Tkinter buttons not running commands

Question

Trying to create a simple paint application, and i have a button which when pressed i expect to clear the canvas so a new drawing can be started.

I have buttons being rendered in the tkinter interface, and i have added the drawing_area.delete('all') equivalent of canvas.delete('all') command to my button, but when i draw on the canvas and click the button nothing appears to happen.

Not really sure where i'm going wrong here, would be awesome if someone could help me out, i've put the code for the application below.

from tkinter import *
import tkinter.font
from PIL import Image, ImageTk

class PaintApp:

    # Stores current drawing tool used
    drawing_tool = "pencil"

    # Tracks whether left mouse is down
    left_but = "up"

    # x and y positions for drawing with pencil
    x_pos, y_pos = None, None


    # ---------- CATCH MOUSE UP ----------

    def left_but_down(self, event=None):
        self.left_but = "down"

        # Set x & y when mouse is clicked
        self.x1_line_pt = event.x
        self.y1_line_pt = event.y

    # ---------- CATCH MOUSE UP ----------

    def left_but_up(self, event=None):
        self.left_but = "up"

        # Reset the line
        self.x_pos = None
        self.y_pos = None

        # Set x & y when mouse is released
        self.x2_line_pt = event.x
        self.y2_line_pt = event.y

    # ---------- CATCH MOUSE MOVEMENT ----------

    def motion(self, event=None):

        if self.drawing_tool == "pencil":
            self.pencil_draw(event)

    # ---------- DRAW PENCIL ----------

    def pencil_draw(self, event=None):
        if self.left_but == "down":

            # Make sure x and y have a value
            if self.x_pos is not None and self.y_pos is not None:
                event.widget.create_line(self.x_pos, self.y_pos, event.x, event.y, smooth=TRUE)

            self.x_pos = event.x
            self.y_pos = event.y   

    def __init__(self, root):

        # Add buttons for Finishing and Getting a new Word combo

        drawing_area = Canvas(root, bd=2, highlightthickness=1, relief='ridge')
        drawing_area.pack(side = LEFT, fill="both", expand=True)
        drawing_area.bind("<Motion>", self.motion)
        drawing_area.bind("<ButtonPress-1>", self.left_but_down)
        drawing_area.bind("<ButtonRelease-1>", self.left_but_up)

        toolbar = Frame(root,bd=1,relief = RAISED)
        clearcanvas_img = Image.open("clearcanvas.png")
        clearcanvas_icon = ImageTk.PhotoImage(clearcanvas_img)
        clearcanvas_button = Button(toolbar, image=clearcanvas_icon, command = drawing_area.delete('all'))
        clearcanvas_button.image = clearcanvas_icon
        clearcanvas_button.pack (side = LEFT, padx=2, pady=2)
        toolbar.pack(side = TOP, fill= X)

root = Tk()
paint_app = PaintApp(root)
root.mainloop()

You should use `command=lambda: drawing_area.delete('all')`. Your code just assign `command` the result of `drawing_area.delete('all')`. — acw1668, Dec 29 '19 at 15:06

DaniyalAhmadSE · Accepted Answer · 2019-12-29T15:17:23.403

0

using command=lambda: drawing_area.delete('all') will work. without lambda it just calls the function there. But you need it to be called only when the button is clicked.

edited Dec 29 '19 at 15:17

answered Dec 29 '19 at 15:13

DaniyalAhmadSE

807
11
20

Without ```lambda``` it just calls the function there. But you need it to be called only when the button is clicked. – DaniyalAhmadSE Dec 29 '19 at 15:19

Tkinter buttons not running commands

1 Answers1