Properly instantiate classes with Tkinter

Question

My aim is to load a new "arrow" image every time the user presses the shift button. I thought, that I could make a class for the arrow so I can create a new instance for them where each instance has their own coordinates and so on. But obviously I did that wrong. I tried to make a list for the instances so I can iterate of it and then use the moveArrow method in each instance. I just got 5 entries because I want a limit of 5 arrows at the time. I hope this code doesn't give you eyecancer or something like that :P I am a newb and I am sorry, if the code is really bad or the approach on how to handle my problem. Thank you for your help :)

#!/usr/bin/python

from Tkinter import *
from PIL import ImageTk, Image


class frameApp(Frame):
        def __init__(self, master=None):
                Frame.__init__(self, master, height = 400, width = 400)
                self.charImg = ImageTk.PhotoImage(Image.open("Archer.gif"))
                self.arrowImage = ImageTk.PhotoImage(Image.open("arrow.gif"))
                self.charLabel = Label(self, image = self.charImg) #Loading character label
                self.charLabel.pack()
                self.arrow = Label(self, image = self.arrowImage)
                self.arrow.pack()
                self.shift = False
                self.down = False
                self.right = False
                self.left = False
                self.up = False
                self.x_coord = 200
                self.y_coord = 200
                self.pack_propagate(0)
                self.pack()
                self.arrowList = ["Inst1", "Inst2", "Inst3", "Inst4", "Inst5"]
                self.counter = -1
        def moveableImage(self):
                self.charLabel.place(y=self.y_coord, x=self.x_coord)
        def createArrow(self):
                self.arrowList[counter] = arrow()
        def moveArrow(self):
                for arrowList in self.arrowList:
                        arrowList.moveArrow

        def keyPressed(self, event):
                if event.keysym == 'Down':
                        self.down = True
                elif event.keysym == 'Right':
                        self.right = True
                elif event.keysym == 'Left':
                        self.left = True
                elif event.keysym == 'Up':
                        self.up = True
                elif event.keysym == 'Shift_L':
                        self.shift = True
        def keyReleased(self, event):
                if event.keysym == 'Down':
                        self.down = False
                elif event.keysym == 'Right':
                        self.right = False
                elif event.keysym == 'Left':
                        self.left = False
                elif event.keysym == 'Up':
                        self.up = False
                elif event.keysym == 'Shift_L':
                        self.shift = False
        def task(self):
                if self.down and self.y_coord < 360:
                        self.y_coord = self.y_coord + 10
                elif self.right and self.x_coord < 370:
                        self.x_coord = self.x_coord + 10
                elif self.left and self.x_coord > 10:
                        self.x_coord = self.x_coord - 10
                elif self.up and self.y_coord > 10:
                        self.y_coord = self.y_coord - 10
                elif self.shift:
                        self.counter += 1
                        self.createArrow()
                root.after(20,self.task)
                root.after(20,self.moveArrow)
                self.moveableImage()

class arrow(object):
        def __init__(self):
                self.x_coordArrow = app.x_coord
                self.y_coordArrow = app.y_coord
        def moveArrow(self):
                self.x_coordArrow = self.x_coordArrow + 20

root = Tk()
root.title("Frametitel")
app = frameApp(master=root)
root.bind_all('<Key>', app.keyPressed)
root.bind_all('<KeyRelease>', app.keyReleased)
root.after(20, app.task)
app.mainloop()

atlasologist · Accepted Answer · 2014-04-08 15:41:40Z

1

You have several options to handle this. Making a new class to call up multiple instances of arrow() is probably the way to go.

I'd make a class for the application window, which you have, but strip all the unnecessary stuff from it that should be in the Arrow class. Then, make the Arrow class a subclass of a Tkinter widget, like a Frame, and have it handle its methods.

Here's a very simplified version of this:

from Tkinter import *
from random import randint

class App(Frame):
    def __init__(self, master=None):
        Frame.__init__(self, master, height=400, width=400)
        self.master = master
        self.master.bind('<Shift_L>', self.createArrow)

    def createArrow(self, event):
        #this is the only arrow method in this class. It waits for the Shift event,
        #then makes a new instance of Arrow and calls Arrow's method to get it moving
        self.arrow = Arrow(self)
        self.arrow.moveArrow(self.arrow, randint(0,400), randint(0,400))

class Arrow(Frame):
    def __init__(self, master):
        Frame.__init__(self, master)    #This makes the frame,
        Label(self, text='===>').pack() #and puts a Label (the graphic) inside it

    def moveArrow(self, arrow, xCoord, yCoord):
        #the move arrow method - arguments are the arrow instance and the x,y coords
        arrow.place_forget()            #un-place the instance
        arrow.place(x=xCoord, y=yCoord) #replace with new x,y
        self.after(500, lambda: self.moveArrow(arrow, xCoord+1, yCoord)) #repeat, changing x

root = Tk()
app = App(root).pack()
root.mainloop()

answered Apr 8, 2014 at 15:41

atlasologist

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2 Comments

BoJack Horseman Over a year ago

Why does your moveArrow method not give out a maximum recursion error ? You are calling self.moveArrow(arrow, xCoord+15, yCoord) inside moveArrow() method. Shouldn't you have an endless recursion with no break at any stage ?

atlasologist Over a year ago

Take a look at my answer on your other question dealing with this. You're calling self.after in a way that breaks the code.

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