在 Python/tkinter/canvas 上：用户将单击一个项目，拖动到另一个项目并释放。项目本身不会被拖动/移动；我只需要这两个项目的标签。我观察到的问题是，当鼠标按下一个项目，然后拖动到另一个项目进行鼠标释放时，画布返回第一个项目 id#/标签作为事件 id#/标签。
鼠标坐标可以正确报告这两个事件，并且标签在其他方面都可以正常工作。
这是一个错误还是实施限制？有什么解决方法吗？还是我做错了？
下面的演示代码也位于 https://pastebin.com/MD9AuAUS
import tkinter as tk
from tkinter import ttk
from tkinter import messagebox
from functools import partial
'''
Ctag Tester v1.0
29 February 2020
Written for Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:06:47)
[MSC v.1914 32 bit (Intel)] on win32 / Windows 10 / VS Code (ide)
This is a demo of a tkinter / canvas bug. Or something. (?)
1. Each of the two squares on the canvas should report its tag
for a mouse-1-down and mouse-1-up event.
2. It always reports properly if you click and release on the same item.
3. PROBLEM: If you click down on one square and then drag to the other
square, the mouse-up event gives the same tag as the mouse-down event,
even though they did not occur on the same item.
4. The mouse x-y coordinates are also reported, and those always
report correctly wherever those two events occur.
5. What I assumed should happen is that the mouse-down event should get
the tag of the item that it occurs on, and the mouse-up event should get
the tag of the item that it occurs on.
'''
def main():
program = TestProgram1()
program.window.mainloop()
class TestProgram1:
def __init__(self):
self.window = tk.Tk()
self.window.title( "Ctag Tester v1.0" )
self.window_width = 800
self.window_height = 600
self.window.minsize(self.window_width, self.window_height)
self.window_position_x = 40
self.window_position_y = 40
self.window.geometry('%dx%d+%d+%d' % (self.window_width, self.window_height, self.window_position_x, self.window_position_y))
self.window.resizable(False, False)
x_pos = 20
y_pos = 20
self.staticlabel_38 = tk.Label(master=self.window, text="mousedown xy:")
self.staticlabel_38.place(x=x_pos, y=y_pos)
x_pos = 180
y_pos = 20
self.staticlabel_42 = tk.Label(master=self.window, text="mouseup xy:")
self.staticlabel_42.place(x=x_pos, y=y_pos)
x_pos = 20
y_pos = 50
self.label_mousedown = tk.Label(master=self.window, text="[none]")
self.label_mousedown.place(x=x_pos, y=y_pos)
x_pos = 180
y_pos = 50
self.label_mouseup = tk.Label(master=self.window, text="[none]")
self.label_mouseup.place(x=x_pos, y=y_pos)
x_pos = 20
y_pos = 100
self.staticlabel_55 = tk.Label(master=self.window, text="mousedown tag:")
self.staticlabel_55.place(x=x_pos, y=y_pos)
x_pos = 180
y_pos = 100
self.staticlabel_59 = tk.Label(master=self.window, text="mouseup tag:")
self.staticlabel_59.place(x=x_pos, y=y_pos)
x_pos = 20
y_pos = 130
self.label_tagdown = tk.Label(master=self.window, text="[none]")
self.label_tagdown.place(x=x_pos, y=y_pos)
x_pos = 180
y_pos = 130
self.label_tagup = tk.Label(master=self.window, text="[none]")
self.label_tagup.place(x=x_pos, y=y_pos)
x_pos = 350
y_pos = 40
self.canvas1 = tk.Canvas(master=self.window, width=400, height=400)
self.canvas1.place(x=x_pos, y=y_pos)
self.canvas1.create_rectangle(2, 2, 400, 400, outline='black', fill='white')
target_1 = self.canvas1.create_rectangle(80, 80, 180, 180, outline='black', fill='green', tags=('greenbox'))
self.canvas1.tag_bind('greenbox', '<Button-1>', partial(self.chart_item_mousedown_event, target_1))
self.canvas1.tag_bind('greenbox', '<ButtonRelease-1>', partial(self.chart_item_mouseup_event, target_1))
target_2 = self.canvas1.create_rectangle(240, 180, 340, 280, outline='black', fill='red', tags=('redbox'))
self.canvas1.tag_bind('redbox', '<Button-1>', partial(self.chart_item_mousedown_event, target_2))
self.canvas1.tag_bind('redbox', '<ButtonRelease-1>', partial(self.chart_item_mouseup_event, target_2))
def chart_item_mousedown_event(self, c_handle, event):
temp_tag = self.canvas1.gettags(c_handle)
if temp_tag == "":
self.label_tagdown.config(text='[none]')
else:
self.label_tagdown.config(text=temp_tag)
m_event = "x:" + str(event.x) + ", y:" + str(event.y)
self.label_mousedown.config(text=m_event)
def chart_item_mouseup_event(self, c_handle, event):
temp_tag = self.canvas1.gettags(c_handle)
if temp_tag == "":
self.label_tagup.config(text='[none]')
else:
self.label_tagup.config(text=temp_tag)
m_event = "x:" + str(event.x) + ", y:" + str(event.y)
self.label_mouseup.config(text=m_event)
if __name__ == "__main__":
main()
这不是一个错误，也不是一个真正的限制。这就是 tkinter 的设计原理。获取按钮按下事件的小部件和/或画布项目将接收后续释放事件。
您需要让绑定到释放事件的代码找到光标下方的画布项。
例如，给定一个事件对象，以下是如何找到最接近指针的画布项：
canvas = event.widget
canvasx = canvas.canvasx(event.x)
canvasy = canvas.canvasy(event.y)
item = canvas.find_closest(canvasx, canvasy)
正如 @Bryan Oakley 所说，您可以通过巧妙地利用拖动时 drag-end-event （鼠标释放）由 drag-start-component 接收这一事实，在 tkinter 中实现拖放行为，甚至如果当鼠标悬停在 drag-end-component 上时释放鼠标。
在拖结束事件中：
import tkinter as tk
def button_released(event: tk.Event):
drag_from = event.widget
drag_to = event.widget.winfo_containing(event.x_root, event.y_root)
if isinstance(drag_to, tk.Frame):
print(f"Dragged from Frame {frames.index(drag_from)} to Frame {frames.index(drag_to)}")
else:
print("Drag cancelled")
root = tk.Tk()
root.geometry("350x350")
frames = []
for i in range(2):
for j in range(2):
frame = tk.Frame(root, width=150, height=150, bg="lightblue")
frame.grid(row=i, column=j, padx=10, pady=10)
frame.bind("<ButtonRelease-1>", button_released)
frames.append(frame)
root.mainloop()