如何在Python中使用按钮在画布上移动项目？

Question

我正在尝试修改此处发布的示例脚本：

board-drawing code to move an oval

原始脚本允许您单击并拖动画布周围的对象。我改变它，以便按钮移动第一个对象，但我得到一个按钮错误： TypeError：button_move（）只需2个参数（给定1个） 我不明白第二个论点应该是什么。

以下是修改过的脚本：

import Tkinter as tk

class Example(tk.Frame):
    '''Illustrate how to drag items on a Tkinter canvas'''

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

        # create a canvas
        self.canvas = tk.Canvas(width=400, height=400)
        self.canvas.pack(fill="both", expand=True)

        # this data is used to keep track of an 
        # item being dragged
        self._drag_data = {"x": 0, "y": 0, "item": None}

        # create a couple of movable objects
        self._create_token((100, 100), "white")
        self._create_token((200, 100), "black")

        # add bindings for clicking, dragging and releasing over
        # any object with the "token" tag
        self.canvas.tag_bind("token", "<ButtonPress-1>", self.on_token_press)
        self.canvas.tag_bind("token", "<ButtonRelease-1>", self.on_token_release)
        self.canvas.tag_bind("token", "<B1-Motion>", self.on_token_motion)
#-----------------------------------------------------------------------------
        self.canvas.button2 = tk.Button(self.canvas, text="Button Test",
                                 command=self.button_move)
        self.canvas.button2.config(bg="cyan",fg="black")
        self.canvas.button2.pack(side='top')

        self.canvas.tag_bind("button2", "<ButtonPress-1>", self.button_move)
#-----------------------------------------------------------------------------
    def _create_token(self, coord, color):
        '''Create a token at the given coordinate in the given color'''
        (x,y) = coord
        self.canvas.create_oval(x-25, y-25, x+25, y+25, 
                                outline=color, fill=color, tags="token")

    def on_token_press(self, event):
        '''Begining drag of an object'''
        # record the item and its location
        self._drag_data["item"] = self.canvas.find_closest(event.x, event.y)[0]
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def on_token_release(self, event):
        '''End drag of an object'''
        # reset the drag information
        self._drag_data["item"] = None
        self._drag_data["x"] = 0
        self._drag_data["y"] = 0

    def on_token_motion(self, event):
        '''Handle dragging of an object'''
        # compute how much the mouse has moved
        delta_x = event.x - self._drag_data["x"]
        delta_y = event.y - self._drag_data["y"]
        # move the object the appropriate amount
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        # record the new position
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y
#-----------------------------------------------------------------------------
    def button_move(self, event):
        '''Handle dragging of an object'''
        # set movement amount
        delta_x = 15
        delta_y = 15
        # move the object the appropriate amount
        #self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        self.canvas.move(self._drag_data[1], delta_x, delta_y)
        # record the new position
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y
#-----------------------------------------------------------------------------
if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

Answer 1

command=执行没有event的函数，但您指定的函数需要event - command=self.button_move - ＆gt; def button_move(self, event)

但bind与event执行相同的功能，因此您需要使用此event函数。

解决方案：使用事件的默认值，即None

def button_move(self, event=None):

但如果您使用event.x

执行什么，则无法在此函数中使用event.y，command=

Answer 2

以下是使用furas建议的更新代码：

import Tkinter as tk

class Example(tk.Frame):
    '''Illustrate how to drag items on a Tkinter canvas'''

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

        # create a canvas
        self.canvas = tk.Canvas(width=400, height=400)
        self.canvas.pack(fill="both", expand=True)

        # this data is used to keep track of an 
        # item being dragged
        self._drag_data = {"x": 0, "y": 0, "item": None}

        # create a couple of movable objects
        self._create_token((100, 100), "white")
        self._create_token((200, 100), "black")

        # add bindings for clicking, dragging and releasing over
        # any object with the "token" tag
        self.canvas.tag_bind("token", "<ButtonPress-1>", self.on_token_press)
        self.canvas.tag_bind("token", "<ButtonRelease-1>", self.on_token_release)
        self.canvas.tag_bind("token", "<B1-Motion>", self.on_token_motion)
#-----------------------------------------------------------------------------
        self.canvas.button2 = tk.Button(self.canvas, text="Button Test",
                                 command=self.button_move)
        self.canvas.button2.config(bg="cyan",fg="black")
        self.canvas.button2.pack(side='top')

        self.canvas.tag_bind("button2", "<ButtonPress-1>", self.button_move)
#-----------------------------------------------------------------------------
    def _create_token(self, coord, color):
        '''Create a token at the given coordinate in the given color'''
        (x,y) = coord
        self.canvas.create_oval(x-25, y-25, x+25, y+25, 
                                outline=color, fill=color, tags="token")

    def on_token_press(self, event):
        '''Begining drag of an object'''
        # record the item and its location
        self._drag_data["item"] = self.canvas.find_closest(event.x, event.y)[0]
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def on_token_release(self, event):
        '''End drag of an object'''
        # reset the drag information
        self._drag_data["item"] = None
        self._drag_data["x"] = 0
        self._drag_data["y"] = 0

    def on_token_motion(self, event):
        '''Handle dragging of an object'''
        # compute how much the mouse has moved
        delta_x = event.x - self._drag_data["x"]
        delta_y = event.y - self._drag_data["y"]
        # move the object the appropriate amount
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        # record the new position
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y
#-----------------------------------------------------------------------------
    def button_move(self, event=None):
        '''Handle dragging of an object'''
        # set movement amount
        delta_x = 15
        delta_y = 15
        # move the object the appropriate amount
        #self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        #self.canvas.move(self._drag_data[1], delta_x, delta_y)
        self.canvas.move(1, delta_x, delta_y) # moves item 1, when cursor is over token
        # record the new position
        #self._drag_data["x"] = event.x
        #self._drag_data["y"] = event.y
#-----------------------------------------------------------------------------
if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

Answer 3

当您将button_move()之类的回调配置为按钮的command时，调用它时唯一的参数是self，就像您这样调用它一样：< / p>

self.button_move()

但由于button_move()还需要event参数，因此会出现以下错误：

TypeError: button_move() takes exactly 2 arguments (1 given).

因此，从event定义中移除button_move()参数将是第一步。

此外，由于event不在button_move()范围内，您应该删除这两行：

self._drag_data["x"] = event.x
self._drag_data["y"] = event.y

最后，您需要要移动的画布对象的id才能使self.canvas.move()行生效。我建议你删除这行

self._drag_data["item"] = None

来自on_token_release()的

，以便上次点击的画布对象中的id保存在self._drag_data["item"]中。然后，您需要做的就是在尝试拨打self._drag_data["item"]之前检查canvas.move()是否不是。

应用所有这些更改会产生以下代码：

import Tkinter as tk

class Example(tk.Frame):
    '''Illustrate how to drag items on a Tkinter canvas'''

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

        # create a canvas
        self.canvas = tk.Canvas(width=400, height=400)
        self.canvas.pack(fill="both", expand=True)

        # this data is used to keep track of an
        # item being dragged
        self._drag_data = {"x": 0, "y": 0, "item": None}

        # create a couple of movable objects
        self._create_token((100, 100), "white")
        self._create_token((200, 100), "black")

        # add bindings for clicking, dragging and releasing over
        # any object with the "token" tag
        self.canvas.tag_bind("token", "<ButtonPress-1>", self.on_token_press)
        self.canvas.tag_bind("token", "<ButtonRelease-1>", self.on_token_release)
        self.canvas.tag_bind("token", "<B1-Motion>", self.on_token_motion)

        self.canvas.button2 = tk.Button(self.canvas, text="Button Test",
                                 command=self.button_move)
        self.canvas.button2.config(bg="cyan",fg="black")
        self.canvas.button2.pack(side='top')

        self.canvas.tag_bind("button2", "<ButtonPress-1>", self.button_move)

    def _create_token(self, coord, color):
        '''Create a token at the given coordinate in the given color'''
        (x,y) = coord
        self.canvas.create_oval(x-25, y-25, x+25, y+25,
                                outline=color, fill=color, tags="token")

    def on_token_press(self, event):
        '''Begining drag of an object'''
        # record the item and its location
        self._drag_data["item"] = self.canvas.find_closest(event.x, event.y)[0]
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def on_token_release(self, event):
        '''End drag of an object'''
        # reset the drag information
        self._drag_data["x"] = 0
        self._drag_data["y"] = 0

    def on_token_motion(self, event):
        '''Handle dragging of an object'''
        # compute how much the mouse has moved
        delta_x = event.x - self._drag_data["x"]
        delta_y = event.y - self._drag_data["y"]
        # move the object the appropriate amount
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        # record the new position
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def button_move(self):
        if not self._drag_data["item"]:
            return

        '''Handle dragging of an object'''
        # set movement amount
        delta_x = 15
        delta_y = 15
        # move the object the appropriate amount
        #self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)

if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()