[英]How to get the direction of <Motion> in tkinter?
我正在嘗試獲取 tkinter <Motion>
(實際上是<B1-Motion>
)事件的方向。
我已經嘗試使用event.direction
(error), event.keysym
(??) 和 event 本身給了我一些坐標。
所以這是我到目前為止的代碼:
def holdanddrag(event):
print('Direction: '+event. … ) # here I need some help
Widget.bind('<B1-Motion>', holdanddrag)
有誰知道該怎么做? 提前致謝!
為了確定方向,您必須存儲previous position
,並使用它來計算到actual position
的運動方向(歸一化向量)。 這些變量必須在運動發生時更新。
下面是一個小例子,在畫布上繪制一個與鼠標拖動方向對應的向量(箭頭):
import math
import tkinter as tk
from collections import deque
class Vector:
"""small class for vector arithmetic convenience
"""
def __init__(self, x: float=0, y: float=0) -> None:
self.x = x
self.y = y
def __str__(self) -> str:
return f'({self.x}, {self.y})'
def __mul__(self, scalar: float) -> 'Vector':
return Vector(self.x * scalar, self.y * scalar)
def magnitude(self) -> float:
return math.hypot(self.x, self.y)
def normalize(self) -> 'Vector':
mag = self.magnitude()
return Vector(self.x / mag, self.y / mag) if mag != 0 else Vector()
def __repr__(self) -> str:
return str(self)
def __iter__(self) -> float:
yield self.x
yield self.y
class Point:
"""small class for point arithmetic convenience
"""
def __init__(self, x: float, y: float):
self.x = x
self.y = y
def __sub__(self, other: 'Point') -> Vector:
return Vector(other.x - self.x, other.y - self.y)
def __add__(self, vec: Vector) -> 'Point':
return Point(self.x + vec.x, self.y + vec.y)
def __str__(self) -> str:
return f'({self.x}, {self.y})'
def __repr__(self) -> str:
return str(self)
def __iter__(self) -> float:
yield self.x
yield self.y
def draw_dir(canvas, start_point: Point, _vid=[None]) -> None:
"""draws and updates the scaled normalized direction vector
on the canvas.
Keeps track of the id of the canvas item last drawn
"""
if _vid[0] is not None:
canvas.delete(_vid[0])
normed_scaled_v = direct.normalize() * -50
end_point = start_point + normed_scaled_v
_vid[0] = canvas.create_line(*start_point, *end_point, arrow=tk.LAST)
_maxlen = 4
def direction(event, _direct=deque([Vector(0, 0) for _ in range(_maxlen)], maxlen=_maxlen)) -> None:
"""stores previous position, and uses it to calculate the direction
from the current position.
updates these variables
"""
global direct
_direct.append(Point(event.x, event.y))
p0, p1 = _direct[0], _direct[-1]
direct = p1 - p0
draw_dir(canvas, p1)
# print(_direct, direct)
direct = Vector(0, 0)
root = tk.Tk()
canvas = tk.Canvas(root, bg='cyan')
canvas.pack()
canvas.bind('<B1-Motion>', direction)
root.mainloop()
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