Posts: 2
Threads: 1
Joined: Dec 2020
Hello all,
With the help of some users in different forums I have get this far, but facing a new challenge in my way to making my first real world GUI, I hope some expert in tkinter can help. Needless to say that I am a novice in Python...
I have made a device with the following structure:
- Presence sensors and controllers for Arduino
Arduino Mega
Raspberry Pi4
Video card
1280x800 OEM screen
What the system should do is: the Arduino is running a firmware to read the presence sensors and determine a position with a set of coordinates (x;y) and prints them through the Serial port (USB) in a line. The Raspberry running my Python code gets the information from the Serial port and breaks the line into 2 coordinates again. Then the program is supposed to paint a red rectangle if the coordinates are within the area defined, corresponding to 4 areas in the background image of the GUI.
I am using Tkinter for this as it looked pretty easy for me to make the main window, put a background image and paint rectangles, but the reality is that I am finding that when I run the functions of painting the rectangles it looks like Tkinter “is not present” somehow (sorry for my lack of knowledge in explaining the issue).
The code is this (and the error below):
from serial import *
from tkinter import *
import time
root = Tk()
root.geometry("1280x800")
root.attributes('-fullscreen',True)
bg = PhotoImage(file = "/home/pi/Pictures/SCREEN2.png")
canvas = Canvas( root, width = 1280, height = 800)
canvas.pack(fill = "both", expand = True)
canvas.create_image( 0, 0, image = bg, anchor = "nw")
serialPort = "/dev/ttyUSB0"
ser = Serial(serialPort, 9600, timeout=0)
ser.flush()
def split_coords(astring):
a, b = astring.split(';')
a = int(a)
b = int(b)
return (a, b)
def paintRectangle1():
canvas.create_rectangle(200, 120, 400, 220, fill='red')
time.sleep(0.3)
def paintRectangle2():
canvas.create_rectangle(600, 120, 800, 220, fill='red')
time.sleep(0.3)
def paintRectangle3():
canvas.create_rectangle(200, 260, 400, 360, fill='red')
time.sleep(0.3)
def paintRectangle4():
canvas.create_rectangle(600, 260, 800, 360, fill='red')
time.sleep(0.3)
root.mainloop()
while True:
if ser.in_waiting> 0:
line = ser.readline().decode('utf-8').rstrip()
x, y = split_coords(line)
print("x:", x, "- y:", y)
if (19 < x < 60) and (20 < y < 40):
print("OK button1")
paintRectangle1()
if (68 < x < 110) and (20< y < 40):
print("OK button2")
paintRectangle2()
if (19 < x < 60) and (45 < y < 80):
print("OK button3")
paintRectangle3()
if (68 < x <110) and (45 < y < 80):
print("OK button4")
paintRectangle4()
#else:
#paint the backgrand image again after the 0.3 seconds defined into the paintRectangle functionThe error that this code throws:
Error: x: 32 - y: 28
OK button1
Traceback (most recent call last):
File "/home/pi/Documents/Touch-GUI-TKInter_4.py", line 52, in <module>
paintRectangle1()
File "/home/pi/Documents/Touch-GUI-TKInter_4.py", line 26, in paintRectangle1
canvas.create_rectangle(200, 120, 400, 220, fill='red')
File "/usr/lib/python3.7/tkinter/__init__.py", line 2501, in create_rectangle
return self._create('rectangle', args, kw)
File "/usr/lib/python3.7/tkinter/__init__.py", line 2480, in _create
*(args + self._options(cnf, kw))))
_tkinter.TclError: invalid command name ".!canvas"
As can be seen, the program goes into the paintRectangle after reading the coordinates, but it does not "understand" the canvas operation.
I really don’t know what I should do to “get the mainframe inside the def statements” to make this work.
Does anyone have an idea of what I am doing wrong? 
Thanks in advance.
Joan.
Posts: 24
Threads: 9
Joined: Mar 2019
the canvas object you created is not visible to the paintRectangle[1-4] methods due to being out of scope of the subject methods, you can either adopt an object oriented approach to the above problem or you can pass an instance of the canvas object when you call the paintRectangle[1-4] methods,
def paintRectangle1(canvas_ref):
canvas_ref.create_rectangle(200, 120, 400, 220, fill='red')
time.sleep(0.3)
def paintRectangle2(canvas_ref):
canvas_ref.create_rectangle(600, 120, 800, 220, fill='red')
time.sleep(0.3)
def paintRectangle3(canvas_ref):
canvas_ref.create_rectangle(200, 260, 400, 360, fill='red')
time.sleep(0.3)
def paintRectangle4(canvas_ref):
canvas_ref.create_rectangle(600, 260, 800, 360, fill='red')
time.sleep(0.3)and you can call the methods like
canvas = Canvas( root, width = 1280, height = 800)
if (19 < x < 60) and (20 < y < 40):
print("OK button1")
paintRectangle1(canvas)
if (68 < x < 110) and (20< y < 40):
print("OK button2")
paintRectangle2(canvas)
if (19 < x < 60) and (45 < y < 80):
print("OK button3")
paintRectangle3(canvas)
if (68 < x <110) and (45 < y < 80):
print("OK button4")
paintRectangle4(canvas)
Ensaimadeta likes this post
Posts: 2
Threads: 1
Joined: Dec 2020
Hello iMuny, thanks for your suggestion.
I have done as you suggested and still no luck... 
This is how it looks now:
from serial import *
from tkinter import *
import time
root = Tk()
root.geometry("1280x800")
root.attributes('-fullscreen',True)
bg = PhotoImage(file = "/home/pi/Pictures/SCREEN2.png")
canvas = Canvas( root, width = 1280, height = 800)
canvas.pack(fill = "both", expand = True)
canvas.create_image( 0, 0, image = bg, anchor = "nw")
serialPort = "/dev/ttyUSB0"
ser = Serial(serialPort, 9600, timeout=0)
ser.flush()
def split_coords(astring):
a, b = astring.split(';')
a = int(a)
b = int(b)
return (a, b)
def paintRectangle1(canvas_ref):
print("entered Rect 1")
canvas_ref.create_rectangle(207, 151, 620, 374, fill='red')
time.sleep(0.3)
def paintRectangle2(canvas_ref):
print("entered Rect 2")
canvas_ref.create_rectangle(600, 120, 800, 220, fill='red')
time.sleep(0.3)
def paintRectangle3(canvas_ref):
print("entered Rect 3")
canvas_ref.create_rectangle(200, 260, 400, 360, fill='red')
time.sleep(0.3)
def paintRectangle4(canvas_ref):
print("entered Rect 4")
canvas_ref.create_rectangle(600, 260, 800, 360, fill='red')
time.sleep(0.3)
root.mainloop()
while True:
if ser.in_waiting> 0:
line = ser.readline().decode('utf-8').rstrip()
x, y = split_coords(line)
print("x:", x, "- y:", y)
canvas = Canvas( root, width = 1280, height = 800)
if (x>19) and (x<60) and (y>20) and (y<40):
print("OK button1")
paintRectangle1(canvas)
if (x>68) and (x<110) and (y>20) and (y<40):
print("OK button2")
paintRectangle2(canvas)
if (x>19) and (x<60) and (y>45) and (y<80):
print("OK button3")
paintRectangle3(canvas)
if (x>68) and (x<110) and (y>45) and (y<80):
print("OK button4")
paintRectangle4(canvas)
'''
else:
canvas.create_image( 0, 0, image = bg, anchor = "nw")
'''and the error...
Error: x: 11 - y: 11
Traceback (most recent call last):
File "/home/pi/Documents/Touch-GUI-TKInter_4.py", line 55, in <module>
canvas = Canvas( root, width = 1280, height = 800)
File "/usr/lib/python3.7/tkinter/__init__.py", line 2405, in __init__
Widget.__init__(self, master, 'canvas', cnf, kw)
File "/usr/lib/python3.7/tkinter/__init__.py", line 2299, in __init__
(widgetName, self._w) + extra + self._options(cnf))
_tkinter.TclError: can't invoke "canvas" command: application has been destroyed
Posts: 6,552
Threads: 19
Joined: Feb 2020
Code located after "root.mainloop()" is not going to execute until you close the root window. But you can't just move your while loop ahead of "root.mainloop()" because that prevents tkinter from running. What you need to do is simultaneously let mainloop() run while processing data from your serial port. There is probably a framework for doing this kind of thing built into your Raspberry Pi libraries. Look at the serial port library for some way to call a function when data is available on the serial port. Failing that, look for some kind of scheduler that will execute a function periodically.
You could always use the ".after" function from tkinter. In the example below I used root.after() in the random_rectangle() function to execute the function 10 times a second while letting mainloop() run at the same time.
import random
from tkinter import *
import time
rectangle = None
root = Tk()
root.geometry("200x200")
canvas = Canvas( root, width = 1280, height = 800)
canvas.pack(fill = "both", expand = True)
canvas.create_image(0, 0, anchor = "nw")
def random_rectangle():
global rectangle
if rectangle is not None:
canvas.delete(rectangle)
x = random.randint(0, 200) // 50 * 50
y = random.randint(0, 200) // 50 * 50
rectangle = canvas.create_rectangle(x, y, x+50, y+50, fill='red')
root.after(100, random_rectangle)
random_rectangle()
root.mainloop()
print('This is not executed until you close the root window')
Posts: 1
Threads: 0
Joined: Dec 2023
(Dec-22-2020, 07:11 PM)Ensaimadeta Wrote: Hello iMuny, thanks for your suggestion.
I have done as you suggested and still no luck...
This is how it looks now:
from serial import *
from tkinter import *
import time
root = Tk()
root.geometry("1280x800")
root.attributes('-fullscreen',True)
bg = PhotoImage(file = "/home/pi/Pictures/SCREEN2.png")
canvas = Canvas( root, width = 1280, height = 800)
canvas.pack(fill = "both", expand = True)
canvas.create_image( 0, 0, image = bg, anchor = "nw")
serialPort = "/dev/ttyUSB0"
ser = Serial(serialPort, 9600, timeout=0)
ser.flush()
def split_coords(astring):
a, b = astring.split(';')
a = int(a)
b = int(b)
return (a, b)
def paintRectangle1(canvas_ref):
print("entered Rect 1")
canvas_ref.create_rectangle(207, 151, 620, 374, fill='red')
time.sleep(0.3)
def paintRectangle2(canvas_ref):
print("entered Rect 2")
canvas_ref.create_rectangle(600, 120, 800, 220, fill='red')
time.sleep(0.3)
def paintRectangle3(canvas_ref):
print("entered Rect 3")
canvas_ref.create_rectangle(200, 260, 400, 360, fill='red')
time.sleep(0.3)
def paintRectangle4(canvas_ref):
print("entered Rect 4")
canvas_ref.create_rectangle(600, 260, 800, 360, fill='red')
time.sleep(0.3)
root.mainloop()
while True:
if ser.in_waiting> 0:
line = ser.readline().decode('utf-8').rstrip()
x, y = split_coords(line)
print("x:", x, "- y:", y)
canvas = Canvas( root, width = 1280, height = 800)
if (x>19) and (x<60) and (y>20) and (y<40):
print("OK button1")
paintRectangle1(canvas)
if (x>68) and (x<110) and (y>20) and (y<40):
print("OK button2")
paintRectangle2(canvas)
if (x>19) and (x<60) and (y>45) and (y<80):
print("OK button3")
paintRectangle3(canvas)
if (x>68) and (x<110) and (y>45) and (y<80):
print("OK button4")
paintRectangle4(canvas)
'''
else:
canvas.create_image( 0, 0, image = bg, anchor = "nw")
'''and the error...
Error: x: 11 - y: 11
Traceback (most recent call last):
File "/home/pi/Documents/Touch-GUI-TKInter_4.py", line 55, in <module>
canvas = Canvas( root, width = 1280, height = 800)
File "/usr/lib/python3.7/tkinter/__init__.py", line 2405, in __init__
Widget.__init__(self, master, 'canvas', cnf, kw)
File "/usr/lib/python3.7/tkinter/__init__.py", line 2299, in __init__
(widgetName, self._w) + extra + self._options(cnf))
_tkinter.TclError: can't invoke "canvas" command: application has been destroyed
same here. did you found the solution
Posts: 6,552
Threads: 19
Joined: Feb 2020
You could use tkinter.after() to periodically run a function that checks for input on the serial port, or you can run the serial port loop in a separate thread.
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