DBus信号接收器从不被调用

Question

在我的代码中，我注册以在插入USB设备时接收信号。

def registerSignals(self):
for signal, callback, bus, interface in (('InterfacesAdded', self.onUSBInterfaceAdded, 'org.freedesktop.UDisks2', 'org.freedesktop.DBus.ObjectManager'),
('InterfacesRemoved', self.onUSBInterfaceRemoved, 'org.freedesktop.UDisks2', 'org.freedesktop.DBus.ObjectManager'),
('PropertiesChanged', self.onUSBMountPropertiesChanged, 'org.freedesktop.UDisks2', 'org.freedesktop.DBus.ObjectManager')):
print(self.__bus.add_signal_receiver(callback,
bus_name=bus,
signal_name=signal,
dbus_interface=interface))

def onUSBInterfaceAdded(self, path, interfaces):
print(path)
print(interfaces)
def onUSBInterfaceRemoved(self, path, interfaces):
print(path)
print(interfaces)
def onUSBMountPropertiesChanged(self, interface, properties, invalidated, path):
print(path)
print(interfaces)

现在，当我运行这个代码时，我得到没有信号。问题是，当我在CLI中运行dbus-monitor --system时，插入USB设备时确实会看到消息。知道如何调试这个吗？或者我在这里做错了什么？

Answer 1

您使用的是什么D-Bus绑定？

我发现在Python中使用pydbus绑定要容易得多。例如：

(venv) pi@raspberrypi:~/stack_overflow $ python3
Python 3.7.3 (default, Dec 20 2019, 18:57:59) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pydbus
>>> udisk2 = pydbus.SystemBus().get('.UDisks2')
>>> udisk2.on <-tab complete pressed->
udisk2.onInterfacesAdded    udisk2.onInterfacesRemoved  udisk2.onPropertiesChanged  
>>> udisk2.onInterfacesAdded = print
>>> 

Answer 2

您很可能忘记设置事件循环(将示例转换为普通函数(：

import dbus
from dbus.mainloop.glib import DBusGMainLoop
from gi.repository import GLib

def registerSignals():
for signal, callback, bus, interface in (('InterfacesAdded', onUSBInterfaceAdded, 'org.freedesktop.UDisks2', 'org.freedesktop.DBus.ObjectManager'),
('InterfacesRemoved', onUSBInterfaceRemoved, 'org.freedesktop.UDisks2', 'org.freedesktop.DBus.ObjectManager'),
('PropertiesChanged', onUSBMountPropertiesChanged, 'org.freedesktop.UDisks2', 'org.freedesktop.DBus.ObjectManager')):
print(dbus.SystemBus().add_signal_receiver(callback,
bus_name=bus,
signal_name=signal,
dbus_interface=interface))

def onUSBInterfaceAdded(path, interfaces):
print(path)
print(interfaces)

def onUSBInterfaceRemoved(path, interfaces):
print(path)
print(interfaces)

def onUSBMountPropertiesChanged(interface, properties, invalidated, path):
print(path)
print(interfaces)

DBusGMainLoop(set_as_default=True)
bus = dbus.SystemBus()
registerSignals()
GLib.MainLoop().run()