Question

下面是通过单击拖动和释放绘制矩形的代码...由于某些原因它不起作用，画布屏幕显示但矩形不被绘制？它是root.mainloop（）行吗？因为我改变它是因为我需要绘制弧线和线条而且不能只有app = rectangle和app.mainloop ...对不起，我真的很陌生。

from tkinter import Canvas, Tk, mainloop
import tkinter as tk 
from PIL import Image, ImageTk

# Image dimensions
w,h = 800,400

# Create canvas
root = Tk()
canvas = Canvas(root, width = w, height = h, bg='#D2B48C', cursor = "cross")
canvas.pack()


class Rectangle(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.x = self.y = 0
        self.canvas.pack(side="top", fill = "both", expand = True)
        self.canvas.bind("<ButtonPress-1>", self.press)
        self.canvas.bind("<B1-Motion>", self.move)
        self.canvas.bind("<ButtonRelease-1>", self.release)
        self.rect = None
        self.start_x = None
        self.start_y = None

    def press(self, event):
        # save mouse drag start position
        self.start_x = event.x
        self.start_y = event.y
        self.rect = self.canvas.create_rectangle(self.x, self.y, 1, 1, fill="red")

    def move(self, event):
        mouseX, mouseY = (event.x, event.y)

        # expand rectangle as you drag the mouse
        self.canvas.coords(self.rect, self.start_x, self.start_y, mouseX, mouseY)

    def release(self, event):
        pass

# Other Classes for arc and pencil begin here

root.mainloop()

谢谢大家!!!

Answer 1

作为 @BryanOakley 评论，提供的来源包含未完成的分析，并揭示了对tkinter使用的误解。

问题1 - class Rectangle不需要继承tk.Tk。

不是从class Rectangle继承tk.Tk，而是添加。{ 实例创建时Canvas实例。

 class Rectangle(): # not inherit from ==> tk.Tk):
    def __init__(self,canvas):
        # not initialize a second Tk instance ==> tk.Tk.__init__(self)
        self.x = self.y = 0
        #  attach the main canvas
        self.canvas = canvas
        self.canvas.pack(side="top", fill = "both", expand = True)

而不是：

class Rectangle(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.x = self.y = 0
        self.canvas.pack(side="top", fill = "both", expand = True)

问题2 - 尚未创建class Rectangle的实例。

要使用class Rectangle，应创建一个实例   附加到canvas实例!!

之前，在Tk()和Canvas()之前移动课程声明   创建

class Rectangle(tk.Tk):
    def __init__(self):
...
    def release(self, event):
        pass

# Other Classes for arc and pencil begin here

root = Tk()
canvas = Canvas(root, width = w, height = h, bg='#D2B48C', cursor = "cross")
canvas.pack()

# create the Rectangle instance
hRect = Rectangle(canvas)

root.mainloop()

而不是：

root = Tk()
canvas = Canvas(root, width = w, height = h, bg='#D2B48C', cursor = "cross")
canvas.pack()

class Rectangle(tk.Tk):
    def __init__(self):
...
    def release(self, event):
        pass

# Other Classes for arc and pencil begin here

root.mainloop()

Answer 2

首先，你永远不会创建Rectangle类的实例，这是你所有逻辑的所在。

另一方面，您只能拥有Tk的单个实例。您可以在问题开始时创建一个，然后在创建Rectangle实例时再创建另一个。同样，你只能有一个。

绘制矩形tkinter不起作用

2 个答案: