I can't copy file or other operate in U disk when the code runs in Android P on TV

Question

I can't copy or move the file from U disk when I run my code on Android P and throw the exception said 'permission denied'. the same code runs on 8.0 or lower works good. I use the FileInputStream and FileOutputStream to copy the file in U disk.

I've declared permission about android.permission.READ_EXTERNAL_STORAGE and android.permission.WRITE_EXTERNAL_STORAGE. But it still doesn't work.

 private int copyFileUsingFileStreams(File source, File dest)
        throws IOException {
    int resultCode = 0;

    InputStream input = null;
    OutputStream output = null;
    try {
        input = new FileInputStream(source);
        output = new FileOutputStream(dest);
        byte[] buf = new byte[2048];
        int bytesRead;
        while ((bytesRead = input.read(buf)) != -1) {
            if (isInterrupted()) {
                resultCode = ZFileManager.OperateResult.USER_CANCLE;
                input.close();
                output.close();
                break;
            }
            output.write(buf, 0, bytesRead);
        }
    } finally {
        if (input != null) {
            input.close();
        }
        if (output != null) {
            output.close();
        }
    }

    return resultCode;
}