你必须自己写。了解WP电子商务的运作方式：

首先，“注册”主题文件的功能。

function wpsc_register_theme_file( $file_name ) {
    global $wpec_theme_files;

    if ( !in_array( $file_name, (array)$wpec_theme_files ) )
        $wpec_theme_files[] = $file_name;
}

然后是查找主题文件的函数：

/**
 * Checks the active theme folder for the particular file, if it exists then return the active theme directory otherwise
 * return the global wpsc_theme_path
 * @access public
 *
 * @since 3.8
 * @param $file string filename
 * @return PATH to the file
 */
 function wpsc_get_template_file_path( $file = \'\' ){

     // If we\'re not looking for a file, do not proceed
     if ( empty( $file ) )
         return;

     // No cache, so find one and set it
     if ( false === ( $file_path = get_transient( WPEC_TRANSIENT_THEME_PATH_PREFIX . $file ) ) ) {
         // Look for file in stylesheet
         if ( file_exists( get_stylesheet_directory() . \'/\' . $file ) ) {
             $file_path = get_stylesheet_directory() . \'/\' . $file;

         // Look for file in template
         } elseif ( file_exists( get_template_directory() . \'/\' . $file ) ) {
             $file_path = get_template_directory() . \'/\' . $file;

         // Backwards compatibility
         } else {
             // Look in old theme path
             $selected_theme_check = WPSC_OLD_THEMES_PATH . get_option( \'wpsc_selected_theme\' ) . \'/\' . str_ireplace( \'wpsc-\', \'\', $file );

             // Check the selected theme
             if ( file_exists( $selected_theme_check ) ) {
                 $file_path = $selected_theme_check;

             // Use the bundled file
             } else {
                 $file_path = WPSC_CORE_THEME_PATH . \'/\' . $file;
             }
         }
         // Save the transient and update it every 12 hours
         if ( !empty( $file_path ) )
             set_transient( WPEC_TRANSIENT_THEME_PATH_PREFIX . $file, $file_path, 60 * 60 * 12 );

     }elseif(!file_exists($file_path)){
         delete_transient(WPEC_TRANSIENT_THEME_PATH_PREFIX . $file);
         wpsc_get_template_file_path($file);
     }

     // Return filtered result
     return apply_filters( WPEC_TRANSIENT_THEME_PATH_PREFIX . $file, $file_path );
 }

在init钩子中，插件使用wpsc\\u register\\u theme\\u file（）注册它需要的所有主题文件：

wpsc_register_theme_file( \'wpsc-single_product.php\' );
wpsc_register_theme_file( \'wpsc-grid_view.php\' );
wpsc_register_theme_file( \'wpsc-list_view.php\' );
wpsc_register_theme_file( \'wpsc-products_page.php\' );
wpsc_register_theme_file( \'wpsc-shopping_cart_page.php\' );
wpsc_register_theme_file( \'wpsc-transaction_results.php\' );
wpsc_register_theme_file( \'wpsc-user-log.php\' );
wpsc_register_theme_file( \'wpsc-cart_widget.php\' );
wpsc_register_theme_file( \'wpsc-featured_product.php\' );
wpsc_register_theme_file( \'wpsc-category-list.php\' );
wpsc_register_theme_file( \'wpsc-category_widget.php\' ); 

然后，当实际需要该文件时，他们调用wpsc\\u get\\u template\\u file\\u path（）：

switch ( $display_type ) {
        case "grid":
            include( wpsc_get_template_file_path( \'wpsc-grid_view.php\' ) );
            break; // only break if we have the function;

        case "list":
            include( wpsc_get_template_file_path( \'wpsc-list_view.php\' ) );
            break; // only break if we have the file;
        default:
            include( wpsc_get_template_file_path( \'wpsc-products_page.php\' ) );
            break;
    }

显然，插件的代码看起来会有所不同，但原则应该是相同的。