MediaFile> SelectPicture()
    {
        Setup();

        MediaFile file = null;

        try
        {
            file = await _Mediapicker.SelectPhotoAsync(new CameraMediaStorageOptions
            {
                DefaultCamera = CameraDevice.Front,
                MaxPixelDimension = 400
            });

        }
        catch (System.Exception ex)
        {
            Status = ex.Message;
        }

        return file;
    }

关于后面的代码:

    public async void OnTakePhotoButtonClicked(object sender, EventArgs args)
    {
        var file = await cameraOps.SelectPicture();
        someImage.ImageSource = ImageSource.FromStream(() => file.Source);
    }

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