如何使tkinter画布更新？

Question

我在tkinter画布中编写了一个条形图，它从列表中获取数据。但是，当我更新列表时，条形图不会更新。我怎样才能解决这个问题

我的代码如下所示：

import tkinter as tk
import random

data = [20, 15, 10, 7, 5, 4, 3, 2, 1, 1, 0]

root = tk.Tk()
root.title("Bar Graph")

c_width = 600 # Define it's width
c_height = 400  # Define it's height
c = tk.Canvas(root, width=c_width, height=c_height, bg='white')
c.pack()

# The variables below size the bar graph
y_stretch = 15  # The highest y = max_data_value * y_stretch
y_gap = 20  # The gap between lower canvas edge and x axis
x_stretch = 10  # Stretch x wide enough to fit the variables
x_width = 20  # The width of the x-axis
x_gap = 20  # The gap between left canvas edge and y axis

# A quick for loop to calculate the rectangle
for x, y in enumerate(data):

    # coordinates of each bar

    # Bottom left coordinate
    x0 = x * x_stretch + x * x_width + x_gap

    # Top left coordinates
    y0 = c_height - (y * y_stretch + y_gap)

    # Bottom right coordinates
    x1 = x * x_stretch + x * x_width + x_width + x_gap

    # Top right coordinates
    y1 = c_height - y_gap

    # Draw the bar
    c.create_rectangle(x0, y0, x1, y1, fill="red")

    # Put the y value above the bar
    c.create_text(x0 + 2, y0, anchor=tk.SW, text=str(y))

root.mainloop()

def update():
    count = 0
    while count < 5:
         barChartData.append(random.randint(1, 11))
         count = count + 1
    update()
update()

我怎样才能解决这个问题

Answer 1

无论何时更改数字，都需要删除旧图形并创建新图形

您应该通过移动代码将条形图绘制到函数中来实现这一点

def draw_barchart(data):
    c.delete("all")
    for x, y in enumerate(data):
        x0 = x * x_stretch + x * x_width + x_gap
        y0 = c_height - (y * y_stretch + y_gap)
        x1 = x * x_stretch + x * x_width + x_width + x_gap
        y1 = c_height - y_gap
        c.create_rectangle(x0, y0, x1, y1, fill="red")
        c.create_text(x0 + 2, y0, anchor=tk.SW, text=str(y))

然后，您可以在数据更改时调用它，传入新数据

但是，您的代码还有其他问题。您需要在程序的最后调用mainloop()，因为它在窗口被破坏之前不会返回

您还需要使用after定期更新数据，或者调用tkinter的update函数来允许窗口重新绘制自身

下面是如何编写代码的底部，以便每五秒钟添加数据并重新绘制图形：

def update():
    count = 0
    for i in range(5):
        data.append(random.randint(1, 11))
    c.delete("all")
    draw_barchart(data)
    root.after(5000, update)

update()

root.mainloop()