在mainloop（）中更新Tkinter畫布

Question

我正在嘗試在Tkinter中創建一個簡單的冒泡排序可視化，但是我不知道如何更新畫布/刷新。

from tkinter import *
import random
height, width = 350,600
randomLines = []
master = Tk()
w = Canvas(master,width=width,height=height)
w.pack()

def drawRandomLines():
    w.delete("all")
    for i in range(width):
        w.create_line(i,0,i,randomLines[i])

def bubbleSort():
    for passnum in range(len(randomLines)-1,0,-1):
        for i in range(passnum):
            if randomLines[i]>randomLines[i+1]:
                temp = randomLines[i]
                randomLines[i] = randomLines[i+1]
                randomLines[i+1] = temp

for i in range(width):
    rnd = random.randint(0,width)
    randomLines.append(rnd)
drawRandomLines()
bubbleSort()
mainloop()

如果我在bubbleSort（）循環內使用drawRandomLines（），它將保留該窗口並在排序之前不會顯示畫布

Answer 1

您將要使用after()來管理不會影響主循環的更新循環。 通過使用after()我們可以隨時間創建可視更新。 我們將需要一個跟蹤變量來管理循環上​​的索引，並需要一個用於跟蹤程序的全局語句。

例：

from tkinter import *
import random
height, width = 350, 600
randomLines = []
master = Tk()
tracker = 0
w = Canvas(master, width=width, height=height)
w.pack()

def drawRandomLines():
    global tracker
    if tracker <= width:
        w.create_line(tracker, 0, tracker, randomLines[tracker])
        tracker += 1
        master.after(10, drawRandomLines)

def bubbleSort():
    for passnum in range(len(randomLines)-1, 0, -1):
        for i in range(passnum):
            if randomLines[i] > randomLines[i+1]:
                temp = randomLines[i]
                randomLines[i] = randomLines[i+1]
                randomLines[i+1] = temp

for i in range(width):
    rnd = random.randint(0, width)
    randomLines.append(rnd)
drawRandomLines()
bubbleSort()
mainloop()

Answer 2

在完成重要任務的隊列之前，Tkinter不會更新窗口。 因此，如果要每次迭代更新，則必須強制執行。 嘗試這個：

def drawRandomLines():
    w.delete("all")
    for i in range(width):
        w.create_line(i,0,i,randomLines[i])
    w.update()   # Force canvas update

Answer 3

您可以使用after()替換bubbleSort()的外部for循環，並在drawRandomLines()內部調用bubbleSort() ：

from tkinter import *
import random

height, width = 350, 600
thickness = 5

# create the random lines
randomLines = [random.randint(1, height-1) for i in range(0, width, thickness)]

master = Tk()
w = Canvas(master, width=width, height=height)
w.pack()

def drawRandomLines():
    w.delete("all")
    for i in range(len(randomLines)):
        x = i * thickness
        # use bars for more clearly presentation
        w.create_rectangle(x, height, x+thickness, height-randomLines[i], fill='red')

def bubbleSort(passnum):
    for i in range(passnum):
        if randomLines[i] > randomLines[i+1]:
            randomLines[i], randomLines[i+1] = randomLines[i+1], randomLines[i]
    drawRandomLines()
    if passnum > 0:
        master.after(20, bubbleSort, passnum-1)
    else:
        w.create_text(50, 50, text='Done!', font=('Arial', 24))

drawRandomLines() # show initial order of lines
bubbleSort(len(randomLines)-1)

master.mainloop()