pyqtgraph：如何拖动一个绘图项

Question

我现在正在尝试在pyqtgraph中绘制一个散点图，并想要拖动图上的项目，但找不到合适的方法。
我已经查看了GraphicsScene的sigMouseClicked和sigMouseMoved事件。
欢迎任何建议。如果需要我提供更多细节，请告诉我。

我正在使用的示例代码：

import pyqtgraph as pg
import numpy as np

w = pg.GraphicsWindow()
w.show()
x = [2,4,5,6,8];
y = [2,4,6,8,10];

pl = pg.PlotItem()
pl.plot(x, y, symbol='o')
w.addItem(pl)

Answer 1

看看这个文件：pyqtgraph/examples/CustomGraphItem.py。这里的做法是创建一个叫做GraphItem的子类，这个子类可以捕捉鼠标拖动的事件，并且移动鼠标下方的散点图点。

def mouseDragEvent(self, ev):
    if ev.button() != QtCore.Qt.LeftButton:
        ev.ignore()
        return

    if ev.isStart():
        # We are already one step into the drag.
        # Find the point(s) at the mouse cursor when the button was first 
        # pressed:
        pos = ev.buttonDownPos()
        pts = self.scatter.pointsAt(pos)
        if len(pts) == 0:
            ev.ignore()
            return
        self.dragPoint = pts[0]
        ind = pts[0].data()[0]
        self.dragOffset = self.data['pos'][ind] - pos
    elif ev.isFinish():
        self.dragPoint = None
        return
    else:
        if self.dragPoint is None:
            ev.ignore()
            return

    ind = self.dragPoint.data()[0]
    self.data['pos'][ind] = ev.pos() + self.dragOffset
    self.updateGraph()
    ev.accept()