Java Android棉花糖和棒棒糖中的文件下载失败

我创建了一个“MP4文件下载”按钮。它在安卓派和奥利奥中运行良好，但在棉花糖或棒棒糖中不起作用。它不会下载这些版本中的文件。有人能指出我的代码中缺少了什么吗？提前谢谢

这是我的下载代码

public class DownloadFile extends AsyncTask<String, String, String> {

    private ProgressDialog progressDialog;
    private String fileName;
    private String folder;
    private boolean isDownloaded;

    /**
     * Before starting background thread
     * Show Progress Bar Dialog
     */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        this.progressDialog = new ProgressDialog(context);
        this.progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        this.progressDialog.setCancelable(false);
        this.progressDialog.show();
    }

    /**
     * Downloading file in background thread
     */
    @Override
    protected String doInBackground(String... f_url) {
        int count;
        try {
            URL url = new URL(f_url[0]);
            URLConnection connection = url.openConnection();
            connection.connect();
            // getting file length
            int lengthOfFile = connection.getContentLength();


            // input stream to read file - with 8k buffer
            InputStream input = new BufferedInputStream(url.openStream(), 8192);

            String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());

            //Extract file name from URL
            fileName = f_url[0].substring(f_url[0].lastIndexOf('/') + 1, f_url[0].length());

            //Append timestamp to file name
            fileName = timestamp + "_" + fileName;

            //External directory path to save file
            folder = Environment.getExternalStorageDirectory() + File.separator + "Bharti News/";

            //Create androiddeft folder if it does not exist
            File directory = new File(folder);

            if (!directory.exists()) {
                directory.mkdirs();
            }

            // Output stream to write file
            OutputStream output = new FileOutputStream(folder + fileName);

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                // After this onProgressUpdate will be called
                publishProgress("" + (int) ((total * 100) / lengthOfFile));
                Log.d(TAG, "Progress: " + (int) ((total * 100) / lengthOfFile));

                // writing data to file
                output.write(data, 0, count);
            }

            // flushing output
            output.flush();

            // closing streams
            output.close();
            input.close();
            return "Downloaded at: " + folder + fileName;

        } catch (Exception e) {
            Log.e("Error: ", e.getMessage());
        }

        return "Something went wrong";
    }

    /**
     * Updating progress bar
     */
    protected void onProgressUpdate(String... progress) {
        // setting progress percentage
        progressDialog.setProgress(Integer.parseInt(progress[0]));
    }


    @Override
    protected void onPostExecute(String message) {
        // dismiss the dialog after the file was downloaded
        this.progressDialog.dismiss();

        // Display File path after downloading
        Toast.makeText(context,
                message, Toast.LENGTH_LONG).show();
    }
}

---

它给了我这个错误-“/storage/emulated/0/Bharti News/2019-05-22-02-19-09_dWJZ7AQesz48Ol2o.mp4:open failed:enoint（没有这样的文件或目录）”

您应该检查用户是否通过使用以下命令授予了外部存储的权限：

if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
    Log.v(TAG,"Permission is granted");
    new DownloadFile().execute(item.getBodyurl());
    return true;
}else{ ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);}

if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
    Log.v(TAG,"Permission is granted");
    new DownloadFile().execute(item.getBodyurl());
    return true;
}else{ ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);}