将paho-mqtt与PyQt一起使用

Question

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。当我收到新消息时，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。订阅主题来自仪表板

#!/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_())

Answer 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，至少到现在为止已经实现了所需的功能，在接下来的几天中，我将添加更多的功能。

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_())

基于此答案，我创建了一个库，将paho与PyQt5和PySide2结合使用： https

//github.com/eyllanesc/qtmqtt