White Screen when i did a screenshot on Android using Mapsui

Question

I using mapsui to show an IGN map on my application and I want to make a screenshot of the map when I click on a specific button. So I use dependency injection and It works perfectly on UWP. But with Android, I can't screen the map and I have a white screen. There is my code for Android :

public Task<byte[]> TakeShot()
    {
        var _activity = CrossCurrentActivity.Current;
        if (_activity == null)
        {
            throw new Exception("You have to set ScreenshotManager.Activity in your Android project");
        }

        var view = _activity.Activity.Window.DecorView;
        view.DrawingCacheEnabled = true;

        Bitmap bitmap = view.GetDrawingCache(true);
        view.BuildDrawingCache();

        byte[] bitmapData;

        using (var stream = new MemoryStream())
        {
            bitmap.Compress(Bitmap.CompressFormat.Png, 0, stream);
            bitmapData = stream.ToArray();
        }

        return Task.FromResult(bitmapData);
    }

Only the map is blank, because I have my button on the image. Thank's for your help

Answer 1

I used the Mapsui, then I create a screenshot function with dependence service, Here is my GIF when take a screemshot.

Here is my dependence service about achieveing screenshot.

[assembly: Dependency(typeof(ScreenshotService))]
namespace MVVMDataBinding.Droid
{
 public class ScreenshotService : IScreenshotService
 {

    public byte[] Capture()
    {

       var _activity = CrossCurrentActivity.Current;

        var rootView = _activity.Activity.Window.DecorView;

        using (var screenshot = Bitmap.CreateBitmap(
                                rootView.Width,
                                rootView.Height,
                                Bitmap.Config.Argb8888))
        {
            var canvas = new Canvas(screenshot);
            rootView.Draw(canvas);

            using (var stream = new MemoryStream())
            {
                screenshot.Compress(Bitmap.CompressFormat.Png, 90, stream);
                return stream.ToArray();
            }
        }
    }
   }
}

And create an interface IScreenshotService in the xamarin forms.

   public interface IScreenshotService
{
    byte[] Capture();
}

Use it in the xamarin forms.

private void Button_Clicked(object sender, EventArgs e)
    {
        var screenshotData = DependencyService.Get<IScreenshotService>().Capture();
        myImage.Source=ImageSource.FromStream(() => new 
        MemoryStream((byte[])screenshotData));
    }

forground code.

  <ContentPage.Content>
    <StackLayout>
    <Grid x:Name="ContentGrid"  WidthRequest="100" HeightRequest="200" />

    <Button Text="Take a screen" Clicked="Button_Clicked"/>

    <Image x:Name="myImage" WidthRequest="200" HeightRequest="300"/>
    </StackLayout>
</ContentPage.Content>

Here is my demo.

https://github.com/851265601/MapsuiWithScreenshotDemo