本文介绍了用鼠标调整 QGraphicsItem 的大小的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
在 QGraphicsScene 中放置一个 rectangle 并使其可以用鼠标移动后，我如何使用鼠标?
After put a rectangle in a QGraphicsScene and make it movable with the mouse, how could I resize it with the mouse?
如果没有人知道答案，举个例子也不错，我正在使用 PyQt4 在 Python 中进行开发.
If no one knows an answer, a example could be good too, I'm developing in Python using PyQt4.
我知道这里有类似的问题，但他们没有分别回答我.
I know there are questions similar here, but they don't answer me respectively.
我的简化代码:
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
app = QApplication(sys.argv)
grview = QGraphicsView()
scene = QGraphicsScene()
scene.setSceneRect(0, 0, 512, 512)
scene.addPixmap(QPixmap('01.png'))
grview.setScene(scene)
item = QGraphicsRectItem(0, 0, 300, 150)
pen = QPen(Qt.darkMagenta)
pen.setWidth(4)
item.setPen(pen)
item.setFlag(QGraphicsItem.ItemIsMovable)
scene.addItem(item)
grview.fitInView(scene.sceneRect(), Qt.KeepAspectRatio)
grview.show()
sys.exit(app.exec_())
推荐答案
您需要自己实施调整大小.为此，您需要子类化 QGraphicsRectItem 并实现鼠标事件处理程序:mousePressEvent、mouseMoveEvent、mouseReleaseEvent.大体思路如下:
You would need to implement the resizing yourself. To do that you need to subclass QGraphicsRectItem and implement mouse event handlers: mousePressEvent, mouseMoveEvent, mouseReleaseEvent.The general idea is the following:
- 您创建一组可用于调整形状大小的手柄.
- 通过跟踪手柄位置变化，您可以计算形状的新几何形状.
我之前写了一些代码，它与 PyQt5 完美配合，但它也应该与 PyQt4 配合使用.您应该能够根据自己的需要进行调整:
I wrote some code times ago which was perfectly working with PyQt5, but it should work with PyQt4 too. You should be able to adapt it to you needs:
import sys
from PyQt5.QtCore import Qt, QRectF, QPointF
from PyQt5.QtGui import QBrush, QPainterPath, QPainter, QColor, QPen, QPixmap
from PyQt5.QtWidgets import QGraphicsRectItem, QApplication, QGraphicsView, QGraphicsScene, QGraphicsItem
class GraphicsRectItem(QGraphicsRectItem):
handleTopLeft = 1
handleTopMiddle = 2
handleTopRight = 3
handleMiddleLeft = 4
handleMiddleRight = 5
handleBottomLeft = 6
handleBottomMiddle = 7
handleBottomRight = 8
handleSize = +8.0
handleSpace = -4.0
handleCursors = {
handleTopLeft: Qt.SizeFDiagCursor,
handleTopMiddle: Qt.SizeVerCursor,
handleTopRight: Qt.SizeBDiagCursor,
handleMiddleLeft: Qt.SizeHorCursor,
handleMiddleRight: Qt.SizeHorCursor,
handleBottomLeft: Qt.SizeBDiagCursor,
handleBottomMiddle: Qt.SizeVerCursor,
handleBottomRight: Qt.SizeFDiagCursor,
}
def __init__(self, *args):
"""
Initialize the shape.
"""
super().__init__(*args)
self.handles = {}
self.handleSelected = None
self.mousePressPos = None
self.mousePressRect = None
self.setAcceptHoverEvents(True)
self.setFlag(QGraphicsItem.ItemIsMovable, True)
self.setFlag(QGraphicsItem.ItemIsSelectable, True)
self.setFlag(QGraphicsItem.ItemSendsGeometryChanges, True)
self.setFlag(QGraphicsItem.ItemIsFocusable, True)
self.updateHandlesPos()
def handleAt(self, point):
"""
Returns the resize handle below the given point.
"""
for k, v, in self.handles.items():
if v.contains(point):
return k
return None
def hoverMoveEvent(self, moveEvent):
"""
Executed when the mouse moves over the shape (NOT PRESSED).
"""
if self.isSelected():
handle = self.handleAt(moveEvent.pos())
cursor = Qt.ArrowCursor if handle is None else self.handleCursors[handle]
self.setCursor(cursor)
super().hoverMoveEvent(moveEvent)
def hoverLeaveEvent(self, moveEvent):
"""
Executed when the mouse leaves the shape (NOT PRESSED).
"""
self.setCursor(Qt.ArrowCursor)
super().hoverLeaveEvent(moveEvent)
def mousePressEvent(self, mouseEvent):
"""
Executed when the mouse is pressed on the item.
"""
self.handleSelected = self.handleAt(mouseEvent.pos())
if self.handleSelected:
self.mousePressPos = mouseEvent.pos()
self.mousePressRect = self.boundingRect()
super().mousePressEvent(mouseEvent)
def mouseMoveEvent(self, mouseEvent):
"""
Executed when the mouse is being moved over the item while being pressed.
"""
if self.handleSelected is not None:
self.interactiveResize(mouseEvent.pos())
else:
super().mouseMoveEvent(mouseEvent)
def mouseReleaseEvent(self, mouseEvent):
"""
Executed when the mouse is released from the item.
"""
super().mouseReleaseEvent(mouseEvent)
self.handleSelected = None
self.mousePressPos = None
self.mousePressRect = None
self.update()
def boundingRect(self):
"""
Returns the bounding rect of the shape (including the resize handles).
"""
o = self.handleSize + self.handleSpace
return self.rect().adjusted(-o, -o, o, o)
def updateHandlesPos(self):
"""
Update current resize handles according to the shape size and position.
"""
s = self.handleSize
b = self.boundingRect()
self.handles[self.handleTopLeft] = QRectF(b.left(), b.top(), s, s)
self.handles[self.handleTopMiddle] = QRectF(b.center().x() - s / 2, b.top(), s, s)
self.handles[self.handleTopRight] = QRectF(b.right() - s, b.top(), s, s)
self.handles[self.handleMiddleLeft] = QRectF(b.left(), b.center().y() - s / 2, s, s)
self.handles[self.handleMiddleRight] = QRectF(b.right() - s, b.center().y() - s / 2, s, s)
self.handles[self.handleBottomLeft] = QRectF(b.left(), b.bottom() - s, s, s)
self.handles[self.handleBottomMiddle] = QRectF(b.center().x() - s / 2, b.bottom() - s, s, s)
self.handles[self.handleBottomRight] = QRectF(b.right() - s, b.bottom() - s, s, s)
def interactiveResize(self, mousePos):
"""
Perform shape interactive resize.
"""
offset = self.handleSize + self.handleSpace
boundingRect = self.boundingRect()
rect = self.rect()
diff = QPointF(0, 0)
self.prepareGeometryChange()
if self.handleSelected == self.handleTopLeft:
fromX = self.mousePressRect.left()
fromY = self.mousePressRect.top()
toX = fromX + mousePos.x() - self.mousePressPos.x()
toY = fromY + mousePos.y() - self.mousePressPos.y()
diff.setX(toX - fromX)
diff.setY(toY - fromY)
boundingRect.setLeft(toX)
boundingRect.setTop(toY)
rect.setLeft(boundingRect.left() + offset)
rect.setTop(boundingRect.top() + offset)
self.setRect(rect)
elif self.handleSelected == self.handleTopMiddle:
fromY = self.mousePressRect.top()
toY = fromY + mousePos.y() - self.mousePressPos.y()
diff.setY(toY - fromY)
boundingRect.setTop(toY)
rect.setTop(boundingRect.top() + offset)
self.setRect(rect)
elif self.handleSelected == self.handleTopRight:
fromX = self.mousePressRect.right()
fromY = self.mousePressRect.top()
toX = fromX + mousePos.x() - self.mousePressPos.x()
toY = fromY + mousePos.y() - self.mousePressPos.y()
diff.setX(toX - fromX)
diff.setY(toY - fromY)
boundingRect.setRight(toX)
boundingRect.setTop(toY)
rect.setRight(boundingRect.right() - offset)
rect.setTop(boundingRect.top() + offset)
self.setRect(rect)
elif self.handleSelected == self.handleMiddleLeft:
fromX = self.mousePressRect.left()
toX = fromX + mousePos.x() - self.mousePressPos.x()
diff.setX(toX - fromX)
boundingRect.setLeft(toX)
rect.setLeft(boundingRect.left() + offset)
self.setRect(rect)
elif self.handleSelected == self.handleMiddleRight:
print("MR")
fromX = self.mousePressRect.right()
toX = fromX + mousePos.x() - self.mousePressPos.x()
diff.setX(toX - fromX)
boundingRect.setRight(toX)
rect.setRight(boundingRect.right() - offset)
self.setRect(rect)
elif self.handleSelected == self.handleBottomLeft:
fromX = self.mousePressRect.left()
fromY = self.mousePressRect.bottom()
toX = fromX + mousePos.x() - self.mousePressPos.x()
toY = fromY + mousePos.y() - self.mousePressPos.y()
diff.setX(toX - fromX)
diff.setY(toY - fromY)
boundingRect.setLeft(toX)
boundingRect.setBottom(toY)
rect.setLeft(boundingRect.left() + offset)
rect.setBottom(boundingRect.bottom() - offset)
self.setRect(rect)
elif self.handleSelected == self.handleBottomMiddle:
fromY = self.mousePressRect.bottom()
toY = fromY + mousePos.y() - self.mousePressPos.y()
diff.setY(toY - fromY)
boundingRect.setBottom(toY)
rect.setBottom(boundingRect.bottom() - offset)
self.setRect(rect)
elif self.handleSelected == self.handleBottomRight:
fromX = self.mousePressRect.right()
fromY = self.mousePressRect.bottom()
toX = fromX + mousePos.x() - self.mousePressPos.x()
toY = fromY + mousePos.y() - self.mousePressPos.y()
diff.setX(toX - fromX)
diff.setY(toY - fromY)
boundingRect.setRight(toX)
boundingRect.setBottom(toY)
rect.setRight(boundingRect.right() - offset)
rect.setBottom(boundingRect.bottom() - offset)
self.setRect(rect)
self.updateHandlesPos()
def shape(self):
"""
Returns the shape of this item as a QPainterPath in local coordinates.
"""
path = QPainterPath()
path.addRect(self.rect())
if self.isSelected():
for shape in self.handles.values():
path.addEllipse(shape)
return path
def paint(self, painter, option, widget=None):
"""
Paint the node in the graphic view.
"""
painter.setBrush(QBrush(QColor(255, 0, 0, 100)))
painter.setPen(QPen(QColor(0, 0, 0), 1.0, Qt.SolidLine))
painter.drawRect(self.rect())
painter.setRenderHint(QPainter.Antialiasing)
painter.setBrush(QBrush(QColor(255, 0, 0, 255)))
painter.setPen(QPen(QColor(0, 0, 0, 255), 1.0, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
for handle, rect in self.handles.items():
if self.handleSelected is None or handle == self.handleSelected:
painter.drawEllipse(rect)
def main():
app = QApplication(sys.argv)
grview = QGraphicsView()
scene = QGraphicsScene()
scene.setSceneRect(0, 0, 680, 459)
scene.addPixmap(QPixmap('01.png'))
grview.setScene(scene)
item = GraphicsRectItem(0, 0, 300, 150)
scene.addItem(item)
grview.fitInView(scene.sceneRect(), Qt.KeepAspectRatio)
grview.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
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