简单的Tk应用程序-点击按钮即可绘制

Question

有人能告诉我为什么当单击self.rec按钮时，我的"addLine"方法无法调用吗？

from tkinter import *
from tkinter import ttk
root = Tk()
class Paint:
    def __init__(self, parent):
        self.parent = parent
        self.whiteBoard = Canvas(self.parent)
        self.whiteBoard.grid(column=0, row=0, sticky=(N,W,E,S))
        self.lastx = 0
        self.lasty = 0
        self.rec = self.whiteBoard.create_rectangle((10, 10, 30, 30), fill="red")
        self.whiteBoard.tag_bind(self.rec, "<Button-1>", self.getClick)
    def xy(self, event):
        self.lastx, self.lasty = event.x, event.y
        print (event.x, " is the x coordinate")
        print (event.y, " is the y coordinate")
    def addLine(self, event):
        canvas.create_line((lastx, lasty, event.x, event.y))
        self.lastx, self.lasty = event.x, event.y
    def getClick(self, event):
        self.whiteBoard.bind("<Button-1>", self.xy)
        self.whiteBoard.bind("B1-Motion>", self.addLine)
white = Paint(root)
root.mainloop()

这都是尝试使用Tkinter制作MS绘画克隆的一部分。

Answer 1

首先，绑定到B1-Motion>（注意缺少<）。但是，更重要的是，不要进行这样的绑定。看起来getClick方法实际上是"选择线工具"。然后，将绑定<Button-1>和<B1-Motion>添加到画布本身。调用回调时，将根据所选工具执行操作。

以下是遵循此建议的粗略草图（附带RECTANGLE工具）：

import tkinter
# TOOLS
LINE, RECTANGLE = list(range(2))
class Paint:
    def __init__(self, canvas):
        self.canvas = canvas
        self._tool, self._obj = None, None
        self.lastx, self.lasty = None, None
        self.canvas.bind('<Button-1>', self.update_xy)
        self.canvas.bind('<B1-Motion>', self.draw)
    def draw(self, event):
        if self._tool is None or self._obj is None:
            return
        x, y = self.lastx, self.lasty
        if self._tool in (LINE, RECTANGLE):
            self.canvas.coords(self._obj, (x, y, event.x, event.y))
    def update_xy(self, event):
        if self._tool is None:
            return
        x, y = event.x, event.y
        if self._tool == LINE:
            self._obj = self.canvas.create_line((x, y, x, y))
        elif self._tool == RECTANGLE:
            self._obj = self.canvas.create_rectangle((x, y, x, y))
        self.lastx, self.lasty = x, y
    def select_tool(self, tool):
        print('Tool', tool)
        self._tool = tool
class Tool:
    def __init__(self, whiteboard, parent=None):
        self.whiteboard = whiteboard
        frame = tkinter.Frame(parent)
        self._curr_tool = None
        for i, (text, t) in enumerate((('L', LINE), ('R', RECTANGLE))):
            lbl = tkinter.Label(frame, text=text, width=2, relief='raised')
            lbl._tool = t
            lbl.bind('<Button-1>', self.update_tool)
            lbl.pack(padx=6, pady=6*(i % 2))
        frame.pack(side='left', fill='y', expand=True, pady=6)
    def update_tool(self, event):
        lbl = event.widget
        if self._curr_tool:
            self._curr_tool['relief'] = 'raised'
        lbl['relief'] = 'sunken'
        self._curr_tool = lbl
        self.whiteboard.select_tool(lbl._tool)

root = tkinter.Tk()
canvas = tkinter.Canvas(highlightbackground='black')
whiteboard = Paint(canvas)
tool = Tool(whiteboard)
canvas.pack(fill='both', expand=True, padx=6, pady=6)
root.mainloop()