Python Tkinter Canvas 没有出现

Question

你好，我在 python 上使用 Tkinter 包时遇到问题。我想创建一个包含两个主要小部件的 window，其中一个是 canvas，稍后将显示带有单元格的网格。在初始化 canvas 时，我使用 "create_rectangle" 来填充 canvas 所需的对象。此外，当单击一个单元格时（出于测试原因），canvas 应该改变其在矩形区域中的颜色。但是，当最初显示 window 时，一开始看不到任何对象（预期结果只会是白色矩形），只有当单击 canvas 时，该区域才会根据需要更改颜色。在浏览互联网时，我尝试了 pack()- 和 create_rectangle()- 方法顺序的几种变体。这是代码：

from tkinter import *
from tkinter.ttk import *
import cells

GRID_WIDTH = 15
GRID_HEIGHT = 15


class Ui(Frame):
    """ Class to represent the ui of conways game of life"""

    def __init__(self, parent, grid):
        self.parent = parent
        self.grid = grid
        Frame.__init__(self, parent)
        self.__setup()

    def __setup(self):
        """ Method to setup the components of the ui """
        self.parent.title("Conway's game of life")
        self.pack()

        #Setup a frame to hold control components
        frame_cntrl = Frame(self)
        frame_cntrl.pack(side = RIGHT, anchor="n")
        self.__setup_cntrl_components(frame_cntrl)

        #Setup a frame to hold the Grid
        self.canvas = Canvas(self)
        self.canvas.pack(side = LEFT)
        self.__draw_grid()
        self.canvas.bind("<Button-1>", self.__canvas_clicked)


    def __setup_cntrl_components(self, parent):
        """ Method to setup the control elements of the ui"""
        #Setup a label for the generation
        self.lb_generation = Label(parent, text="dummy")
        self.lb_generation.pack(side = TOP)

        #Setup a button for iteration
        self.bt_iteration = Button(parent, text="Iterate")
        self.bt_iteration.pack(side = TOP)



    def __draw_cell(self, x, y):
        """ Draws a cell on the canvas"""
        width, height = self.canvas.winfo_width(), self.canvas.winfo_height()
        color = "black" if self.grid.cell_alive(x, y) else "white"
        x0 = width * x / self.grid.width + 1
        x1 = width * (x + 1) / self.grid.width
        y0 = height * y / self.grid.height + 1
        y1 = height * (y + 1) / self.grid.height
        self.canvas.create_rectangle(x0, y0, x1, y1, width=0, fill=color)

    def __draw_grid(self):
        """ Method to setup the grid itself"""
        width, height = self.canvas.winfo_width(), self.canvas.winfo_height()
        for i in range(0, self.grid.width):
            for j in range(0, self.grid.height):
                self.__draw_cell(i, j)


    def __canvas_clicked(self, event):
        """ Method for when the cell was clicked """
        x, y, width, height = event.x, event.y, self.canvas.winfo_width(), self.canvas.winfo_height()
        cell_x = int(x / width * self.grid.width)
        cell_y = int(y / height * self.grid.height)
        self.grid.switch_cell(cell_x, cell_y)
        self.__draw_cell(cell_x, cell_y)




if __name__ == "__main__":
    Ui(Tk(), cells.Grid(GRID_WIDTH, GRID_HEIGHT)).mainloop()

Answer 1

问题 1:

你的主要问题是，在 canvas 实际显示之前，canvas.winfo_width() 和 canvas.winfo_height() 没有 return canvas 的宽度和高度，但是值 1.

我建议您创建 canvas 如下：

# Define canvas and save dimensions
self.canvas_width = 300
self.canvas_height = 200
self.canvas = Canvas(self, width = self.canvas_width, 
                           height = self.canvas_height)

然后，在您的代码中，替换每个实例：

width, height = self.canvas.winfo_width(), self.canvas.winfo_height()

和

width, height = self.canvas_width, self.canvas_height

问题二：

创建每个单元格时，我认为您不需要在 x0 和 y0 上加 1。相反，它应该是：

x0 = width * x / self.grid.width
x1 = width * (x + 1) / self.grid.width
y0 = height * y / self.grid.height
y1 = height * (y + 1) / self.grid.height

Python Tkinter Canvas 没有出现

Python Tkinter Canvas does not appear

python

tkinter

tkinter-canvas