问在自定义插件页面中添加metabox

EN

add_action('admin_menu', 'wp_init_my_plugin');
function add_metabox(){
    add_action('add_meta_boxes', 'metabox');
};
function wp_init_my_plugin() {
    add_menu_page('Config', 'My Plugin', 'administrator', 'my_plugin', 'add_metabox');
};
function metabox()
{
    add_meta_box('box_id', 'The Title', 'metabox_content', 'my_plugin');
}
function metabox_content()
{
     echo "Where is batman?";
}