如何使用Python持续监控Rhythmbox的曲目变化

Question

运行以下Python代码，来自于这个StackOverflow的回答

#!/usr/bin/python

import dbus
import dbus.mainloop.glib
import glib

# This gets called whenever Rhythmbox sends the playingUriChanged signal
def playing_song_changed (uri):
    global shell
    if uri != "":
    song = shell.getSongProperties (uri)
    print "Now playing: {0}".format (song["title"])
    else:
    print "Not playing anything"

dbus.mainloop.glib.DBusGMainLoop (set_as_default = True)

bus = dbus.SessionBus ()

proxy = bus.get_object ("org.gnome.Rhythmbox", "/org/gnome/Rhythmbox/Player")
player = dbus.Interface (proxy, "org.gnome.Rhythmbox.Player")
player.connect_to_signal ("playingUriChanged", playing_song_changed)

proxy = bus.get_object ("org.gnome.Rhythmbox", "/org/gnome/Rhythmbox/Shell")
shell = dbus.Interface (proxy, "org.gnome.Rhythmbox.Shell")

# Run the GLib event loop to process DBus signals as they arrive
mainloop = glib.MainLoop ()
mainloop.run ()

在Ubuntu 12.04和14.04上会出现以下错误：

Traceback (most recent call last):
  File "./test.py", line 20, in <module>
    proxy = bus.get_object ("org.gnome.Rhythmbox", "/org/gnome/Rhythmbox/Player")
  File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 241, in get_object
    follow_name_owner_changes=follow_name_owner_changes)
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 248, in __init__
    self._named_service = conn.activate_name_owner(bus_name)
  File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 180, in activate_name_owner
    self.start_service_by_name(bus_name)
  File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 278, in start_service_by_name
    'su', (bus_name, flags)))
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Rhythmbox was not provided by any .service files

我哪里做错了？

或者，如果有其他方法可以在Python中监听DBUS信号，那也会很有帮助。

Answer 1

结果我被那些缩写搞糊涂了，走了错路。

在Rhythmbox 3之前，Rhythmbox是通过它自己特有的API来控制的，这个API是基于DBUS协议的。

而在Rhythmbox 3之后，Rhythmbox通过MPRIS2 DBUS插件，使用一个通用的MPRIS2 API来控制，这同样是基于DBUS协议的。

所以我在网上搜索“Rhythmbox DBUS”其实是在浪费时间。

如果你也想做和我一样的事情：只需要搜索“MPRIS2 $你想用的编程语言$”，这样就能找到一个通用的方法来控制几乎所有的Linux音乐播放器。以Python为例，这里有一些链接：

https://github.com/hugosenari/mpris2

https://github.com/emesene/emesene-supported-plugins/blob/master/music/handler_mpris2.py

Answer 2

这个方法在 Rhythmbox 3 上可以用。我把它改成了把当前播放的歌曲写入一个文件（ ~/.now_playing ），不过你可以根据自己的需要进行调整：

#!/usr/bin/python

import dbus
import dbus.mainloop.glib
import glib

# This gets called whenever Rhythmbox sends the playingUriChanged signal
def playing_song_changed (Player,two,three):
    global iface
    global track
    global home
    track2 = iface.Get(Player,"Metadata").get(dbus.String(u'xesam:artist'))[0] + " - "+ iface.Get(Player,"Metadata").get(dbus.String(u'xesam:title'))

    if track != track2:
        track = iface.Get(Player,"Metadata").get(dbus.String(u'xesam:artist'))[0] + " - "+ iface.Get(Player,"Metadata").get(dbus.String(u'xesam:title'))
        f = open( home + '/.now_playing', 'w' )
        f.write( track + '\n' )
        f.close()


dbus.mainloop.glib.DBusGMainLoop (set_as_default = True)

bus = dbus.SessionBus ()
from os.path import expanduser
home = expanduser("~")
player = bus.get_object ("org.mpris.MediaPlayer2.rhythmbox", "/org/mpris/MediaPlayer2")
iface = dbus.Interface (player, "org.freedesktop.DBus.Properties")

track = iface.Get("org.mpris.MediaPlayer2.Player","Metadata").get(dbus.String(u'xesam:artist'))[0] + " - "+ iface.Get("org.mpris.MediaPlayer2.Player","Metadata").get(dbus.Strin$
f = open( home + "/.now_playing", 'w' )
f.write( track + '\n' )
f.close()

iface.connect_to_signal ("PropertiesChanged", playing_song_changed)

# Run the GLib event loop to process DBus signals as they arrive
mainloop = glib.MainLoop ()
mainloop.run ()