Android - Copy assets to internal storage

I did something like this. This allows you to copy all the directory structure to copy from Android AssetManager.

public String copyDirorfileFromAssetManager(String arg_assetDir, String arg_destinationDir) throws IOException
{
    File sd_path = Environment.getExternalStorageDirectory(); 
    String dest_dir_path = sd_path + addLeadingSlash(arg_destinationDir);
    File dest_dir = new File(dest_dir_path);

    createDir(dest_dir);

    AssetManager asset_manager = getApplicationContext().getAssets();
    String[] files = asset_manager.list(arg_assetDir);

    for (int i = 0; i < files.length; i++)
    {

        String abs_asset_file_path = addTrailingSlash(arg_assetDir) + files[i];
        String sub_files[] = asset_manager.list(abs_asset_file_path);

        if (sub_files.length == 0)
        {
            // It is a file
            String dest_file_path = addTrailingSlash(dest_dir_path) + files[i];
            copyAssetFile(abs_asset_file_path, dest_file_path);
        } else
        {
            // It is a sub directory
            copyDirorfileFromAssetManager(abs_asset_file_path, addTrailingSlash(arg_destinationDir) + files[i]);
        }
    }

    return dest_dir_path;
}


public void copyAssetFile(String assetFilePath, String destinationFilePath) throws IOException
{
    InputStream in = getApplicationContext().getAssets().open(assetFilePath);
    OutputStream out = new FileOutputStream(destinationFilePath);

    byte[] buf = new byte[1024];
    int len;
    while ((len = in.read(buf)) > 0)
        out.write(buf, 0, len);
    in.close();
    out.close();
}

public String addTrailingSlash(String path)
{
    if (path.charAt(path.length() - 1) != '/')
    {
        path += "/";
    }
    return path;
}

public String addLeadingSlash(String path)
{
    if (path.charAt(0) != '/')
    {
        path = "/" + path;
    }
    return path;
}

public void createDir(File dir) throws IOException
{
    if (dir.exists())
    {
        if (!dir.isDirectory())
        {
            throw new IOException("Can't create directory, a file is in the way");
        }
    } else
    {
        dir.mkdirs();
        if (!dir.isDirectory())
        {
            throw new IOException("Unable to create directory");
        }
    }
}

Use

 String out= Environment.getExternalStorageDirectory().getAbsolutePath() + "/X/Y/Z/" ; 

        File outFile = new File(out, Filename);

After Editing in your ref. Link Answer.

private void copyAssets() {
    AssetManager assetManager = getAssets();
    String[] files = null;
try {
    files = assetManager.list("");
} catch (IOException e) {
    Log.e("tag", "Failed to get asset file list.", e);
  }
 for(String filename : files) {
    InputStream in = null;
    OutputStream out = null;
    try {
      in = assetManager.open(filename);

      String outDir = Environment.getExternalStorageDirectory().getAbsolutePath() + "/X/Y/Z/" ; 

      File outFile = new File(outDir, filename);

      out = new FileOutputStream(outFile);
      copyFile(in, out);
      in.close();
      in = null;
      out.flush();
      out.close();
        out = null;
      } catch(IOException e) {
          Log.e("tag", "Failed to copy asset file: " + filename, e);
         }       
       }
     }
     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);
     }
   }