如何使用QThread的回调函数？
回调函数on_message不打印任何数据。 在run（）中，我连接到mqtt-broker并订阅主题。收到新消息时on_message必须正常工作。
简单的QT应用示例。与简单的QLCD连接的更改值事件。订阅主题来自dashboard
#!/usr/bin/python3
# -*- coding: utf-8 -*-
import sys
from PyQt5.QtCore import Qt, QThread, pyqtSignal
from PyQt5.QtWidgets import (QWidget, QLCDNumber, QSlider,
QVBoxLayout, QApplication)
from random import uniform, normalvariate, randint
import time
import paho.mqtt.client as mqtt
import paho.mqtt.subscribe as subscribe
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
lcd = QLCDNumber(self)
self.data=DataThread()
vbox = QVBoxLayout()
vbox.addWidget(lcd)
self.setLayout(vbox)
self.data.valueChanged.connect(lcd.display)
self.setGeometry(300, 300, 250, 150)
self.setWindowTitle('Callback')
self.data.start()
self.show()
class DataThread(QThread):
valueChanged = pyqtSignal(object)
val=0
def on_message(mqttc, obj, msg):
mstr=msg.payload.decode("ascii")
val=mstr
self.valueChanged.emit(val)
def on_subscribe(mqttc, obj, mid, granted_qos):
print("Subscribed: "+str(mid)+" "+str(granted_qos))
def run(self):
msg = subscribe.simple("shok2", hostname="broker.hivemq.com")
print("%s %s" % (msg.topic, msg.payload))
mqttc = mqtt.Client()
mqttc.on_subscribe = self.on_subscribe
mqttc.on_message = self.on_message
mqttc.connect("broker.hivemq.com")
print("subsrcibe")
mqttc.subscribe("shok2")
mqttc.loop_forever()
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
答案 0 :(得分：1)
不必使用线程，只需遵循Qt的逻辑：让我们使用信号。在下面的代码中，我展示了我正在实现的MQTT客户端库的高级功能，至少到目前为止，它可以实现所需的功能，在接下来的几天中，我将添加更多功能。
from PyQt5 import QtCore, QtWidgets
import paho.mqtt.client as mqtt
class MqttClient(QtCore.QObject):
Disconnected = 0
Connecting = 1
Connected = 2
MQTT_3_1 = mqtt.MQTTv31
MQTT_3_1_1 = mqtt.MQTTv311
connected = QtCore.pyqtSignal()
disconnected = QtCore.pyqtSignal()
stateChanged = QtCore.pyqtSignal(int)
hostnameChanged = QtCore.pyqtSignal(str)
portChanged = QtCore.pyqtSignal(int)
keepAliveChanged = QtCore.pyqtSignal(int)
cleanSessionChanged = QtCore.pyqtSignal(bool)
protocolVersionChanged = QtCore.pyqtSignal(int)
messageSignal = QtCore.pyqtSignal(str)
def __init__(self, parent=None):
super(MqttClient, self).__init__(parent)
self.m_hostname = ""
self.m_port = 1883
self.m_keepAlive = 60
self.m_cleanSession = True
self.m_protocolVersion = MqttClient.MQTT_3_1
self.m_state = MqttClient.Disconnected
self.m_client = mqtt.Client(clean_session=self.m_cleanSession,
protocol=self.protocolVersion)
self.m_client.on_connect = self.on_connect
self.m_client.on_message = self.on_message
self.m_client.on_disconnect = self.on_disconnect
@QtCore.pyqtProperty(int, notify=stateChanged)
def state(self):
return self.m_state
@state.setter
def state(self, state):
if self.m_state == state: return
self.m_state = state
self.stateChanged.emit(state)
@QtCore.pyqtProperty(str, notify=hostnameChanged)
def hostname(self):
return self.m_hostname
@hostname.setter
def hostname(self, hostname):
if self.m_hostname == hostname: return
self.m_hostname = hostname
self.hostnameChanged.emit(hostname)
@QtCore.pyqtProperty(int, notify=portChanged)
def port(self):
return self.m_port
@port.setter
def port(self, port):
if self.m_port == port: return
self.m_port = port
self.portChanged.emit(port)
@QtCore.pyqtProperty(int, notify=keepAliveChanged)
def keepAlive(self):
return self.m_keepAlive
@keepAlive.setter
def keepAlive(self, keepAlive):
if self.m_keepAlive == keepAlive: return
self.m_keepAlive = keepAlive
self.keepAliveChanged.emit(keepAlive)
@QtCore.pyqtProperty(bool, notify=cleanSessionChanged)
def cleanSession(self):
return self.m_cleanSession
@cleanSession.setter
def cleanSession(self, cleanSession):
if self.m_cleanSession == cleanSession: return
self.m_cleanSession = cleanSession
self.cleanSessionChanged.emit(cleanSession)
@QtCore.pyqtProperty(int, notify=protocolVersionChanged)
def protocolVersion(self):
return self.m_protocolVersion
@protocolVersion.setter
def protocolVersion(self, protocolVersion):
if self.m_protocolVersion == protocolVersion: return
if protocolVersion in (MqttClient.MQTT_3_1, MQTT_3_1_1):
self.m_protocolVersion = protocolVersion
self.protocolVersionChanged.emit(protocolVersion)
#################################################################
@QtCore.pyqtSlot()
def connectToHost(self):
if self.m_hostname:
self.m_client.connect(self.m_hostname,
port=self.port,
keepalive=self.keepAlive)
self.state = MqttClient.Connecting
self.m_client.loop_start()
@QtCore.pyqtSlot()
def disconnectFromHost(self):
self.m_client.disconnect()
def subscribe(self, path):
if self.state == MqttClient.Connected:
self.m_client.subscribe(path)
#################################################################
# callbacks
def on_message(self, mqttc, obj, msg):
mstr = msg.payload.decode("ascii")
# print("on_message", mstr, obj, mqttc)
self.messageSignal.emit(mstr)
def on_connect(self, *args):
# print("on_connect", args)
self.state = MqttClient.Connected
self.connected.emit()
def on_disconnect(self, *args):
# print("on_disconnect", args)
self.state = MqttClient.Disconnected
self.disconnected.emit()
class Widget(QtWidgets.QWidget):
def __init__(self, parent=None):
super(Widget, self).__init__(parent)
lay = QtWidgets.QVBoxLayout(self)
self.lcd_number = QtWidgets.QLCDNumber()
lay.addWidget(self.lcd_number)
self.client = MqttClient(self)
self.client.stateChanged.connect(self.on_stateChanged)
self.client.messageSignal.connect(self.on_messageSignal)
self.client.hostname = "broker.hivemq.com"
self.client.connectToHost()
@QtCore.pyqtSlot(int)
def on_stateChanged(self, state):
if state == MqttClient.Connected:
print(state)
self.client.subscribe("shok2")
@QtCore.pyqtSlot(str)
def on_messageSignal(self, msg):
try:
val = float(msg)
self.lcd_number.display(val)
except ValueError:
print("error: Not is number")
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
w = Widget()
w.show()
sys.exit(app.exec_())
答案 1 :(得分：0)
是否必须创建方法on_connect而不使用运行on_connect的subscribe方法。
def on_connect(self, client, userdata, flags, rc):
print "Connected", rc
client.subscribe("shok2")
def run(self):
msg = subscribe.simple("shok2", hostname="broker.hivemq.com")
print("%s %s" % (msg.topic, msg.payload))
mqttc = mqtt.Client()
mqttc.on_subscribe = self.on_subscribe
mqttc.on_message = self.on_message
mqttc.on_connect = on_connect
mqttc.connect("broker.hivemq.com")
mqttc.loop_forever()