调整 QGraphicsRectItem 的大小和重新绘制的 PyQt 问题

Posted 2023-02-17

【中文标题】调整 QGraphicsRectItem 的大小和重新绘制的 PyQt 问题

【英文标题】：PyQt issue with resizing and repainting of QGraphicsRectItem

【发布时间】：2019-03-21 17:43:48

【问题描述】：

我正在尝试创建一个可调整大小的 QGraphicsRectItem，并带有选择不同绘制样式的选项。

如果我创建一个仅具有调整大小功能的简单矩形，那么它会按预期工作：

class Rectangle(QtWidgets.QGraphicsRectItem):
    def __init__(self, x, y, w, h):
        super(Rectangle, self).__init__(0, 0, w, h)
        self.setPen(QtGui.QPen(QtCore.Qt.red, 2))
        self.setFlags(QtWidgets.QGraphicsItem.ItemIsSelectable
            | QtWidgets.QGraphicsItem.ItemIsMovable
            | QtWidgets.QGraphicsItem.ItemIsFocusable
            | QtWidgets.QGraphicsItem.ItemSendsGeometryChanges
            | QtWidgets.QGraphicsItem.ItemSendsScenePositionChanges)
        self.setPos(QtCore.QPointF(x, y))

        self.rect = rect = QtCore.QRectF(0, 0, 200, 200)

    def boundingRect(self):
        return self.rect.adjusted(-10, -10, 10, 10)

    def mouseMoveEvent(self, event):
        if event.buttons() & QtCore.Qt.LeftButton:
            super(Rectangle, self).mouseMoveEvent(event)
        if event.buttons() & QtCore.Qt.RightButton:
            self.rect = QtCore.QRectF(QtCore.QPoint(), event.pos()).normalized()
            self.prepareGeometryChange()
            self.setRect(self.rect)

---

当我尝试修改它以更改笔样式和颜色（如果处于活动状态）时，它变得无法选择且无法聚焦。不仅如此，边界矩形出乎意料地消失了。这是修改后的版本：

class Rectangle(QtWidgets.QGraphicsRectItem):
    def __init__(self, position, scene, style=QtCore.Qt.SolidLine,
                 rect=None, matrix=QtGui.QMatrix()):
        super(Rectangle, self).__init__()

        # self.setPen(QtGui.QPen(QtCore.Qt.red, 2))
        self.setFlags(QtWidgets.QGraphicsItem.ItemIsSelectable
                      | QtWidgets.QGraphicsItem.ItemIsMovable
                      | QtWidgets.QGraphicsItem.ItemIsFocusable
                      | QtWidgets.QGraphicsItem.ItemSendsGeometryChanges
                      | QtWidgets.QGraphicsItem.ItemSendsScenePositionChanges)

        if rect is None:
            rect = QtCore.QRectF(0, 0, 200, 200)

        self.size = QtCore.QPointF(200, 200)
        self.rect = rect
        self.style = style
        self.setPos(position)
        self.setMatrix(matrix)

        scene.clearSelection()
        scene.addItem(self)
        self.setSelected(True)
        self.setFocus()
        global RAW
        RAW = True

        self.pen = QtGui.QPen(self.style)
        self.pen.setColor(QtCore.Qt.black)
        self.pen.setWidth(1)

    def parentWidget(self):
        return self.scene().views()[0]

    def boundingRect(self):
        return self.rect.adjusted(-10, -10, 10, 10)

    def paint(self, painter, option, widget):
        if option.state & QtWidgets.QStyle.State_Selected:
            self.pen.setColor(QtCore.Qt.blue)

        painter.setPen(self.pen)
        painter.drawRect(self.rect)

    def itemChange(self, change, variant):
        if change != QtWidgets.QGraphicsItem.ItemSelectedChange:
            global RAW
            RAW = True
        return QtWidgets.QGraphicsItem.itemChange(self, change, variant)

    def contextMenuEvent(self, event):
        wrapped = []
        menu = QtWidgets.QMenu(self.parentWidget())
        for text, param in (("&Solid", QtCore.Qt.SolidLine),
                            ("&Dashed", QtCore.Qt.DashLine),
                            ("D&otted", QtCore.Qt.DotLine),
                            ("D&ashDotted", QtCore.Qt.DashDotLine),
                            ("DashDo&tDotten", QtCore.Qt.DashDotDotLine)):
            wrapper = functools.partial(self.setStyle, param)
            wrapped.append(wrapper)
            menu.addAction(text, wrapper)
        menu.exec_(event.screenPos())

    def setStyle(self, style):
        #self.prepareGeometryChange()
        self.style = style
        self.update()
        global RAW
        RAW = True

    def mousePressEvent(self, event):
        if event.buttons() & QtCore.Qt.LeftButton:
            super(Rectangle, self).mouseMoveEvent(event)
        if event.buttons() & QtCore.Qt.MiddleButton:
            if self.isSelected():
                self.rect = QtCore.QRectF(QtCore.QPoint(), event.pos()).normalized()
                self.prepareGeometryChange()
                self.setRect(self.rect)

            global RAW
            RAW = True

我猜主要问题在于重新实现的 paint() 函数，但我仍然没有想出任何想法 在哪里 ...

谁能解释我做错了什么？ 哪里出错了，如何让这个东西正常工作？

【参考方案1】：

我的触摸板上没有中间按钮，所以我用右键实现了逻辑，但我给出了一个 10 像素的小边缘，您可以在其中更改矩形的大小。

要更改样式，您只需更改 QGraphicsItem 的 QPen。

import functools
from PyQt5 import QtCore, QtGui, QtWidgets

class Rectangle(QtWidgets.QGraphicsRectItem):
    def __init__(self, x, y, w, h):
        super(Rectangle, self).__init__(0, 0, w, h)
        self.setPen(QtGui.QPen(QtCore.Qt.red, 2))
        self.setFlags(QtWidgets.QGraphicsItem.ItemIsSelectable
            | QtWidgets.QGraphicsItem.ItemIsMovable
            | QtWidgets.QGraphicsItem.ItemIsFocusable
            | QtWidgets.QGraphicsItem.ItemSendsGeometryChanges
            | QtWidgets.QGraphicsItem.ItemSendsScenePositionChanges)
        self.setPos(QtCore.QPointF(x, y))

    def mouseMoveEvent(self, event):
        if event.buttons() & QtCore.Qt.LeftButton:
            super(Rectangle, self).mouseMoveEvent(event)
        if event.buttons() & QtCore.Qt.RightButton:
            rect = QtCore.QRectF(QtCore.QPoint(), event.pos()).normalized()
            self.prepareGeometryChange()
            self.setRect(rect)

    def contextMenuEvent(self, event):
        super(Rectangle, self).contextMenuEvent(event)
        delta = 10
        r = self.boundingRect()
        r.adjust(delta, delta, -delta, -delta)
        if not r.contains(event.pos()):
            return
        self.setSelected(True)
        wrapped = []
        menu = QtWidgets.QMenu(self.parentWidget())
        for text, param in (("&Solid", QtCore.Qt.SolidLine),
                            ("&Dashed", QtCore.Qt.DashLine),
                            ("D&otted", QtCore.Qt.DotLine),
                            ("D&ashDotted", QtCore.Qt.DashDotLine),
                            ("DashDo&tDotten", QtCore.Qt.DashDotDotLine)):
            wrapper = functools.partial(self.setStyle, param)
            wrapped.append(wrapper)
            menu.addAction(text, wrapper)
        menu.exec_(event.screenPos())

    def paint(self, painter, option, widget):
        painter.setPen(self.pen())
        painter.setBrush(self.brush())
        if option.state & QtWidgets.QStyle.State_Selected:
            pen = self.pen()
            pen.setColor(QtCore.Qt.blue)
            painter.setPen(pen)
            painter.setBrush(QtCore.Qt.NoBrush)
        painter.drawRect(self.boundingRect())

    def setStyle(self, style):
        pen = self.pen()
        pen.setStyle(style)
        self.setPen(pen)

if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    scene = QtWidgets.QGraphicsScene(-400, -400, 800, 800)
    w = QtWidgets.QGraphicsView(scene)
    scene.addItem(Rectangle(100, 100, 100, 100))
    w.show()
    sys.exit(app.exec_())