Question

如何在Canvas上的点上使用拖放技术？我没有在画布上找到任何插槽来连接鼠标点击。

class Canvas(QtGui.QWidget):
    def __init__(self, parent):
        super(Canvas, self).__init__(parent)
        self.setGeometry(0,0,200,200)

    def paintEvent(self, e):
        qp = QtGui.QPainter()
        qp.begin(self)
        self.drawPoints(qp)
        qp.end()

    def drawPoints(self, qp):
        qp.setPen(QtCore.Qt.red)
        size = self.size()

            #test
        x = 0
        y = 0
        for k in range(0,150,2):
            qp.drawPoint(x,y)
            x += 5
            y += 5

    #get the click coordinates
    def mousePressEvent(self, QMouseEvent):
        print QMouseEvent.pos()

Answer 1

拖拽技术或多或少是这样的：

点击：识别拖动对象
移动时：重绘拖动对象
发布时：更新最终状态

在第2步中，您还可以更新画布。这是该技术的一个例子。我使用numpy来管理积分（希望不要打扰你）。

from PyQt4 import QtGui,QtCore
import numpy as np

class Canvas(QtGui.QWidget):

    DELTA = 10 #for the minimum distance        

    def __init__(self, parent):
        super(Canvas, self).__init__(parent)
        self.draggin_idx = -1        
        self.setGeometry(0,0,200,200)
        self.points = np.array([[v*5,v*5] for v in range(75)], dtype=np.float)        

    def paintEvent(self, e):
        qp = QtGui.QPainter()
        qp.begin(self)
        self.drawPoints(qp)
        qp.end()

    def drawPoints(self, qp):
        qp.setPen(QtCore.Qt.red)
        for x,y in self.points:
            qp.drawPoint(x,y)        

    def _get_point(self, evt):
        return np.array([evt.pos().x(),evt.pos().y()])

    #get the click coordinates
    def mousePressEvent(self, evt):
        if evt.button() == QtCore.Qt.LeftButton and self.draggin_idx == -1:
            point = self._get_point(evt)
            #dist will hold the square distance from the click to the points
            dist = self.points - point
            dist = dist[:,0]**2 + dist[:,1]**2
            dist[dist>self.DELTA] = np.inf #obviate the distances above DELTA
            if dist.min() < np.inf:
                self.draggin_idx = dist.argmin()        

    def mouseMoveEvent(self, evt):
        if self.draggin_idx != -1:
            point = self._get_point(evt)
            self.points[self.draggin_idx] = point
            self.update()

    def mouseReleaseEvent(self, evt):
        if evt.button() == QtCore.Qt.LeftButton and self.draggin_idx != -1:
            point = self._get_point(evt)
            self.points[self.draggin_idx] = point
            self.draggin_idx = -1
            self.update()        

app = QtGui.QApplication([])

c = Canvas(None)
c.show()
app.exec_()

在画布上拖放一个点

1 个答案: