Xamarin 使用 Media.Plugin 形成 MVVM (Prism) - 如何从设备存储中获取拍摄的照片 [英] Xamarin Forms MVVM (Prism) with Media.Plugin - How to get a taken picture from device storage

问题描述

我正在使用 Xamarin Forms PCL (MVVM Prism) 和 MediaPlugin (https://github.com/jamesmontemagno/MediaPlugin).

我有一个名为 ImagePath 的公共属性的 viewModel

I have a viewModel with a public property called ImagePath

private string imagePath;
public string ImagePath
{
   get { return imagePath; }
   set { SetProperty(ref imagePath, value, "ImagePath"); }
}

在我的 XAML 中，我有:

in my XAML i have:

<Image Source="{Binding ImagePath}" HeightRequest="100" WidthRequest="100"/>

当我将图像 url(来自 Web)设置为 ImagePath 属性时，它可以正常工作.(我正在设置这样的字符串:http://www.myaddress.com/myimage.jpg")

When i set a image url (from web) to ImagePath property, it works without problems. (I am setting an string like this: "http://www.myaddress.com/myimage.jpg")

但是，当我使用以下代码(MediaPlugin)拍照时:

But, when I take a picture using the following code (MediaPlugin):

var file = await CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions
            {
                Directory = "Sample",
                Name = "test.jpg"
            });

ImagePath = file.Path;

// also tried: ImagePath = ImageSource.FromFile(file.Path).toString();

var file.Path 接收这样的值:

the var file.Path receives a value like this:

"/storage/emulated/0/Android/data/{APPNAME}.Android/files/Pictures/{DIRECTORYNAME}/{IMAGENAME}"

"/storage/emulated/0/Android/data/{APPNAME}.Android/files/Pictures/{DIRECTORYNAME}/{IMAGENAME}"

使用这个 file.Path 值然后我设置 ImagePath 属性:ImagePath = file.Path;

With this file.Path value then i'm setting ImagePath property: ImagePath = file.Path;

但是拍摄的图像没有出现在屏幕上.

But the taken image does not appear on the screen.

我也曾尝试使用MediaPlugin 文档中建议的 Image.Source 属性，但是我还没有达到我想要的结果.

I also have tried to use the Image.Source property as suggested in MediaPlugin docs, however i have not reached the result i want.

我也尝试了以下方法:

公共属性进入虚拟机:

private Image image = new Image();
        public Image Image
        {
            get { return image; }
            set { SetProperty(ref image, value, "Image"); }
        }

XML:

<Image Source="{Binding Image.Source}" HeightRequest="100" WidthRequest="100"/>

设置文件值后(如前所示):

After set file value (as showed before):

image.Source = ImageSource.FromStream(() =>
                    {
                        var stream = file.GetStream();
                        file.Dispose();
                        return stream;
                    });

有什么办法让它工作吗?谢谢！！

Is there any way to make it work? Thanks!!

推荐答案

媒体插件返回一个 MediaFile.

The Media Plugin returns a MediaFile.

我将它存储在一个用于存储和显示的类中

I store this in a class I use for storage and display

public class IncidentImage
{
    [PrimaryKey, AutoIncrement]
    public int Id { get; set; }

    public int IncidentDetailsId { get; set; }

    public byte[] ImageBytes { get; set; }

    [Ignore]
    public ImageSource ImageSource
    {
        get
        {
            ImageSource retval = null;
            if (ImageBytes != null)
            {
                retval = ImageSource.FromStream(() => new MemoryStream(ImageBytes));
            }
            return retval;
        }
    }
}

像这样

    var incidentImage = new IncidentImage
    {
        ImageBytes = image.ToByteArray()
    };

image 是插件返回的 MediaFile.

image being the MediaFile returned by the plugin.

然后我的 XAML 看起来像这样

Then my XAML looks like this

<Image Source="{Binding IncidentImage.ImageSource}" Aspect="AspectFit"  />

您也可以通过将 ImageSource 代码移动到转换器来实现.

You could also do it by moving the ImageSource code to a converter.

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