How can I make playbin2 to close file and unload it?

[wl2776]

I use the following code:

g_main_loop_quit(m_loop);
gst_element_set_state(GST_ELEMENT(m_player),GST_STATE_NULL);
g_object_set(G_OBJECT(m_player),"uri",NULL,NULL);

However, videosink still displays a frame from a video, and a playing request still makes it to play.