本例原是PyQt4版本的官方demo 程序,现已改成了PyQt5版本。程序可响应用户的键盘操作,如方向键,“+”,“-”键和空格键,以及鼠标拖放和滚轮操作。其功能是模拟弹性节点网络----节点小球在收到外力时会移动,在外力撤除后会回弹。
代码如下:
import math
from PyQt5.QtCore import (qAbs, QLineF, QPointF, qrand, QRectF, QSizeF, qsrand,
Qt, QTime)
from PyQt5.QtGui import (QBrush, QColor, QLinearGradient, QPainter,
QPainterPath, QPen, QPolygonF, QRadialGradient)
from PyQt5.QtWidgets import (QApplication, QGraphicsItem, QGraphicsScene,
QGraphicsView, QStyle)
class Edge(QGraphicsItem):#边线图形项
Pi = math.pi
TwoPi = 2.0 * Pi
Type = QGraphicsItem.UserType + 2
def __init__(self, sourceNode, destNode):
super(Edge, self).__init__()
self.arrowSize = 10.0
self.sourcePoint = QPointF()
self.destPoint = QPointF()
self.setAcceptedMouseButtons(Qt.NoButton)
self.source = sourceNode #起始节点
self.dest = destNode #终节点
self.source.addEdge(self)
self.dest.addEdge(self)
self.adjust()
def type(self):
return Edge.Type
def sourceNode(self):
return self.source
def setSourceNode(self, node):
self.source = node
self.adjust()
def destNode(self):
return self.dest
def setDestNode(self, node):
self.dest = node
self.adjust()
def adjust(self):
if not self.source or not self.dest:
return
line = QLineF(self.mapFromItem(self.source, 0, 0),
self.mapFromItem(self.dest, 0, 0))
length = line.length()
self.prepareGeometryChange()
if length > 20.0:
edgeOffset = QPointF((line.dx() * 10) / length,
(line.dy() * 10) / length)
self.sourcePoint = line.p1() + edgeOffset
self.destPoint = line.p2() - edgeOffset
else:
self.sourcePoint = line.p1()
self.destPoint = line.p1()
def boundingRect(self):
if not self.source or not self.dest:
return QRectF()
penWidth = 1.0
extra = (penWidth + self.arrowSize) / 2.0
return QRectF(self.sourcePoint,
QSizeF(self.destPoint.x() - self.sourcePoint.x(),
self.destPoint.y() - self.sourcePoint.y())).normalized().adjusted(-extra, -extra, extra, extra)
def paint(self, painter, option, widget):
if not self.source or not self.dest:
return
# Draw the line itself.
line = QLineF(self.sourcePoint, self.destPoint)
if line.length() == 0.0:
return
painter.setPen(QPen(Qt.black, 1, Qt.SolidLine, Qt.RoundCap,
Qt.RoundJoin))
painter.drawLine(line)
# Draw the arrows if there's enough room.
angle = math.acos(line.dx() / line.length())
if line.dy() >= 0:
angle = Edge.TwoPi - angle
sourceArrowP1 = self.sourcePoint + QPointF(math.sin(angle + Edge.Pi / 3) * self.arrowSize,
math.cos(angle + Edge.Pi / 3) * self.arrowSize)
sourceArrowP2 = self.sourcePoint + QPointF(math.sin(angle + Edge.Pi - Edge.Pi / 3) * self.arrowSize,
math.cos(angle + Edge.Pi - Edge.Pi / 3) * self.arrowSize);
destArrowP1 = self.destPoint + QPointF(math.sin(angle - Edge.Pi / 3) * self.arrowSize,
math.cos(angle - Edge.Pi / 3) * self.arrowSize)
destArrowP2 = self.destPoint + QPointF(math.sin(angle - Edge.Pi + Edge.Pi / 3) * self.arrowSize,
math.cos(angle - Edge.Pi + Edge.Pi / 3) * self.arrowSize)
painter.setBrush(Qt.black)
painter.drawPolygon(QPolygonF([line.p1(), sourceArrowP1, sourceArrowP2]))
painter.drawPolygon(QPolygonF([line.p2(), destArrowP1, destArrowP2]))
class Node(QGraphicsItem):#节点小球图形项
Type = QGraphicsItem.UserType + 1
def __init__(self, graphWidget):
super(Node, self).__init__()
self.graph = graphWidget
self.edgeList = []
self.newPos = QPointF()
self.setFlag(QGraphicsItem.ItemIsMovable)
self.setFlag(QGraphicsItem.ItemSendsGeometryChanges)
self.setCacheMode(QGraphicsItem.DeviceCoordinateCache)
self.setZValue(1)
def type(self):
return Node.Type
def addEdge(self, edge):
self.edgeList.append(edge)
edge.adjust()
def edges(self):
return self.edgeList
def calculateForces(self):
if not self.scene() or self.scene().mouseGrabberItem() is self:
self.newPos = self.pos()
return
# Sum up all forces pushing this item away.
xvel = 0.0
yvel = 0.0
for item in self.scene().items():
if not isinstance(item, Node):
continue
line = QLineF(self.mapFromItem(item, 0, 0), QPointF(0, 0))
dx = line.dx()
dy = line.dy()
l = 2.0 * (dx * dx + dy * dy)
if l > 0:
xvel += (dx * 150.0) / l
yvel += (dy * 150.0) / l
# Now subtract all forces pulling items together.
weight = (len(self.edgeList) + 1) * 10.0
for edge in self.edgeList:
if edge.sourceNode() is self:
pos = self.mapFromItem(edge.destNode(), 0, 0)
else:
pos = self.mapFromItem(edge.sourceNode(), 0, 0)
xvel += pos.x() / weight
yvel += pos.y() / weight
if qAbs(xvel) < 0.1 and qAbs(yvel) < 0.1:
xvel = yvel = 0.0
sceneRect = self.scene().sceneRect()
self.newPos = self.pos() + QPointF(xvel, yvel)
self.newPos.setX(min(max(self.newPos.x(), sceneRect.left() + 10), sceneRect.right() - 10))
self.newPos.setY(min(max(self.newPos.y(), sceneRect.top() + 10), sceneRect.bottom() - 10))
def advance(self):
if self.newPos == self.pos():
return False
self.setPos(self.newPos)
return True
def boundingRect(self):
adjust = 2.0
return QRectF(-10 - adjust, -10 - adjust, 23 + adjust, 23 + adjust)
def shape(self):
path = QPainterPath()
path.addEllipse(-10, -10, 20, 20)
return path
def paint(self, painter, option, widget):
painter.setPen(Qt.NoPen)
painter.setBrush(Qt.darkGray)
painter.drawEllipse(-7, -7, 20, 20)
gradient = QRadialGradient(-3, -3, 10)
if option.state & QStyle.State_Sunken:
gradient.setCenter(3, 3)
gradient.setFocalPoint(3, 3)
gradient.setColorAt(1, QColor(Qt.yellow).lighter(120))
gradient.setColorAt(0, QColor(Qt.darkYellow).lighter(120))
else:
gradient.setColorAt(0, Qt.yellow)
gradient.setColorAt(1, Qt.darkYellow)
painter.setBrush(QBrush(gradient))
painter.setPen(QPen(Qt.black, 0))
painter.drawEllipse(-10, -10, 20, 20)
def itemChange(self, change, value):
if change == QGraphicsItem.ItemPositionHasChanged:
for edge in self.edgeList:
edge.adjust()
self.graph.itemMoved()
return super(Node, self).itemChange(change, value)
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):#图形视图类
def __init__(self):
super(GraphWidget, self).__init__()
self.timerId = 0
scene = QGraphicsScene(self)#场景
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)
#创建个节点视图项
node1 = Node(self)
node2 = Node(self)
node3 = Node(self)
node4 = Node(self)
self.centerNode = Node(self)
node6 = Node(self)
node7 = Node(self)
node8 = Node(self)
node9 = Node(self)
#将各节点加入场景
scene.addItem(node1)
scene.addItem(node2)
scene.addItem(node3)
scene.addItem(node4)
scene.addItem(self.centerNode)
scene.addItem(node6)
scene.addItem(node7)
scene.addItem(node8)
scene.addItem(node9)
#生成各边线视图项,并将其加入场景
scene.addItem(Edge(node1, node2))
scene.addItem(Edge(node2, node3))
scene.addItem(Edge(node2, self.centerNode))
scene.addItem(Edge(node3, node6))
scene.addItem(Edge(node4, node1))
scene.addItem(Edge(node4, self.centerNode))
scene.addItem(Edge(self.centerNode, node6))
scene.addItem(Edge(self.centerNode, node8))
scene.addItem(Edge(node6, node9))
scene.addItem(Edge(node7, node4))
scene.addItem(Edge(node8, node7))
scene.addItem(Edge(node9, node8))
node1.setPos(-50, -50)
node2.setPos(0, -50)
node3.setPos(50, -50)
node4.setPos(-50, 0)
self.centerNode.setPos(0, 0)
node6.setPos(50, 0)
node7.setPos(-50, 50)
node8.setPos(0, 50)
node9.setPos(50, 50)
self.scale(0.8, 0.8)
self.setMinimumSize(400, 400)
self.setWindowTitle("Elastic Nodes")
def itemMoved(self):
if not self.timerId:
self.timerId = self.startTimer(1000 / 25)
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 timerEvent(self, event):
nodes = [item for item in self.scene().items() if isinstance(item, Node)]
for node in nodes:
node.calculateForces()
itemsMoved = False
for node in nodes:
if node.advance():
itemsMoved = True
if not itemsMoved:
self.killTimer(self.timerId)
self.timerId = 0
def wheelEvent(self, event):
self.scaleView(math.pow(2.0, -event.angleDelta().y() / 240.0))
def drawBackground(self, painter, rect):
# Shadow.
sceneRect = self.sceneRect()
rightShadow = QRectF(sceneRect.right(), sceneRect.top() + 5, 5,
sceneRect.height())
bottomShadow = QRectF(sceneRect.left() + 5, sceneRect.bottom(),
sceneRect.width(), 5)
if rightShadow.intersects(rect) or rightShadow.contains(rect):
painter.fillRect(rightShadow, Qt.darkGray)
if bottomShadow.intersects(rect) or bottomShadow.contains(rect):
painter.fillRect(bottomShadow, Qt.darkGray)
# Fill.
gradient = QLinearGradient(sceneRect.topLeft(), sceneRect.bottomRight())
gradient.setColorAt(0, Qt.white)
gradient.setColorAt(1, Qt.lightGray)
painter.fillRect(rect.intersected(sceneRect), QBrush(gradient))
painter.setBrush(Qt.NoBrush)
painter.drawRect(sceneRect)
# Text.
textRect = QRectF(sceneRect.left() + 4, sceneRect.top() + 4,
sceneRect.width() - 4, sceneRect.height() - 4)
message = "Click and drag the nodes around, and zoom with the " \
"mouse wheel or the '+' and '-' keys"
font = painter.font()
font.setBold(True)
font.setPointSize(14)
painter.setFont(font)
painter.setPen(Qt.lightGray)
painter.drawText(textRect.translated(2, 2), message)
painter.setPen(Qt.black)
painter.drawText(textRect, message)
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)
qsrand(QTime(0,0,0).secsTo(QTime.currentTime()))
widget = GraphWidget()
widget.show()
sys.exit(app.exec_())
qAbs()返回一个数的绝对值。
qsrand用来设置一个种子,该种子为qrand生成随机数的起始值。比如说qsrand(10),设置10为种子,那么qrand生成的随机数就在[10,32767]之间。而如果在qrand()前没有调用过qsrand(),那么qrand()就会自动调用qsrand(1),即系统默认将1作为随机数的起始值。使用相同的种子生成的随机数一样。
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