Xamarin.Android - 下载pdf和视频到应用空间并打开

Stream fos = OpenFileOutput(pdfName, FileCreationMode.WorldReadable);
            using (fos)
            {
                fos.Write(fileBytes,0,fileBytes.Length);
            }

Java.IO.File pdfFile = Application.Context.GetFileStreamPath(pdfName); 
            if (pdfFile.Exists())
            {
                Android.Net.Uri path = Android.Net.Uri.FromFile(pdfFile);

                Intent intent = new Intent(Intent.ActionView);
                intent.SetDataAndType(path, "application/pdf");
                intent.SetFlags(ActivityFlags.NewTask);

                try
                {
                    Application.Context.StartActivity(intent);
                }
                catch (ActivityNotFoundException ex)
                {
                    System.Diagnostics.Debug.WriteLine("no app installed to view the pdf");
                }
            }

videoView.SetVideoPath(internalPath);
            videoView.Start();