"Python Tkinter 变量标签不更新"

Question

我正在尝试使我的标签上的变量更新，但是遇到了一个问题，即按钮的功能通过将温度设置为0.5摄氏度来工作，但是温度和所需温度的标签不会随之改变。在

我在python3.6中工作

这是我的密码，我想知道是否有人可以帮助我？在

import os
import glob
import time
import RPi.GPIO as GPIO
from datetime import datetime


#Set gpio's
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(17,GPIO.OUT)#RED
GPIO.setup(22,GPIO.OUT)#GREEN
GPIO.setup(27,GPIO.OUT)#BLUE


#grab temp probe information
os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

base_dir = '/sys/bus/w1/devices/'
device_folder = glob.glob(base_dir + '28*')[0]
device_file = device_folder + '/w1_slave'


# Read temperature from device

def read_temp_raw():
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines

def read_temp():
    lines=read_temp_raw()
    while lines[0].strip()[-3:] != 'YES':
        time.sleep(0.1)
        lines = read_temp_raw()
    equals_pos = lines[1].find('t=')
    if equals_pos != -1:
        temp_string = lines[1][equals_pos+2:]
        temp_c = float(temp_string) / 1000
        #temp_f = temp_c * 9.0 / 5.0 + 32.0
        return temp_c#, temp_f


temp = read_temp()
desiredtemp = 17
deg = u'\xb0'#utf code for degree


def increase():
    global desiredtemp
    desiredtemp = desiredtemp + 0.5
    print(desiredtemp)

def decrease():
    global desiredtemp
    desiredtemp = desiredtemp - 0.5
    print(desiredtemp)


#Tkinter start

from tkinter import *
root = Tk()
#code to add widgets will go here....

topFrame = Frame(root)
topFrame.pack(side=TOP)

middleFrame = Frame(root)
middleFrame.pack()

bottomFrame = Frame(root)
bottomFrame.pack(side=BOTTOM)

#Set buttons
button1 = Button(bottomFrame, text="Increase (0.5"+ deg +"C)", fg="black", command=increase)
button2 = Button(bottomFrame, text="Decrease (0.5"+ deg +"C)", fg="black", command=decrease)


#use to put buttons on screen
button1.pack(side=LEFT)
button2.pack(side=LEFT)


#Set labels
label1 = Label(topFrame, text="Desired Temp = ", fg="black")
label2 = Label(middleFrame, text="Actual Temp = ", fg="black")
label3 = Label(topFrame, text=desiredtemp, fg="black")
label4 = Label(middleFrame, text=temp, fg="black")


#use to put labels on screen
label1.pack(side=LEFT)
label2.pack(side=LEFT)
label3.pack(side=LEFT)
label4.pack(side=LEFT)



root.mainloop()

#Tkinter End


# Open file to be logged

file = open("/home/pi/Desktop/Templog.csv", "a")

if os.stat("/home/pi/Desktop/Templog.csv").st_size == 0:
    file.write("Date, Time, TemperatureSensor1\n")




# Continuous print loop
while True:
    print(read_temp())
    if(read_temp()<desiredtemp):
       GPIO.output(17,GPIO.LOW)
       GPIO.output(22,GPIO.HIGH)

    else:
       GPIO.output(17,GPIO.HIGH)
       GPIO.output(22,GPIO.LOW)

    now = datetime.now()
    file.write(str(now.day)+"-"+str(now.month)+"-"+str(now.year)+","+str(now.hour)+":"+str(now.minute)+":"+str(now.second)+","+str(read_temp())+"\n")
    file.flush()
    time.sleep(1)

Answer 1

您可以使用StringVar将字符串变量与Label小部件相关联。您将StringVar作为textvariable关键字参数传递给Label，并且在每个按钮回调中，只需使用其set方法更新temperature和StringVar的值。在

扩展您自己的代码的示例：

import os
import glob
import time

from datetime import datetime
from tkinter import *

temp = 18
desiredtemp = 17
deg = u'\xb0'    # utf code for degree


def increase():
    global desiredtemp
    desiredtemp += 0.5
    tmpstr.set("%s" % desiredtemp)


def decrease():
    global desiredtemp
    desiredtemp -= 0.5
    tmpstr.set("%s" % desiredtemp)

root = Tk()

topFrame = Frame(root)
topFrame.pack(side=TOP)

middleFrame = Frame(root)
middleFrame.pack()

bottomFrame = Frame(root)
bottomFrame.pack(side=BOTTOM)

button1 = Button(bottomFrame, text="Increase (0.5"+ deg +"C)", fg="black", command=increase)
button2 = Button(bottomFrame, text="Decrease (0.5"+ deg +"C)", fg="black", command=decrease)

button1.pack(side=LEFT)
button2.pack(side=LEFT)

tmpstr = StringVar(value="%s" % desiredtemp)

label1 = Label(topFrame, text="Desired Temp = ", fg="black")
label2 = Label(middleFrame, text="Actual Temp = ", fg="black")
label3 = Label(topFrame, textvariable=tmpstr, fg="black")
label4 = Label(middleFrame, text=temp, fg="black")

label1.pack(side=LEFT)
label2.pack(side=LEFT)
label3.pack(side=LEFT)
label4.pack(side=LEFT)

root.mainloop()

注意，global关键字的使用通常被认为是code smell，这应该让您考虑将所有这些元素放入一个类中。在