Javascript 从Android Webview中的Blob下载视频

我正在将我的网络摄像头录制保存到blob，然后下载它。现在，我需要在android中使用视频录制调用相同的web视图。我无法从Blob URL下载该文件

这是我的密码

webview.setDownloadListener(new DownloadListener() {
        @Override
        public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimeType, long contentLength) {
           webview.loadUrl(JavaScriptInterface.getBase64StringFromBlobUrl(url));
        }
    });

JavascriptInterface类如下所示

@JavascriptInterface
public void getBase64FromBlobData(String base64Data) throws IOException {
    convertBase64StringToPdfAndStoreIt(base64Data);
}
public static String getBase64StringFromBlobUrl(String blobUrl) {
    if(blobUrl.startsWith("blob")){
        return "javascript: var xhr = new XMLHttpRequest();" +
                "xhr.open('GET', '"+ blobUrl +"', true);" +
                "xhr.setRequestHeader('Content-type','video/webm');" +
                "xhr.responseType = 'blob';" +
                "xhr.onload = function(e) {" +
                "    if (this.status == 200) {" +
                "        var blobPdf = this.response;" +
                "        var reader = new FileReader();" +
                "        reader.readAsDataURL(blobPdf);" +
                "        reader.onloadend = function() {" +
                "            base64data = reader.result;" +
                "            Android.getBase64FromBlobData(base64data);" +
                "        }" +
                "    }" +
                "};" +
                "xhr.send();";
    }
    return "javascript: console.log('It is not a Blob URL');";
}
private void convertBase64StringToPdfAndStoreIt(String base64PDf) throws IOException {
    final int notificationId = 1;
    String currentDateTime = getDateTimeInstance().format(new Date());
    final File dwldsPath = new File(Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_DOWNLOADS) + "/YourFileName_" + currentDateTime + "_.pdf");
    byte[] pdfAsBytes = Base64.decode(base64PDf.replaceFirst("^data:application/pdf;base64,", ""), 0);
    FileOutputStream os;
    os = new FileOutputStream(dwldsPath, false);
    os.write(pdfAsBytes);
    os.flush();

    if (dwldsPath.exists()) {
        Intent intent = new Intent();
        intent.setAction(android.content.Intent.ACTION_VIEW);
        Uri apkURI = FileProvider.getUriForFile(context,context.getApplicationContext().getPackageName() + ".provider", dwldsPath);
        intent.setDataAndType(apkURI, MimeTypeMap.getSingleton().getMimeTypeFromExtension("pdf"));
        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        PendingIntent pendingIntent = PendingIntent.getActivity(context,1, intent, PendingIntent.FLAG_CANCEL_CURRENT);
        String CHANNEL_ID = "MYCHANNEL";
        final NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            NotificationChannel notificationChannel= new NotificationChannel(CHANNEL_ID,"name", NotificationManager.IMPORTANCE_LOW);
            Notification notification = new Notification.Builder(context,CHANNEL_ID)
                    .setContentText("You have got something new!")
                    .setContentTitle("File downloaded")
                    .setContentIntent(pendingIntent)
                    .setChannelId(CHANNEL_ID)
                    .setSmallIcon(android.R.drawable.sym_action_chat)
                    .build();
            if (notificationManager != null) {
                notificationManager.createNotificationChannel(notificationChannel);
                notificationManager.notify(notificationId, notification);
            }

        } else {
            NotificationCompat.Builder b = new NotificationCompat.Builder(context, CHANNEL_ID)
                    .setDefaults(NotificationCompat.DEFAULT_ALL)
                    .setWhen(System.currentTimeMillis())
                    .setSmallIcon(android.R.drawable.sym_action_chat)
                    //.setContentIntent(pendingIntent)
                    .setContentTitle("MY TITLE")
                    .setContentText("MY TEXT CONTENT");

            if (notificationManager != null) {
                notificationManager.notify(notificationId, b.build());
                Handler h = new Handler();
                long delayInMilliseconds = 1000;
                h.postDelayed(new Runnable() {
                    public void run() {
                        notificationManager.cancel(notificationId);
                    }
                }, delayInMilliseconds);
            }
        }
    }
    Toast.makeText(context, "PDF FILE DOWNLOADED!", Toast.LENGTH_SHORT).show();
}

请告诉我我做错了什么