Python Qt：可交互调整大小的QGraphicsItem，鼠标悬停区域未调整大小
我正在尝试创建一个围绕 QGraphicsRectItem（使用 PySide 或 PyQt4）的 Python 类，这个类可以通过鼠标悬停进行交互，能够移动和调整大小。除了以下问题，我几乎所有功能都已经实现：
出于某种原因，当这个项目被调整大小或移动时，鼠标悬停的区域似乎没有变化。我需要帮助解决这个问题。
也许问题出在 QGraphicsView 的 y 轴反转上：
QGraphicsView.scale(1,-1)
QGraphicsRectItem 类：
class BoxResizable(QtGui.QGraphicsRectItem):
def __init__(self, rect, parent = None, scene = None):
QtGui.QGraphicsRectItem.__init__(self, rect, parent, scene)
self.setZValue(1000)
self._rect = rect
self._scene = scene
self.mouseOver = False
self.resizeHandleSize = 4.0
self.mousePressPos = None
self.mouseMovePos = None
self.mouseIsPressed = False
self.setFlags(QtGui.QGraphicsItem.ItemIsSelectable|QtGui.QGraphicsItem.ItemIsFocusable)
self.setAcceptsHoverEvents(True)
self.updateResizeHandles()
def hoverEnterEvent(self, event):
self.updateResizeHandles()
self.mouseOver = True
self.prepareGeometryChange()
def hoverLeaveEvent(self, event):
self.mouseOver = False
self.prepareGeometryChange()
def hoverMoveEvent(self, event):
if self.topLeft.contains(event.scenePos()) or self.bottomRight.contains(event.scenePos()):
self.setCursor(QtCore.Qt.SizeFDiagCursor)
elif self.topRight.contains(event.scenePos()) or self.bottomLeft.contains(event.scenePos()):
self.setCursor(QtCore.Qt.SizeBDiagCursor)
else:
self.setCursor(QtCore.Qt.SizeAllCursor)
QtGui.QGraphicsRectItem.hoverMoveEvent(self, event)
def mousePressEvent(self, event):
"""
Capture mouse press events and find where the mosue was pressed on the object
"""
self.mousePressPos = event.scenePos()
self.mouseIsPressed = True
self.rectPress = copy.deepcopy(self._rect)
# Top left corner
if self.topLeft.contains(event.scenePos()):
self.mousePressArea = 'topleft'
# top right corner
elif self.topRight.contains(event.scenePos()):
self.mousePressArea = 'topright'
# bottom left corner
elif self.bottomLeft.contains(event.scenePos()):
self.mousePressArea = 'bottomleft'
# bottom right corner
elif self.bottomRight.contains(event.scenePos()):
self.mousePressArea = 'bottomright'
# entire rectangle
else:
self.mousePressArea = None
QtGui.QGraphicsRectItem.mousePressEvent(self, event)
def mouseReleaseEvent(self, event):
"""
Capture nmouse press events.
"""
self.mouseIsPressed = False
self.updateResizeHandles()
self.prepareGeometryChange()
QtGui.QGraphicsRectItem.mouseReleaseEvent(self, event)
def mouseMoveEvent(self, event):
"""
Handle mouse move events.
"""
self.mouseMovePos = event.scenePos()
if self.mouseIsPressed:
# Move top left corner
if self.mousePressArea=='topleft':
self._rect.setTopLeft(self.rectPress.topLeft()-(self.mousePressPos-self.mouseMovePos))
# Move top right corner
elif self.mousePressArea=='topright':
self._rect.setTopRight(self.rectPress.topRight()-(self.mousePressPos-self.mouseMovePos))
# Move bottom left corner
elif self.mousePressArea=='bottomleft':
self._rect.setBottomLeft(self.rectPress.bottomLeft()-(self.mousePressPos-self.mouseMovePos))
# Move bottom right corner
elif self.mousePressArea=='bottomright':
self._rect.setBottomRight(self.rectPress.bottomRight()-(self.mousePressPos-self.mouseMovePos))
# Move entire rectangle, don't resize
else:
self._rect.moveCenter(self.rectPress.center()-(self.mousePressPos-self.mouseMovePos))
self.updateResizeHandles()
self.prepareGeometryChange()
QtGui.QGraphicsRectItem.mousePressEvent(self, event)
def boundingRect(self):
"""
Return bounding rectangle
"""
return self._boundingRect
def updateResizeHandles(self):
"""
Update bounding rectangle and resize handles
"""
self.offset = self.resizeHandleSize*(self._scene.graphicsView.mapToScene(1,0)-self._scene.graphicsView.mapToScene(0,1)).x()
self._boundingRect = self._rect.adjusted(-self.offset, self.offset, self.offset, -self.offset)
# Note: this draws correctly on a view with an inverted y axes. i.e. QGraphicsView.scale(1,-1)
self.topLeft = QtCore.QRectF(self._boundingRect.topLeft().x(), self._boundingRect.topLeft().y() - 2*self.offset,
2*self.offset, 2*self.offset)
self.topRight = QtCore.QRectF(self._boundingRect.topRight().x() - 2*self.offset, self._boundingRect.topRight().y() - 2*self.offset,
2*self.offset, 2*self.offset)
self.bottomLeft = QtCore.QRectF(self._boundingRect.bottomLeft().x(), self._boundingRect.bottomLeft().y(),
2*self.offset, 2*self.offset)
self.bottomRight = QtCore.QRectF(self._boundingRect.bottomRight().x() - 2*self.offset, self._boundingRect.bottomRight().y(),
2*self.offset, 2*self.offset)
def paint(self, painter, option, widget):
"""
Paint Widget
"""
# show boundingRect for debug purposes
painter.setPen(QtGui.QPen(QtCore.Qt.red, 0, QtCore.Qt.DashLine))
painter.drawRect(self._boundingRect)
# Paint rectangle
painter.setPen(QtGui.QPen(QtCore.Qt.black, 0, QtCore.Qt.SolidLine))
painter.drawRect(self._rect)
# If mouse is over, draw handles
if self.mouseOver:
# if rect selected, fill in handles
if self.isSelected():
painter.setBrush(QtGui.QBrush(QtGui.QColor(0,0,0)))
painter.drawRect(self.topLeft)
painter.drawRect(self.topRight)
painter.drawRect(self.bottomLeft)
painter.drawRect(self.bottomRight)
完整代码示例：
class graphicsScene(QtGui.QGraphicsScene):
def __init__ (self, parent = None):
QtGui.QGraphicsScene.__init__(self, parent)
def setGraphicsView(self, view):
self.graphicsView = view
app = QtGui.QApplication(sys.argv)
app.setStyle('GTK')
mainWindow = QtGui.QMainWindow()
scene = graphicsScene()
scene.setSceneRect(-100,-100, 200, 200)
# Set up view properties
view = QtGui.QGraphicsView()
view.setScene(scene)
view.scale(1,-1)
view.setRenderHint(QtGui.QPainter.Antialiasing)
view.setViewportUpdateMode(QtGui.QGraphicsView.BoundingRectViewportUpdate)
view.setHorizontalScrollBarPolicy ( QtCore.Qt.ScrollBarAlwaysOff )
view.setVerticalScrollBarPolicy ( QtCore.Qt.ScrollBarAlwaysOff )
view.setUpdatesEnabled(True)
view.setMouseTracking(True)
view.setCacheMode(QtGui.QGraphicsView.CacheBackground)
view.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
scene.setGraphicsView(view)
# Add box
BoxResizable(QtCore.QRectF(-50, 50, 100.0, -100.0), parent = None, scene = scene)
mainWindow.setCentralWidget(view)
mainWindow.show()
app.exec_()
app.deleteLater()
sys.exit()
将上面的类添加到 QGraphicsScene 中，并使用反转的 y 轴 QGraphicsView，会得到如下效果：
任何帮助或建议都非常感谢！谢谢！
1 个回答
4
发现了问题的一部分：如果我在这个类里重写形状函数（也就是添加这个函数），
def shape(self):
path = QtGui.QPainterPath()
path.addRect(self.boundingRect())
return path
那么当我移动鼠标时，框的悬停区域有时候会改变大小和位置。根据文档，关于QGraphicsItem.shape()：
默认的实现会调用boundingRect()来返回一个简单的矩形形状……
这算不算是PyQt4的一个bug呢？
第二个问题：我觉得boundingRect和形状矩形的宽度和高度需要是正数？这可以通过在：
self._rect = self._rect.normalized()
中添加代码到mouseReleaseEvent函数来轻松实现。