将变量从 MQTT 传递到 Kivy答案

【问题标题】：Pass Variables from MQTT to Kivy将变量从 MQTT 传递到 Kivy
【发布时间】：2018-09-23 11:12:12
【问题描述】：

我尝试使用导航抽屉将值从 MQTT 传递到 Kivy 仪表板。

有人可以提示我如何更改变量吗？这是我的示例代码。 MQTT 正在工作。我使用 Python 3.6.6 和 1.10.1。

mainmenu.py

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.garden.navigationdrawer import NavigationDrawer
from kivy.properties import StringProperty
import paho.mqtt.client as mqtt

class Drawer(NavigationDrawer):
    vartext1 = StringProperty("Button")
    vartext2 = StringProperty("Text")

class MainMenuApp(App):
    def build(self):
        return Drawer()

    def on_start(self):
        topic = "kivy/#"

        def onConnect(client, userdata, flags, rc):
            mqttc.subscribe(topic, 0)

        def onMessage(client, userdata, msg):
            msg.payload = msg.payload.decode("utf-8")
            print ("[INFO   ] [MQTT        ] topic: " + msg.topic +" msg: "+ msg.payload)
            if msg.topic == "kivy/button":
                vartext1 = msg.payload

            if msg.topic == "kivy/text":
                vartext2 = msg.payload

        mqttc = mqtt.Client(client_id="kivy-client", clean_session=True)
        mqttc.on_connect      = onConnect 
        mqttc.on_message      = onMessage
        mqttc.connect("10.0.0.104", 1883, keepalive=60, bind_address="")
        mqttc.loop_start() # start loop to process callbacks! (new thread!)

if __name__ == "__main__":
    MainMenuApp().run()

mainmenu.kv

<Drawer>:
    # Side panel
    BoxLayout:
        padding: 30
        Button:
            text: root.vartext1
    # Main panel
    BoxLayout:
        padding: 30
        Label:
            text: root.vartext2

【问题讨论】：

什么是toggle_state？请提供minimal reproducible example
点击button2，左侧弹出导航菜单。
我从帖子中删除了不必要的部分。
你能接受答案吗？

标签： python kivy navigation-drawer mqtt kivy-language

【解决方案1】：

您可以像这样将“self”参数传递给 mqtt.Client 构造函数：

parameters = {'self': self}
mqttc = mqtt.Client(client_id="kivy-client", clean_session=True, userdata = parameters)

现在在 onMessage 过程中，您可以访问该参数：

userdata['self'].vartext1 = msg.payload

所以你的 mainmenu.py 文件应该是这样的：

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.garden.navigationdrawer import NavigationDrawer
from kivy.properties import StringProperty
import paho.mqtt.client as mqtt

class Drawer(NavigationDrawer):
    vartext1 = StringProperty("Button")
    vartext2 = StringProperty("Text")

class MainMenuApp(App):
    def build(self):
        return Drawer()

    def on_start(self):
        topic = "kivy/#"

        def onConnect(client, userdata, flags, rc):
            mqttc.subscribe(topic, 0)

        def onMessage(client, userdata, msg):
            msg.payload = msg.payload.decode("utf-8")
            print ("[INFO   ] [MQTT        ] topic: " + msg.topic +" msg: "+ msg.payload)
            if msg.topic == "kivy/button":
                userdata['self'].vartext1 = msg.payload

            if msg.topic == "kivy/text":
                userdata['self'].vartext2 = msg.payload

        parameters = {'self': self}
        mqttc = mqtt.Client(client_id="kivy-client", clean_session=True, userdata = parameters)
        mqttc.on_connect      = onConnect 
        mqttc.on_message      = onMessage
        mqttc.connect("10.0.0.104", 1883, keepalive=60, bind_address="")
        mqttc.loop_start() # start loop to process callbacks! (new thread!)

if __name__ == "__main__":
    MainMenuApp().run()

【讨论】：

【解决方案2】：

认为您的问题中缺少.root 对应的userdata['self']。

至少对我来说，当我进行以下更改时它起作用了。

替换

userdata['self'].vartext2 = msg.payload

到

userdata['self'].root.vartext2 = msg.payload

【讨论】：