DBus 信号接收器从不被调用答案

【问题标题】：DBus signal receivers are never calledDBus 信号接收器从不被调用
【发布时间】：2020-09-17 08:31:27
【问题描述】：

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，当我运行此代码时，我收到 no 信号。问题是当我在 CLI 中运行 dbus-monitor --system 时，我确实在插入 USB 设备时看到了这些消息。知道如何调试吗？还是我在这里做错了什么？

【问题讨论】：

标签： python dbus

【解决方案1】：

您使用的是什么 D-Bus 绑定？

我发现pydbus 绑定在 Python 中更容易使用。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
>>>

【讨论】：

【解决方案2】：

您很可能忘记设置事件循环（将您的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()

【讨论】：