如何在 tkinter 中的 canvas 项上实现鼠标悬停回调？

Question

我使用在互联网上找到的以下代码在 python 中实现了鼠标悬停操作：

from tkinter import *
import numpy as np

class rect:
    def __init__(self, root):
        self.root = root
        self.size = IntVar()
        self.canvas = Canvas(self.root, width=800, height=300)
        self.scale = Scale(self.root, orient=HORIZONTAL, from_=3, to=20, tickinterval=1, variable=self.size)
        self.scale.bind('<ButtonRelease>', self.show)
        self.canvas.bind('<Motion>', self.motion)
        self.board = []
        self.array = np.zeros((self.scale.get(),self.scale.get())).tolist()
        self.canvas.pack()
        self.scale.pack()

    def motion(self,event):
        if self.canvas.find_withtag(CURRENT):
            current_color = self.canvas.itemcget(CURRENT, 'fill')
            self.canvas.itemconfig(CURRENT, fill="cyan")
            self.canvas.update_idletasks()
            self.canvas.after(150)
            self.canvas.itemconfig(CURRENT, fill=current_color)

    def show(self,event):
        self.canvas.delete('all')
        x = 50
        y = 50
        row = []
        self.board.clear()
        for i in range(self.scale.get()):
            row = []
            for j in range(self.scale.get()):
                rectangle = self.canvas.create_rectangle(x, y, x + 50, y + 50, fill='red')
                x += 50
                row.append(rectangle)
            x -= j*50
            y +=50
            self.board.append(row)
        print(self.board)

root = Tk()
a = rect(root)
root.mainloop()

执行的问题是项目的颜色仅在有限的时间内变为蓝色。

我需要 canvas 中每个项目的颜色在我进入其区域时更改并保持蓝色直到鼠标离开该项目。

Answer 1

我更改了 motion 方法并将 self.last = None 添加到 __init__ 方法：

from tkinter import *
import numpy as np

class rect:
    def __init__(self, root):
        self.root = root
        self.size = IntVar()
        self.canvas = Canvas(self.root, width=800, height=300)
        self.scale = Scale(self.root, orient=HORIZONTAL, from_=3, to=20, tickinterval=1, variable=self.size)
        self.scale.bind('<ButtonRelease>', self.show)
        self.canvas.bind('<Motion>', self.motion)
        self.board = []
        self.array = np.zeros((self.scale.get(),self.scale.get())).tolist()
        self.canvas.pack()
        self.scale.pack()
        self.last = None

    def motion(self, event):
        temp = self.canvas.find_withtag(CURRENT)
        if temp == self.last:
            self.canvas.itemconfig(CURRENT, fill="cyan")
            self.canvas.update_idletasks()
        else:
            self.canvas.itemconfig(self.last, fill="red")
        self.last = temp

    def show(self,event):
        self.canvas.delete('all')
        x = 50
        y = 50
        row = []
        self.board.clear()
        for i in range(self.scale.get()):
            row = []
            for j in range(self.scale.get()):
                rectangle = self.canvas.create_rectangle(x, y, x + 50, y + 50, fill='red')
                x += 50
                row.append(rectangle)
            x -= j*50
            y +=50
            self.board.append(row)
        print(self.board)

root = Tk()
a = rect(root)
root.mainloop()

Answer 2

您可以在创建矩形时传递参数 activefill。

来自effboot.org：

Fill color to use when the mouse pointer is moved over the item, if different from fill.

为此，替换：

rectangle = self.canvas.create_rectangle(x, y, x + 50, y + 50, fill='red')

作者：

rectangle = self.canvas.create_rectangle(x, y, x + 50, y + 50, fill='red', activefill='cyan')

这消除了将 Motion 绑定到您的 canvas 的需要，并且还使代码明显更短：

from tkinter import *
import numpy as np

class rect:
    def __init__(self, root):
        self.root = root
        self.size = IntVar()
        self.canvas = Canvas(self.root, width=800, height=300)
        self.scale = Scale(self.root, orient=HORIZONTAL, from_=3, to=20, tickinterval=1, variable=self.size)
        self.scale.bind('<ButtonRelease>', self.show)
        self.board = []
        self.array = np.zeros((self.scale.get(),self.scale.get())).tolist()
        self.canvas.pack()
        self.scale.pack()

    def show(self,event):
        self.canvas.delete('all')
        x = 50
        y = 50
        row = []
        self.board.clear()
        for i in range(self.scale.get()):
            row = []
            for j in range(self.scale.get()):
                rectangle = self.canvas.create_rectangle(x, y, x + 50, y + 50, fill='red', activefill='cyan')
                x += 50
                row.append(rectangle)
            x -= j*50
            y +=50
            self.board.append(row)
        print(self.board)

root = Tk()
a = rect(root)
root.mainloop()

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