使用QPainterPath在两点之间绘制直线

Question

我有一个场景，我想用QPainterpath在两点之间画一条线（鼠标按下应该是起点，鼠标释放应该是终点）

这是我想要的一个演示

下面是我当前代码的情况

下面是我尝试过的代码

import sys
from PyQt5 import QtWidgets, QtCore, QtGui

class Scene(QtWidgets.QGraphicsScene):

    def __init__(self, *args, **kwargs):
        super(Scene, self).__init__(*args, **kwargs)
        self.point = QtCore.QPointF(0.0, 0.0)

        self.path = QtGui.QPainterPath()

        self.start_point = None
        self.end_point = None

        self.start = False

    def mousePressEvent(self, event):

        self.start_point = event.scenePos()
        self.start = True
        self.path = QtGui.QPainterPath(self.start_point)
        # self.addLine(self.line.setP1(self.start_point))

        super().mousePressEvent(event)

    def mouseMoveEvent(self, event):

        if self.start:
            self.path.lineTo(event.scenePos())
            # self.path.moveTo(event.scenePos())
            self.addPath(self.path, QtGui.QPen(QtCore.Qt.red))

        super(Scene, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):

        if self.start:
            print(self.path)
            self.path.lineTo(event.scenePos())
            # self.path.moveTo(event.scenePos())
            self.addPath(self.path, QtGui.QPen(QtCore.Qt.red))
            self.start = False

        super(Scene, self).mouseReleaseEvent(event)

def main():
    app = QtWidgets.QApplication(sys.argv)

    view = QtWidgets.QGraphicsView()
    view.setRenderHint(QtGui.QPainter.Antialiasing)

    view.setMouseTracking(True)
    scene = Scene()

    view.setScene(scene)
    view.show()
    
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

Answer 1

任何试图使用QLineF和QGraphicsLineItem实现此目的的人都可以使用Thx到@eyllansc 这是代码

import sys
from PyQt5 import QtWidgets, QtCore, QtGui


class Scene(QtWidgets.QGraphicsScene):
    def __init__(self, *args, **kwargs):
        super(Scene, self).__init__(*args, **kwargs)

        self.setSceneRect(QtCore.QRectF(0, 0, 500, 500))

        self.line = None
        self.graphics_line = None

        self.start_point = QtCore.QPointF()
        self.end_point = QtCore.QPointF()

    def mousePressEvent(self, event):
        self.start_point = event.scenePos()
        self.end_point = self.start_point

        self.line = QtCore.QLineF(self.start_point, self.end_point)
        self.graphics_line = QtWidgets.QGraphicsLineItem(self.line)

        self.update_path()
        super().mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if event.buttons() & QtCore.Qt.LeftButton:
            self.end_point = event.scenePos()
            self.update_path()
        super(Scene, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        self.end_point = event.scenePos()
        self.update_path()

        super(Scene, self).mouseReleaseEvent(event)

    def update_path(self):
        if not self.start_point.isNull() and not self.end_point.isNull():
            self.line.setP2(self.end_point)
            self.graphics_line.setLine(self.line)
            self.addItem(self.graphics_line)


def main():
    app = QtWidgets.QApplication(sys.argv)

    view = QtWidgets.QGraphicsView()
    view.setRenderHint(QtGui.QPainter.Antialiasing)

    view.setMouseTracking(True)
    scene = Scene()

    view.setScene(scene)
    view.show()

    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

Answer 2

每次使用lineTo时，都会创建一条新线，其中起点是最后添加的点，终点是传递给函数的点，因此可以看到曲线，因为它们是这些线的并集。解决方案是使用两个变量存储起点和终点，并在必要时进行更新，然后使用该信息更新QGraphicsPathItem，而不是QPainterPath。同样的概念也适用于QLineF的QGraphicsLineItem

class Scene(QtWidgets.QGraphicsScene):
    def __init__(self, *args, **kwargs):
        super(Scene, self).__init__(*args, **kwargs)

        self.path_item = self.addPath(QtGui.QPainterPath())

        self.start_point = QtCore.QPointF()
        self.end_point = QtCore.QPointF()

    def mousePressEvent(self, event):
        self.start_point = event.scenePos()
        self.end_point = self.start_point
        self.update_path()
        super().mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if event.buttons() & QtCore.Qt.LeftButton:
            self.end_point = event.scenePos()
            self.update_path()
        super(Scene, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        self.end_point = event.scenePos()
        self.update_path()
        super(Scene, self).mouseReleaseEvent(event)

    def update_path(self):
        if not self.start_point.isNull() and not self.end_point.isNull():
            path = QtGui.QPainterPath()
            path.moveTo(self.start_point)
            path.lineTo(self.end_point)
            self.path_item.setPath(path)