運行時Tkinter窗口空白

Question

當我運行我的tkinter代碼來測量Adafruit的溫度。當我運行我的代碼時，tkinter會打開一個窗口，但窗口上不會顯示任何內容。我之前使用過tkinter，而且我已經有了應該出現的東西，但不是在這個特定的代碼中。

#!/usr/bin/python 
# -*- coding: latin-1 -*- 

import Adafruit_DHT as dht 
import time 
from Tkinter import * 

root = Tk() 
k= StringVar() 
num = 1 
thelabel = Label(root, textvariable=k) 
thelabel.pack 

def READ(): 
    h,t = dht.read_retry(dht.DHT22, 4) 
    newtext = "Temp=%s*C Humidity=%s" %(t,h) 
    k.set(str(newtext)) 
    print newtext #I added this line to make sure that newtext actually had the values I wanted 

def read30seconds(): 
    READ() 
    root.after(30000, read30seconds) 

read30seconds() 
root.mainloop() 

爲了闡明在READ中的打印行確實運行了30秒。

Answer 1

這是因爲您沒有將它打包在窗口中，而是將它打印在python shell中。

你應該替換print newtext有：

w = Label(root, text=newtext) 
w.pack() 

工作的代碼應該是這樣的：

#!/usr/bin/python 
# -*- coding: latin-1 -*- 

import Adafruit_DHT as dht 
import time 
from Tkinter import * 

root = Tk() 
k= StringVar() 
num = 1 
thelabel = Label(root, textvariable=k) 
thelabel.pack 

def READ(): 
    h,t = dht.read_retry(dht.DHT22, 4) 
    newtext = "Temp=%s*C Humidity=%s" %(t,h) 
    k.set(str(newtext)) 
    w = Label(root, text=newtext) 
    w.pack() 


def read30seconds(): 
    READ() 
    root.after(30000, read30seconds) 

read30seconds() 
root.mainloop() 

注意，這是圖形來講一個非常基本的代碼。 瞭解更多有關此主題的此次訪問tkinter label tutorial 和了解更多關於Tkinter的本身，如果你想在標籤被覆蓋每次它被刷新，你應該使用destroy()方法刪除，然後更換標籤訪問該introduction to tkinter

像這樣：

#!/usr/bin/python 
# -*- coding: latin-1 -*- 

import Adafruit_DHT as dht 
import time 
from Tkinter import * 

root = Tk() 
k= StringVar() 
num = 1 
thelabel = Label(root, textvariable=k) 
thelabel.pack 

def READ(): 
    global w 
    h,t = dht.read_retry(dht.DHT22, 4) 
    newtext = "Temp=%s*C Humidity=%s" %(t,h) 
    k.set(str(newtext)) 
    print newtext #I added this line to make sure that newtext actually had the values I wanted 

def read30seconds(): 
    READ() 
    try: w.destroy() 
    except: pass 
    root.after(30000, read30seconds) 

read30seconds() 
root.mainloop()