如何在 tkinter Canvas 中检测点击对象的标签？

Posted 2023-02-23

【中文标题】如何在 tkinter Canvas 中检测点击对象的标签？

【英文标题】：How do I detect tags of clicked objects in tkinter Canvas?

【发布时间】：2022-01-22 04:40:00

【问题描述】：

我想问一下如何检测Python中的标签tkinter.Canvas()。我已经设置了一个带有一些基本画布对象的示例程序，并且所有这些对象都已分配给某个标签。如果我单击对象但不知道该怎么做，我想要的是获取该标记值。例如，当我有此代码时：

import tkinter
canvas = tkinter.Canvas(width=800, height=400)
canvas.pack()

canvas.create_line(20, 100, 150, 350, tags="lines")
canvas.create_line(50, 20, 300, 20, tags="lines")
canvas.create_oval(200, 250, 300, 350, fill="yellow", tags="ovals")
canvas.create_oval(400, 250, 500, 350, fill="blue", tags="ovals")

for j in range(4):
    for i in range(10):
        canvas.create_rectangle(i * 70 + 10, j * 60 + 10, i * 70 + 60, j * 60 + 50, fill="lightblue", tags=f"square_j_i")

def click(coords):
    print(coords.x, coords.y)

canvas.bind("<Button-1>", click)

我想获得这些值，例如lines、ovals、square_5_4、square_7_1 等。有人知道该怎么做吗？ O:)

【参考方案1】：

您无需遍历所有项目即可获取画布项目的标签。画布上被点击的任何项目都分配有"current" 标签。

您只需使用canvas.find_withtag 和canvas.gettags 或将"current" 直接传递给gettags，它将返回与画布项关联的所有标签。

import tkinter


canvas = tkinter.Canvas(width=800, height=400)
canvas.pack()

canvas.create_line(20, 100, 150, 350, tags="lines")
canvas.create_oval(400, 250, 500, 350, fill="blue", tags="ovals")

for j in range(4):
    for i in range(10):
        canvas.create_rectangle(i * 70 + 10, j * 60 + 10, i * 70 + 60, j * 60 + 50, fill="lightblue", tags=f"square_j_i")

def click(event):

    #currently_clicked = canvas.find_withtag("current")
    #if currently_clicked:
    print(canvas.gettags("current")) # the first index will contain your desired output
   
canvas.bind("<Button-1>", click)
canvas.mainloop()

【参考方案2】：

作为评论中的@Matiiss suggest，您可以使用Canvas 对象的tag_bind() 方法将回调函数绑定到特定事件，例如按钮1 单击它们。下面的代码（基于您的代码）说明了这样的事情是如何完成的。

它创建匿名的lambda 函数，调用通用的pick() 点击事件处理函数，并将原始事件对象加上当前与对象。

import tkinter

def pick(event, tag):
    print(f'tag: tag!r, coords: event.x, event.y')

canvas = tkinter.Canvas(width=800, height=400)
canvas.pack()

canvas.create_line(20, 100, 150, 350, tags='lines')
canvas.create_line(50, 20, 300, 20, tags='lines')
canvas.tag_bind('lines', '<Button-1>', lambda event: pick(event, 'lines'))

canvas.create_oval(200, 250, 300, 350, fill='yellow', tags='ovals')
canvas.create_oval(400, 250, 500, 350, fill='blue', tags='ovals')
canvas.tag_bind('ovals', '<Button-1>', lambda event: pick(event, 'ovals'))

for j in range(4):
    for i in range(10):
        tag = f'square_j_i'
        canvas.create_rectangle(i*70 + 10, j*60 + 10, i*70 + 60, j*60 + 50,
                                fill='lightblue', tags=tag)
        canvas.tag_bind(tag, '<Button-1>', lambda event, tag=tag: pick(event, tag))

tkinter.mainloop()

【参考方案3】：

您可以遍历画布上的所有项目 ID，获取它们的标签并绑定一个函数以单击该对象（如果您需要画布上的所有对象（在 for 循环之前创建）以这样做）：

import tkinter as tk


root = tk.Tk()

canvas = tk.Canvas(root, width=800, height=400)
canvas.pack()

canvas.create_line(20, 100, 150, 350, tags="lines")
canvas.create_line(50, 20, 300, 20, tags="lines")
canvas.create_oval(200, 250, 300, 350, fill="yellow", tags="ovals")
canvas.create_oval(400, 250, 500, 350, fill="blue", tags="ovals")

for j in range(4):
    for i in range(10):
        canvas.create_rectangle(i * 70 + 10, j * 60 + 10, i * 70 + 60, j * 60 + 50, fill="lightblue", tags=f"square_j_i")


# loop over all items on the canvas, get their first tag (for simplicity) and bind that tag
# to clicking on the object and make that call the function that will print the tag name
# use a default value so that the correct tag is printed
for item_id in canvas.find_all():
    tag = canvas.gettags(item_id)[0]
    canvas.tag_bind(tag, '<Button-1>', lambda _, t=tag: print(t))

root.mainloop()