How to save image in gallery when APILevel>29?

Question

[Xamarin.Forms Android]
My app will download image from server and save to gallery, I try this:

                Android.Net.Uri u = null;  
                if (Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.Q)  
                {  
                    ContentValues values = new ContentValues();  
                    values.Put(MediaStore.IMediaColumns.MimeType, "image/jpeg");  
                    values.Put(MediaStore.IMediaColumns.DateAdded, Java.Lang.JavaSystem.CurrentTimeMillis());  
                    values.Put(MediaStore.IMediaColumns.DisplayName, filename);  
                    var cr = MainActivity.AndroidContext.ContentResolver;  
                    u = cr.Insert(MediaStore.Images.Media.ExternalContentUri, values);  
                    var s = cr.OpenOutputStream(u);  
                    s.Write(data, 0, data.Length);  
                    s.Close();  
  
                    values.Clear();  
                    values.Put(MediaStore.IMediaColumns.IsPending, false);  
                    int updated = cr.Update(u, values, null, null);  
                }  

After running this code, I can confirm that image was save to:
/storage/emulated/0/Pictures/xxxxxxxxxxxx.jpg

But I can not see it in gallery, how to make it show in gallery?