嗨~请教我如何在webview Android中下载文件？

如何解决嗨~请教我如何在webview Android中下载文件？

->文件下载正常，

但是，尽管设置了“utf-8”，字符还是出现了裂痕。

而且，它无法打开并发生错误。

我该怎么办？

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1. manifest 

<!--PERMISSIONS: for Storage-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

2. websetting on MainActivity

mWebView.setDownloadListener(new DownloadListener() {
    @RequiresApi(api = Build.VERSION_CODES.N)
    @Override
    public void onDownloadStart(String url,String userAgent,String contentdisposition,String mimetype,long contentLength) {
        try {
            DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
            DownloadManager dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);

            contentdisposition = URLDecoder.decode(contentdisposition,"UTF-8"); 

            
            String FileName = contentdisposition.replace("attachment; filename=","");

            String strcut = FileName.toString();
            FileName = strcut.substring(0,strcut.length()-1);

            String fileName = FileName; 

            request.setMimeType(mimetype);
            request.addRequestHeader("User-Agent",userAgent);
            request.setDescription("Downloading File");
            request.setAllowedOverMetered(true);
            request.setAllowedOverRoaming(true);
            request.setTitle(fileName);
            request.setRequiresCharging(false);

            request.allowScanningByMediaScanner();
            request.setAllowedOverMetered(true);
            request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
            request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,fileName);
            dm.enqueue(request);
            Toast.makeText(getApplicationContext(),"file is downloading.",Toast.LENGTH_LONG).show();
        }
        catch (Exception e) {
            if (ContextCompat.checkSelfPermission(MainActivity.this,android.Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,android.Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                    Toast.makeText(getBaseContext(),"permission is needed.",Toast.LENGTH_LONG).show();
                    ActivityCompat.requestPermissions(MainActivity.this,new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE},1004);
                }
                else {
                    Toast.makeText(getBaseContext(),"permission is needed",1004);
                }
            }
        }
    }
});