Matplotlib 中的事件处理

基于事件的系统通常是一组重复出现的模式的一部分。通常，它们包括以下内容：

• 传入事件
• 用于响应事件的机制
• 循环结构（例如，while 循环、监听器和消息分发机制）

触发的事件也更丰富一些，包括事件发生在哪个 Axes 等信息。这些事件还了解 Matplotlib 坐标系，并以像素坐标和数据坐标报告事件位置。

句法：

figure.canvas.mpl_connect( Event_name , callback function or method)

参数：

• Event_name：它可以是下表中的任何一个
• callback_function：它将定义处理事件。

事件列表

Event_name	class	Description
button_press_event	MouseEvent	The mouse button is pressed
button_release_event	MouseEvent	The mouse button is released
draw_event	DrawEvent	The canvas draw occurs
key_press_event	KeyEvent	A key is pressed
key_release_event	KeyEvent	A key is released
motion_notify_event	MouseEvent	The motion of the mouse
pick_event	PickEvent	An object in the canvas is selected
resize_event	ResizeEvent	The figure canvas is resized
scroll_event	MouseEvent	The scroll wheel of the mouse is rolled
figure_enter_event	LocationEvent	The mouse enters a figure
axes_enter_event	LocationEvent	The mouse enters an axes object
axes_leave_event	LocationEvent	The mouse leaves an axes object
figure_leave_event	LocationEvent	The mouse leaves a figure

注意：这些类是在 matplotlib.backend_bases 中定义的

鼠标事件

• button_press_event：此事件涉及鼠标按钮按下
• button_release_event：此事件涉及鼠标按钮释放
• scroll_event：此事件涉及鼠标的滚动
• motion_notify_event：此事件涉及与鼠标移动有关的通知

例子：

我们使用了 mpl_connect 方法，如果您想在绘图中提供自定义用户交互功能，则必须调用该方法。此方法将采用两个参数：

• 事件的字符串值，可以是上表事件名称列中列出的任意值
• 回调函数或方法

Python3

# importing the necessary modules
from IPython.display import Image
import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
import time
import sys
import random
import matplotlib
matplotlib.use('nbagg')
  
  
class MouseEvent:
    
    # initialization
    def __init__(self):
        (figure, axes) = plt.subplots()
        axes.set_aspect(1)
        figure.canvas.mpl_connect('button_press_event', self.press)
        figure.canvas.mpl_connect('button_release_event', self.release)
  
    # start event to show the plot
    def start(self):
        plt.show()  # display the plot
  
    # press event will keep the starting time when u 
    # press mouse button
    def press(self, event):
        self.start_time = time.time()
  
    # release event will keep the track when you release
    # mouse button
    def release(self, event):
        self.end_time = time.time()
        self.draw_click(event)
  
    # drawing the plot
    def draw_click(self, event):
        # size = square (4 * duration of the time button 
        # is keep pressed )
        size = 4 * (self.end_time - self.start_time) ** 2
          
        # create a point of size=0.002 where mouse button 
        # clicked on the plot
        c1 = plt.Circle([event.xdata, event.ydata], 0.002,)
          
        # create a circle of radius 0.02*size
        c2 = plt.Circle([event.xdata, event.ydata], 0.02 * size, alpha=0.2)
        event.canvas.figure.gca().add_artist(c1)
        event.canvas.figure.gca().add_artist(c2)
        event.canvas.figure.show()
  
  
cbs = MouseEvent()
  
# start the event
cbs.start()

输出 ：

示例 2：

我们将使用 draw_click 方法添加颜色

Python3

def draw_click(self, event):
    
    # you can specified your own color list
    col = ['magneta', 'lavender', 'salmon', 'yellow', 'orange']
    cn = random.randint(0, 5)
      
    # size = square (4 * duration of the time button 
    # is keep pressed )
    size = 4 * (self.end_time - self.start_time) ** 2
      
    # create a point of size=0.002 where mouse button 
    # clicked on the plot
    c1 = plt.Circle([event.xdata, event.ydata], 0.002,)
      
    # create a circle of radius 0.02*size
    c2 = plt.Circle([event.xdata, event.ydata], 0.02 *
                    size, alpha=0.2, color=col[cn])
    event.canvas.figure.gca().add_artist(c1)
    event.canvas.figure.gca().add_artist(c2)
    event.canvas.figure.show()

输出：