PyQt5之QGraphics 003 GraphicsItem的移动

这一次，简介一下GraphicsItem的移动。代码如下：

"""
QGraphicsItem 的基本缩放
By Linyoubiao
2020-03-17
"""
from PyQt5.QtWidgets import (QApplication, QGraphicsView, QGraphicsScene,
                             QGraphicsItem)
from PyQt5.QtCore import (QPoint, QPointF, QLine, QLineF, QRect, QRectF,
                          QTime, qrand, Qt)
from PyQt5.QtGui import (QBrush, QPen, QColor, QRadialGradient,
                         QPainter, QPainterPath,
                         QPixmap, QImage, QPicture)
import math


class Node(QGraphicsItem):

    def __init__(self, graphWidget):
        super(Node, self).__init__()

        self.graph = graphWidget

        self.setFlag(QGraphicsItem.ItemIsMovable)
        self.setFlag(QGraphicsItem.ItemSendsGeometryChanges)
        self.setCacheMode(QGraphicsItem.DeviceCoordinateCache)
        self.setZValue(1)

    def boundingRect(self):
        adjust = 2.0
        return QRectF(-10 - adjust, -10 - adjust,
                      53 + adjust, 53 + adjust)

    def paint(self, painter, option, widget):
        painter.setPen(QPen(Qt.black, 0))
        painter.setBrush(Qt.darkGray)
        painter.setOpacity(0.5)
        painter.drawEllipse(-7, -7, 20, 20)
        painter.drawLine(-7, -7, 20, 20)
        painter.setOpacity(0.2)
        painter.drawRect(QRectF(QPointF(-10, -10), QPointF(20, 20)))

        # gradient = QRadialGradient(-3, -3, 10)
        # gradient.setCenter(3, 3)
        # gradient.setFocalPoint(3, 3)
        # gradient.setColorAt(1, QColor(Qt.yellow).lighter(120))
        # gradient.setColorAt(0, QColor(Qt.darkYellow).lighter(120))
        # painter.setBrush(QBrush(gradient))
        # painter.setPen(QPen(Qt.black, 0))
        # painter.drawEllipse(-10, -10, 20, 20)

    def mousePressEvent(self, event):
        self.update()
        super(Node, self).mousePressEvent(event)

    def mouseReleaseEvent(self, event):
        self.update()
        super(Node, self).mouseReleaseEvent(event)


class GraphWidget(QGraphicsView):

    def __init__(self):
        super(GraphWidget, self).__init__()

        scene = QGraphicsScene(self)
        scene.setItemIndexMethod(QGraphicsScene.NoIndex)
        scene.setSceneRect(-200, -200, 400, 400)
        self.setScene(scene)
        self.setCacheMode(QGraphicsView.CacheBackground)
        self.setViewportUpdateMode(QGraphicsView.BoundingRectViewportUpdate)
        self.setRenderHint(QPainter.Antialiasing)
        self.setTransformationAnchor(QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QGraphicsView.AnchorViewCenter)

        node1 = Node(self)
        node2 = Node(self)
        self.centerNode = Node(self)
        scene.addItem(node1)
        scene.addItem(node2)
        scene.addItem(self.centerNode)

        node1.setPos(-50, -50)
        node2.setPos(10, 10)
        self.centerNode.setPos(0, 0)

        self.lena = QPixmap("c:/pic/lena.jpg")
        self.setBackgroundBrush(QBrush(self.lena))
        self.scale(0.8, 0.8)
        self.setMinimumSize(400, 400)
        self.setWindowTitle("Zoom and Move")

    def keyPressEvent(self, event):
        key = event.key()

        if key == Qt.Key_Up:
            self.centerNode.moveBy(0, -20)
        elif key == Qt.Key_Down:
            self.centerNode.moveBy(0, 20)
        elif key == Qt.Key_Left:
            self.centerNode.moveBy(-20, 0)
        elif key == Qt.Key_Right:
            self.centerNode.moveBy(20, 0)
        elif key == Qt.Key_Plus:
            self.scaleView(1.2)
        elif key == Qt.Key_Minus:
            self.scaleView(1 / 1.2)
        elif key == Qt.Key_Space or key == Qt.Key_Enter:
            for item in self.scene().items():
                if isinstance(item, Node):
                    item.setPos(-150 + qrand() % 300, -150 + qrand() % 300)
        else:
            super(GraphWidget, self).keyPressEvent(event)

    def wheelEvent(self, event):
        self.scaleView(math.pow(2.0, -event.angleDelta().y() / 240.0))

    def scaleView(self, scaleFactor):
        factor = self.transform().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width()

        if factor < 0.07 or factor > 100:
            return

        self.scale(scaleFactor, scaleFactor)


if __name__ == "__main__":
    import sys

    app = QApplication(sys.argv)

    widget = GraphWidget()
    widget.show()

    sys.exit(app.exec_())

效果如下：

可以通过在物体上按住鼠标左键移动物体，效果如下：

多谢，我的美美。