在xamarin.forms中进行屏幕捕获

Question

是否有一个包在xamarin.forms中进行屏幕捕获？

我还需要捕获谷歌地图的屏幕截图

Answer 1

看看Daniel Hindrikes的这篇博客文章.

我将假设您使用PCL作为共享代码.

您需要在PCL中创建一个界面.他称之为IScreenshotManager.声明如下:

public interface IScreenshotManager
{
   Task<byte[]> CaptureAsync();
}

现在所有平台都有自己的实现.适用于iOS;

public class ScreenshotManager : IScreenshotManager
{
    public async System.Threading.Tasks.Task<byte[]> CaptureAsync()
    {
        var view = UIApplication.SharedApplication.KeyWindow.RootViewController.View;

        UIGraphics.BeginImageContext(view.Frame.Size);
        view.DrawViewHierarchy(view.Frame, true);
        var image = UIGraphics.GetImageFromCurrentImageContext();
        UIGraphics.EndImageContext();

        using(var imageData = image.AsPNG())
        {
            var bytes = new byte[imageData.Length];
            System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, bytes, 0, Convert.ToInt32(imageData.Length));
            return bytes;
        }

    }
}

对于Android:

public class ScreenshotManager : IScreenshotManager
{
    public static Activity Activity { get; set; }

    public async System.Threading.Tasks.Task<byte[]> CaptureAsync()
    {
        if(Activity == null)
        {
            throw new Exception("You have to set ScreenshotManager.Activity in your Android project");
        }

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

        Bitmap bitmap = view.GetDrawingCache(true);

        byte[] bitmapData;

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

        return bitmapData;
    }
}

对于Windows Phone:

public class ScreenshotManager : IScreenshotManager
{
    public async Task<byte[]> CaptureAsync()
    {
        var rootFrame = Application.Current.RootVisual as PhoneApplicationFrame;

        var screenImage = new WriteableBitmap((int)rootFrame.ActualWidth, (int)rootFrame.ActualHeight);
        screenImage.Render(rootFrame, new MatrixTransform());
        screenImage.Invalidate();

        using (var stream = new MemoryStream())
        {
            screenImage.SaveJpeg(stream, screenImage.PixelWidth, screenImage.PixelHeight, 0, 100);
            var bytes = stream.ToArray();
            return bytes;
        }
    }
}

不要忘记使用将其与依赖关系服务注册的属性注册您的平台特定实现,如下所示:

[assembly: Xamarin.Forms.Dependency (typeof (ScreenshotManager))]

它超越了名称空间声明.

现在,从您的共享代码中,您可以通过byte[]以下调用获取屏幕截图:

var screenshotBytes = DependencyService.Get<IScreenshotManager>().CaptureAsync();

您可能想在使用之前检查是否DependencyService.Get<IScreenshotManager>()没有null.

之后,你可以把你byte[]变成一个图像,用它做任何你喜欢的事情!