如何使用存储访问框架android将文件保存到下载文件夹？

implementation 'androidx.documentfile:documentfile:1.0.1'

private static final int REQUEST_CODE = 1;

private void requestStoragePermission() {
    Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
    startActivityForResult(intent, REQUEST_CODE);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
        Uri treeUri = data.getData();
        // 保存授权的treeUri，后续使用
    }
}

private void saveFileToDownloads(Uri treeUri, String fileName, String mimeType, byte[] fileData) {
    DocumentFile downloadsDir = DocumentFile.fromTreeUri(this, treeUri);
    DocumentFile file = downloadsDir.createFile(mimeType, fileName);
    try {
        OutputStream outputStream = getContentResolver().openOutputStream(file.getUri());
        outputStream.write(fileData);
        outputStream.close();
        // 文件保存成功
    } catch (IOException e) {
        e.printStackTrace();
        // 文件保存失败
    }
}