You not always can create a working file from a content URI. But you likely don't need it. new CSVReader(fr); accepts a Reader as a parameter. You can use InputStreamReader, created from the InputStream, created from the Uri using following method:

InputStream  inputStream = getContentResolver().openInputStream(uri);

where uri is data.getData()

There are file explorer style apps that will open it. Or you could download Csv Viewer app from Play Store.

Blurb from it.

CSV File Viewer For Android | CSV Reader - view small and large-sized CSV files.

CSV Reader - Simple, fast, and powerful tool for reading csv files.

I am not associated with it.

As per this stackoverflow question's accepted answer, you could try this:

public String readFileFromDownloads(String fileName) {
    File downloadsDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
    if (!downloadsDir.exists()) return null;

    File file = new File(downloadsDir, fileName);
    if (!file.exists()) return null;

    try {
        StringBuilder fileContent = new StringBuilder();
        BufferedReader br = new BufferedReader(new FileReader(file));

        String line;
        while ((line = br.readLine()) != null) {
            fileContent.append(line);
            fileContent.append('\n');
        }
        br.close();

        return fileContent.toString();
    } catch (IOException ex) {
        //Handle error
        return null;
    }
}

And then call readFileFromDownloads("MyDocument.csv"); from inside your onClick(); method.

Also, you might need to add android.permission.READ_EXTERNAL_STORAGE to your Manifest and handle Android 6.0 new permission system as per Android Docs.

To read data from internal storage you need your app files folder and read content from here :

File yourFile = new File(context.getFilesDir() + "/" + "File_Name.extension");
FileInputStream fis = null;
        try {
            fis = new FileInputStream(yourFile);
            InputStreamReader isr = new InputStreamReader(fis);
            BufferedReader bufferedReader = new BufferedReader(isr);
            StringBuilder sb = new StringBuilder();
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                sb.append(line);
            }
            return sb.toString();
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        }

Also you can use this approach :

FileInputStream fis = context.openFileInput("hello.txt", Context.MODE_PRIVATE);
   InputStreamReader isr = new InputStreamReader(fis);
   BufferedReader bufferedReader = new BufferedReader(isr);
   StringBuilder sb = new StringBuilder();
   String line;
   while ((line = bufferedReader.readLine()) != null) {
       sb.append(line);
   }

I have something like this;

public final List<String[]> readCsv(Context context) {
  List<String[]> questionList = new ArrayList<String[]>();
  AssetManager assetManager = context.getAssets();

  try {
    InputStream csvStream = assetManager.open(CSV_PATH);
    InputStreamReader csvStreamReader = new InputStreamReader(csvStream);
    CSVReader csvReader = new CSVReader(csvStreamReader);
    String[] line;

    // throw away the header
    csvReader.readNext();

    while ((line = csvReader.readNext()) != null) {
      questionList.add(line);
    }
  } catch (IOException e) {
    e.printStackTrace();
  }
  return questionList;
}