侦听dbus信号

Question

我正在尝试从c代码中监听dbus-event。我可以通过dbus-monitor事件捕获它们。

dbus-monitor --session --monitor "type='signal',interface='org.jwz.XScreensaver'"

signal sender=org.freedesktop.DBus -> dest=:1.146 serial=2 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=NameAcquired
   string ":1.146"

signal sender=:1.96 -> dest=(null destination) serial=40 path=/org/jwz/XScreensaver; interface=org.jwz.XScreensaver; member=ScreensaverStarted
signal sender=:1.96 -> dest=(null destination) serial=41 path=/org/jwz/XScreensaver; interface=org.jwz.XScreensaver; member=ScreensaverStopped

当我尝试从c代码看不到的时候也是一样的。不确定我遗漏了哪里，要么是回调没有签名，要么是事件是预期的，要么是我的路径/接口错误。以下是代码

static void
test_hint_signal_handler (DBusGProxy * proxy,
       gpointer user_data)
{
  printf("I am here");
}

gint
main (gint argc, gchar *argv[])
{
  printf("In Main\n");
  DBusGConnection *dbus_glib_connection = NULL;
  GMainLoop *loop = NULL;
  GError *error = NULL;
  DBusGProxy *control_proxy = NULL;

  g_type_init ();

  loop = g_main_loop_new (NULL, FALSE);

  dbus_glib_connection = dbus_g_bus_get (DBUS_BUS_SYSTEM, &error);
  if (error != NULL)
    {
      g_warning ("Failed connecting to system bus: %s", error->message);
      dbus_glib_connection = NULL;
      g_error_free (error);
    }
  if (dbus_glib_connection != NULL)
    {
      control_proxy = dbus_g_proxy_new_for_name( dbus_glib_connection,
            "org.jwz.XScreensaver",
            "/org/jwz/XScreensaver",
            "org.jwz.XScreensaver"
            );
      if (control_proxy == NULL)
    {
      g_warning ("Failed to get proxy");
    }
    }
  if (control_proxy != NULL)
    {
        dbus_g_proxy_add_signal( control_proxy,
            "ScreensaverStarted",
            G_TYPE_INVALID
            );

    dbus_g_proxy_connect_signal( control_proxy,
            "ScreensaverStarted",
            G_CALLBACK(test_hint_signal_handler),
            NULL,
            NULL
            );

    }

  g_debug("Starting mainloop");
  g_main_loop_run (loop);

  return 0;
}

编辑:代码不存在。它正在等待事件的到来。以下是编译时的警告

dbus-test-client.c: In function ‘main’:
dbus-test-client.c:20:3: warning: ‘g_type_init’ is deprecated [-Wdeprecated-declarations]
   g_type_init ();
   ^
In file included from /usr/include/glib-2.0/gobject/gobject.h:24:0,
                 from /usr/include/glib-2.0/gobject/gbinding.h:29,
                 from /usr/include/glib-2.0/glib-object.h:23,
                 from /usr/include/dbus-1.0/dbus/dbus-glib.h:27,
                 from dbus-test-client.c:2:
/usr/include/glib-2.0/gobject/gtype.h:681:23: note: declared here
 void                  g_type_init                    (void);
                       ^

Answer 1

在最上面的代码中添加了--会话参数(使用会话总线)，而在最下面的C代码中连接到系统总线(DBUS_BUS_SYSTEM)。在C代码中将系统总线切换到会话总线(DBUS_BUS_SESSION)，它将工作：

dbus_glib_connection = dbus_g_bus_get (DBUS_BUS_SESSION, &error);