在tkinter UI中绘制两个对象之间的线

Question

多亏了Tkinter UI中拖放对象的大量帮助，我可以画出三个可拖动的正方形。

现在我试图在每个方块之间画3条线，但我找不到启用它的方法

from tkinter import *
window = Tk()
window.state('zoomed')
window.configure(bg = 'white')
def drag(event):
new_x = event.x_root - window.winfo_rootx()
new_y = event.y_root - window.winfo_rooty()
event.widget.place(x=new_x, y=new_y,anchor=CENTER)
card = Canvas(window, width=10, height=10, bg='red1')
card.place(x=300, y=600,anchor=CENTER)
card.bind("<B1-Motion>", drag)
another_card = Canvas(window, width=10, height=10, bg='red2')
another_card.place(x=600, y=600,anchor=CENTER)
another_card.bind("<B1-Motion>", drag)
third_card = Canvas(window, width=10, height=10, bg='red3')
third_card.place(x=600, y=600,anchor=CENTER)
third_card.bind("<B1-Motion>", drag)
def line(x1, y1, x2, y2):
print(x1, y1, x2, y2)
Canvas.create_line(x1, y1, x2, y2, fill="green")
coor_1 = canvas.coords(card)
coor_2 = canvas.coords(another_card)
line(coor_1[0],coor_1[1],coor_1[0],coor_2[1])
window.mainloop()

它没有起作用，我认为它也不会起作用，因为这段代码没有捕捉到拖动对象所发生的变化，但我无法猜测如何编码，因为我不了解事件函数是如何完全工作的。我应该如何为它编写代码？

Answer 1

用于自学：

import tkinter as tk
window = tk.Tk()
window.state('zoomed')
class DragAndDropArea(tk.Canvas):
def __init__(self,master, **kwargs):
tk.Canvas.__init__(self,master, **kwargs)
self.active = None
card_I = self.draw_card(300,600, 100,100, 'red1')
card_II = self.draw_card(600,600, 100,100, 'red2')
card_III = self.draw_card(400,400, 100,100, 'red3')
self.bind_tention(card_I,card_III)
self.bind_tention(card_I,card_II)
self.bind_tention(card_III,card_II)
self.bind('<ButtonPress-1>', self.get_item)
self.bind('<B1-Motion>',self.move_active)
self.bind('<ButtonRelease-1>', self.set_none)
def set_none(self,event):
self.active = None
def get_item(self,event):
try:
item =  self.find_withtag('current')
self.active = item[0]
except IndexError:
print('no item was clicked')
def move_active(self,event):
if self.active != None:
coords = self.coords(self.active)
width = coords[2] - coords[0] #x2-x1
height= coords[1] - coords[3] #y1-y2
position = coords[0],coords[1]#x1,y1
x1 = event.x - width/2
y1 = event.y - height/2
x2 = event.x + width/2
y2 = event.y + height/2

self.coords(self.active, x1,y1, x2,y2)
try:
self.update_tention(self.active)
except IndexError:
print('no tentions found')
def update_tention(self, tag):
tentions = self.find_withtag(f'card {tag}')
for tention in tentions:
bounded_cards = self.gettags(tention)
card = bounded_cards[0].split()[-1]
card2= bounded_cards[1].split()[-1]
x1,y1 = self.get_mid_point(card)
x2,y2 = self.get_mid_point(card2)
self.coords(tention, x1,y1, x2,y2)
self.lower(tention)
def draw_card(self, x,y, width,height, color):
x1,y1 = x,y
x2,y2 = x+width,y+height
reference = self.create_rectangle(x1,y1,x2,y2,
fill = color)
return reference
def bind_tention(self, card, another_card):
x1,y1 = self.get_mid_point(card)
x2,y2 = self.get_mid_point(another_card)
tag_I = f'card {card}'
tag_II= f'card {another_card}'

reference = self.create_line(x1,y1,x2,y2, fill='green',
tags=(tag_I,tag_II))
self.lower(reference)
def get_mid_point(self, card):
coords = self.coords(card)
width = coords[2] - coords[0] #x2-x1
height= coords[1] - coords[3] #y1-y2
position = coords[0],coords[1]#x1,y1
mid_x = position[0] + width/2
mid_y = position[1] - height/2
return mid_x,mid_y

area = DragAndDropArea(window, bg='white')
area.pack(fill='both',expand=1)
window.mainloop()