问如何在android中刷新资产文件列表

EN

private void copyAssetManual(){
    AssetManager assetManager = getAssets();
    String[] files = null;
    try{
        files = assetManager.list("Manual");
        Log.d(TAG, "Files String Array Length: " + files.length);
    }catch(IOException e){
        Log.d(TAG, e.getMessage());
    }

    for(String filename : files){
        Log.d(TAG, "copyAssetManual: " + filename);
        InputStream in = null;
        OutputStream out = null;
        try{
            in = assetManager.open("Manual/" + filename);
            out = new FileOutputStream(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).toString() + "/" + filename);
            copyFile(in, out);
            in.close();
            in = null;
            out.flush();
            out.close();
            out = null;
        }catch(Exception e){
            Log.d(TAG, e.getMessage());
        }

        //Auto Execute Copied File
        File userManual = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), filename);
        String extension = MimeTypeMap.getFileExtensionFromUrl(filename);
        String mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension.toLowerCase());
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(Uri.fromFile(userManual), mimeType);
        startActivity(intent);
    }
}

private void copyFile(InputStream in, OutputStream out) throws IOException{
    byte[] buffer = new byte[1024];
    int read;
    while((read = in.read(buffer)) != -1){
        out.write(buffer, 0, read);
    }
}