python - tkinter root.mainloop 与 While True 循环

Question

我正在使用 tkinter 根据我正在读取的电压显示一些标签。但是，它会在一次读取后停止执行。我发现这是由于 root.mainloop()。但我无法修复它。我已经包含了我的代码。 root.mainloop() 正好位于 while True 的末尾。

from Tkinter import *
import spidev
import time
import os
import RPi.GPIO as GPIO
import numpy

GPIO.cleanup()
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7, GPIO.OUT)
GPIO.setup(11, GPIO.OUT)
GPIO.setup(13, GPIO.OUT)
GPIO.setup(15, GPIO.OUT)
GPIO.setup(12, GPIO.OUT)
adcvolt = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
batvolt = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]

root = Tk() #Makes the window
w,h = root.winfo_screenwidth(), root.winfo_screenheight()
root.overrideredirect(1)
root.geometry("%dx%d+0+0"%(w,h))

labelFont = ("times",15 ,"bold", "italic")
labelText1 = StringVar()
labelText2 = StringVar()
labelText3 = StringVar()
labelText4 = StringVar()
labelText5 = StringVar()
labelText6 = StringVar()

labelText1.set("Battery Management System")
label1 = Label(root, textvariable=labelText1, height=3, anchor="center")
label1.config(font=labelFont)
label1.pack()
labelText2.set("Wait")
label2 = Label(root, textvariable=labelText2, height=3, anchor="center")
label2.config(font=labelFont)
label2.pack()
labelText3.set("Wait")
label3 = Label(root, textvariable=labelText3, height=3, anchor="center")
label3.config(font=labelFont)
label3.pack()
labelText4.set("Wait")
label4 = Label(root, textvariable=labelText4, height=3, anchor="center")
label4.config(font=labelFont)
label4.pack()
labelText5.set("Wait")
label5 = Label(root, textvariable=labelText5, height=3, anchor="center")
label5.config(font=labelFont)
label5.pack()
labelText6.set("Wait")
label6 = Label(root, textvariable=labelText6, height=3, anchor="center")
label6.config(font=labelFont)
label6.pack()
#root.wm_title("Window Title") #Makes the title that will appear in the top left
#root.config(background = "#FFFFFF") #sets background color to white


# Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)

# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7
def ReadChannel(channel):
  adc = spi.xfer2([1,(8+channel)<<4,0])
  data = ((adc[1]&3) << 8) + adc[2]
  return data

#Function to select multiplexer channel on 74HCT4067 chip
#Channel must be an integer 0-15
def MuxSelect(muxchannel):
    if muxchannel == 0:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 1:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 2:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 3:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,1)
    elif muxchannel == 4:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 5:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 6:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 7:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,1)
    elif muxchannel == 8:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 9:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 10:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 11:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,1)
    elif muxchannel == 12:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 13:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 14:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 15:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,1)



# Function to convert data to voltage level,
# rounded to specified number of decimal places. 
def ConvertVolts(data,places):
  volts = (data * 3.3) / 1023
  volts = round(volts,places)
  return volts

# Define sensor channels
voltage_channel = 0


# Define delay between readings
delay = 2




while True:
  count = 0

  while count<15:
    MuxSelect(count)

    # Read the voltage sensor data
    voltage_level = ReadChannel(voltage_channel)
    voltage_volts = ConvertVolts(voltage_level,2)
    adcvolt[count] = voltage_volts
    batvolt[count] = adcvolt[count] * 2.842

    #print adcvolt[count]
    #print batvolt[count]
    #print count
    count = count + 1
    #time.sleep(delay)
  labelText2.set('Cell1= '+str(batvolt[0])+'V  Cell2= ' +str(batvolt[1])+'V  Cell3= '+str(batvolt[2]))
  #root.update()
  labelText3.set('Cell4= '+str(batvolt[3])+'V  Cell5= ' +str(batvolt[4])+'V  Cell6= '+str(batvolt[5]))
 # root.update()
  labelText4.set('Cell7= '+str(batvolt[6])+'V  Cell8= ' +str(batvolt[7])+'V  Cell9= '+str(batvolt[8]))
#  root.update()
  labelText5.set('Cell10= '+str(batvolt[9])+'V  Cell11= ' +str(batvolt[10])+'V  Cell12= '+str(batvolt[11]))
#  root.update()
  labelText6.set('Cell13= '+str(batvolt[12])+'V  Cell14= ' +str(batvolt[13])+'V  Cell15= '+str(batvolt[14]))
  root.update()
  print "shit"  

  medianvolt = numpy.median(batvolt)
  maxvolt = max(batvolt)
  minvolt = min(batvolt)
  diff1 = maxvolt-medianvolt
  diff2 = medianvolt-minvolt

  if diff1>0.02 or diff2>0.02:
    GPIO.output (12,1)
    time.sleep(120)
    GPIO.output (12,0)


    # Wait before repeating loop
    time.sleep(delay)

  root.update()

  root.mainloop() #start monitoring and updating the GUI. Nothing below here runs.

Answer 1

tkinter 需要 mainloop() 才能正常工作 - 它使用它一次又一次地调用所有需要的函数 - 即。从系统获取键/鼠标事件，将它们发送到小部件，更新值，并在窗口中(重新)绘制小部件。

在 tkinter 中不要使用永远运行(或运行更长时间)的 while True 因为它会阻塞 mainloop() 在 tkinter 并且它无法更新窗口中的项目，看起来像卡住了。

同样的问题使 sleep() - 它可以阻止 tkinter 中的 mainloop()。

您可以使用 root.after(time_ms, function_name_without_brackets )(在 mainloop() 之前)
延迟运行一些函数 - 所以它可以像 sleep() 一样使用。如果函数将运行相同的 after(...) 那么它将像循环一样工作。这样 tkinter 将有时间更新窗口中的小部件。

---

因此，将 while True 中的所有代码(mainloop() 除外)放入函数中，并使用 after() 调用它。
并使用第二个 after() 代替 sleep()。

import tkinter as tk

master = tk.Tk()

def my_mainloop():
    print "Hello World!"
    master.after(1000, my_mainloop)  # run again after 1000ms (1s)

master.after(1000, my_mainloop) # run first time after 1000ms (1s)

master.mainloop()

---

如果您不能转换 while 循环并使用 after()，那么您可能必须在单独的线程中运行循环。但是 tkinter(与许多其他 GUI 一样)` 不喜欢在第二个线程中工作，并且 GUI 中的所有更改都必须在主线程中进行。