import numpy as np
import matplotlib.pyplot as plt

def onMotion(event):
    # 获取鼠标位置和标注可见性
    x = event.xdata
    y = event.ydata
    visible = annot.get_visible()
    if event.inaxes == ax:
        # 测试鼠标事件是否发生在曲线上
        contain, _ = sinCurve.contains(event)
        if contain:
            # 设置标注的终点和文本位置，设置标注可见
            annot.xy = (x, y)
            annot.set_text(str(y))   # 设置标注文本
            annot.set_visible(True)  # 设置标注可见
        else:
            # 鼠标不在曲线附近，设置标注为不可见
            if visible:
                annot.set_visible(False)
        event.canvas.draw_idle()
        
def onEnter(event):
    # 鼠标进入时修改轴的颜色
    event.inaxes.patch.set_facecolor('yellow')
    event.canvas.draw_idle()

def onLeave(event):
    # 鼠标离开时恢复轴的颜色
    event.inaxes.patch.set_facecolor('white')
    event.canvas.draw_idle()
    
fig = plt.figure()
ax = fig.gca()
x = np.arange(0, 2*np.pi, 0.01)
y = np.sin(x)
sinCurve, = plt.plot(x, y,      # 绘图数据
                     picker=2)  # 鼠标距离曲线2个像素可识别
# sinCurve.set_pickradius(2)
# 创建标注对象
annot = ax.annotate("",
                    xy=(0,0),                    # 箭头位置
                    xytext=(-50,50),             # 文本相对位置
                    # 相对于xy的偏移量单位
                    textcoords="offset pixels",
                    # 圆角，红色背景
                    bbox=dict(boxstyle="round", fc="r"),
                    # 标注箭头形状
                    arrowprops=dict(arrowstyle="->"))
annot.set_visible(False)

# 添加事件处理函数
fig.canvas.mpl_connect('motion_notify_event', onMotion)  
fig.canvas.mpl_connect('axes_enter_event', onEnter)
fig.canvas.mpl_connect('axes_leave_event', onLeave)

plt.show()