試圖根據文本文件更新Tkinter中的行位置

Question

我正在創建一個Tkinter程序，該程序根據保存到文本文件的角度創建一個顯示車輛位置的畫布。我遇到的問題是，程序僅在啓動時讀取文本文件，並且不會繼續檢查。我知道這應該是相當簡單的，但我已經看過很多網站，無法找到一種方法來做到這一點。這裏是我的代碼

  from Tkinter import * 
      import math 
      import time 

      root = Tk() 
      root.geometry("800x480") 
      root.configure(background='darkgrey') 
      content = Frame(root,) 

      #Dimensions of Window 
      w = 800 
      h = 480 

      #Get Angle 
      file_angle = open("current_angle.txt") 
      #read file and remove "/n" from the end of the string 
      string_angle = ((file_angle.read())[:-2]) 
      #Convert string to a number 
      read_angle = float(string_angle) 

      if read_angle > 90 or read_angle <-90: 
       deg_angle = read_angle - 180 

      else: 
       deg_angle = read_angle 

      angle = math.radians(deg_angle) 
      swath_width = w/5 

      if deg_angle > -90 and deg_angle < 90: 
       #Center Line 
       centertopx = (w/2) + ((h/1.5) * math.tan(angle)) 
       centertopy = 0 
       centerbottomx = (w/2) + ((h - (h/1.5)) * math.tan(-1 * angle)) 
       centerbottomy = h 

      if deg_angle == 90 or deg_angle == -90: 
       centertopx = 0 
       centertopy = h/2 
       centerbottomx = w 
       centerbottomy = h/2 

      #Create Guidance Map 
      livemap = Canvas(root, width=w, height=h) 
      #Outline of map 
      livemap.create_rectangle(0,0,w,h, outline="black", width=5, fill="#9E9E9E") 


      #Drawing lines 
      livemap.create_line(centertopx, centertopy, centerbottomx, centerbottomy, fill="red", width=4) 

      #stationary parts of map 
      #Triangle that represents vehicle 
      livemap.create_polygon(
       ((w/2)-(w * 0.04)),((h/1.5)+(h * 0.1)),((w/2)+(w *     0.04)),((h/1.5)+(h * 0.1)),(w/2),(h/1.5), 
       outline="black", fill="darkorange", width=2) 
      livemap.create_line((w/2),((h/1.5)+(h*0.07)),(w/2),(h/1.5),fill="black", width=2) 
      livemap.create_polygon(((w/2)-(w * 0.04)),((h/1.5)+(h * 0.1)),((w/2)+(w * 0.04)),((h/1.5)+(h * 0.1)),(w/2),((h/1.5)+(h*0.07)), 
       outline="black", fill="darkorange", width=2) 

      #Put canvas into window 
      livemap.grid(column=0, row=0, columnspan=4, rowspan=4) 

      root.mainloop() 

Answer 1

使用root.after(miliseconds, function_name)以定期運行功能，將讀取在畫布上再次文件和移動線。

在代碼中，我只創建一行（車輛之前），後來我只更改了行位置。

from Tkinter import * 
import math 
import time 

w = 800 
h = 480 

# --- functions --- 

def update_line(): 

    deg_angle = open("current_angle.txt") 
    deg_angle = deg_angle.read()[:-2] 
    deg_angle = float(deg_angle) 

    if deg_angle > 90 or deg_angle <-90: 
     deg_angle -= 180 

    if deg_angle == 90 or deg_angle == -90: # you need 
     centertopx = 0 
     centertopy = h/2 
     centerbottomx = w 
     centerbottomy = h/2 
    else: # deg_angle > -90 and deg_angle < 90: 

     angle = math.radians(deg_angle) 

     #Center Line 
     centertopx = (w/2) + ((h/1.5)*math.tan(angle)) 
     centertopy = 0 
     centerbottomx = (w/2) + ((h - (h/1.5))*math.tan(-angle)) 
     centerbottomy = h 

    # move line 
    livemap.coords(line, centertopx, centertopy, centerbottomx, centerbottomy) 

    # repeat after 200 ms (0.2s) 
    root.after(200, update_line) 

# --- main --- 

root = Tk() 
root.geometry("800x480") 
root.configure(background='darkgrey') 

content = Frame(root,) 
livemap = Canvas(root, width=w, height=h) 
livemap.create_rectangle(0, 0, w, h, outline="black", width=5, fill="#9E9E9E") 

# create line (without angle) before vehicle 
line = livemap.create_line(w/2, 0, w/2, h, fill="red", width=4) 

#Triangle that represents vehicle 
livemap.create_polygon(
    (w/2)-(w*0.04), (h/1.5)+(h*0.1), 
    (w/2)+(w*0.04), (h/1.5)+(h*0.1), 
    w/2, h/1.5, 
    outline="black", fill="darkorange", width=2) 

livemap.create_line(w/2, (h/1.5)+(h*0.07), w/2, h/1.5, fill="black", width=2) 

livemap.create_polygon(
    (w/2)-(w*0.04), (h/1.5)+(h*0.1), 
    (w/2)+(w*0.04), (h/1.5)+(h*0.1), 
    w/2, (h/1.5)+(h*0.07), 
    outline="black", fill="darkorange", width=2) 

livemap.grid(column=0, row=0, columnspan=4, rowspan=4) 

# update line first time 
update_line() 

root.mainloop()