将布局保存到位图（Xamarin）

Question

I have layout and need to save it to bitmap

here is code

public void Save()
{
    LinearLayout view = FindViewById<LinearLayout>(Resource.Id.badge);

    view.DrawingCacheEnabled = true;
    view.BuildDrawingCache();
    Bitmap layout = view.GetDrawingCache(true);

}

I set breakpoint to Bitmap layout = view.GetDrawingCache(true); and I see that's layout is null.

Where is my mistake, how to save layout to bitmap?

UPDATE

I try to save view to bitmap like this

public  Bitmap CreateBitmapFromView(View view, bool autoScale = true)
    {
        var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
        view.DrawingCacheEnabled = true;
        view.BuildDrawingCache(autoScale);
        var bitmap2 = view.GetDrawingCache(autoScale);
        view.DrawingCacheEnabled = wasDrawingCacheEnabled;
        return bitmap2;

    }

All ok, bitmap2 is returning.

But also I need to save it to SD

I wrote method like this

public  Bitmap CreateBitmapFromView(View view, bool autoScale = true)
    {
        var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
        view.DrawingCacheEnabled = true;
        view.BuildDrawingCache(autoScale);
        var bitmap2 = view.GetDrawingCache(autoScale);
        view.DrawingCacheEnabled = wasDrawingCacheEnabled;
        var sdCardPath = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
        var filePath = System.IO.Path.Combine(sdCardPath, "test.png");
        var stream = new FileStream(filePath, FileMode.Create);
        bitmap2.Compress(Bitmap.CompressFormat.Png, 100, stream);
        return bitmap2;

    }

And have this error.

Object reference not set to an instance of an object.

Answer 1

change it to something likes this :

public Bitmap CreateBitmapFromView(View view, bool autoScale = true)
{
    var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
    view.DrawingCacheEnabled = true;
    view.BuildDrawingCache(autoScale);
    var bitmap = view.GetDrawingCache(autoScale);
    view.DrawingCacheEnabled = wasDrawingCacheEnabled;
    return bitmap;
}

UPDATE

try to define var bitmap2 as global variable

public  Bitmap CreateBitmapFromView(View view, bool autoScale = true)
    {
        var wasDrawingCacheEnabled = view.DrawingCacheEnabled;
        view.DrawingCacheEnabled = true;
        view.BuildDrawingCache(autoScale);
        view.DrawingCacheEnabled = wasDrawingCacheEnabled;
        var sdCardPath = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
        var filePath = System.IO.Path.Combine(sdCardPath, "test.png");
        var stream = new FileStream(filePath, FileMode.Create);
        bitmap2.Compress(Bitmap.CompressFormat.Png, 100, stream);
        return bitmap2;
    }