Question

简单代码：

((WebKit.DOM.EventTarget) img).add_event_listener_with_closure ("click", on_enter, false);

void on_enter() {

}

valac错误：

error: Argument 2: Cannot convert from `on_enter' to `GLib.Closure'

以下是完整的代码示例：

private void on_click(WebKit.DOM.EventTarget target, WebKit.DOM.Event event)
{
  try
  {
    //var image = (WebKit.DOM.HTMLImageElement)target;
    //image.set_attribute("class", "clickable-img-hover");
  }
  catch(GLib.Error e)
  {
  }
}

public static void webkit_web_extension_initialize (WebKit.WebExtension web_extension)
{
  string PROG = "[webkit2_webextension_minimal_so.so] ";    

  print(PROG + "PLUGIN activated\n");

  web_extension.page_created.connect((extension, web_page)=> {
      print(PROG + "SIGNAL: page_created\n");
      try {
        var dom = web_page.get_dom_document();

        WebKit.DOM.Element img = dom.create_element("img");
        img.set_attribute("src", "file:///home/o/avatar.png");
        img.set_attribute("alt", "avatar-1.jpg");
        ((WebKit.DOM.EventTarget) img).add_event_listener_with_closure("click", on_click, false);
        dom.body.insert_before(img, null);
      } catch (FileError e) {
        stdout.printf ("Message: \"%s\"\n", e.message);
            stdout.printf ("Error code: FileError.EXIST = %d\n", e.code);
            stdout.printf ("FileErrors identification: %" + uint32.FORMAT + "\n", e.domain);
        }

      web_page.send_request.connect((request)=> {
          if(request.uri.has_prefix("http://www.google") || request.uri.has_prefix("data")){
            print(PROG + "SIGNAL: send request [REJECTED] " + request.uri + "\n");
            return true;  // true => block query
          }
          print(PROG + "SIGNAL: send request " + request.uri + "\n");
          return false;
        });

      return;
    });
}

编译：

valac --pkg glib-2.0 --pkg webkit2gtk-web-extension-4.0 --library=webext webext.vala -H webext.h -X -fPIC -X -shared -o webext.so

如何添加事件监听器？

PS：这是对this earlier question的跟进问题。

Answer 1

查看documentation for the method：

public bool add_event_listener_with_closure (
    string event_name,
    owned EventTargetFunc handler,
    bool use_capture
)

第二个参数是owned EventTargetFunc handler。

所以看看documentation of the delegate type：

public delegate void EventTargetFunc (EventTarget target, Event event)

您的方法没有此delgate类型。

因此，您可能必须将方法签名修改为：

void on_enter (EventTarget target, Event event) {

}

如何添加事件监听器？

1 个答案: