删除所选项目上的虚线矩形

Question

我一直在尝试通过查看以下示例来更多地了解 QGraphicsView 小部件：

Toggle QPen for selected items after QGraphicsScene selection change

我发现这很有帮助，但是我注意到在选择项目时会弹出选取框。我一直在寻找摆脱这种情况的方法，似乎在 C++ 中有一个一致的答案，我在这里看到了一个例子：

https://www.qtcentre.org/threads/39659-About-QGraphicsItem-question

但我对如何将其翻译成 pyqt 感到非常困惑，所以我想知道是否有人可以从第一个链接的示例项目中提供有关如何在示例项目中执行此操作的任何见解......

我一直在通过查看如下代码来寻找可能的等价物：

https://www.riverbankcomputing.com/pipermail/pyqt/2012-November/032110.html

虽然说实话我什至不知道这些示例代码的应用是什么......

Answer 1

如果你想从 python 中的项目选择中删除矩形，你必须使用以下命令：

class GraphicsEllipseItem(QGraphicsEllipseItem):
    def paint(self, painter, option, widget):
        option.state &= ~QStyle.State_Selected
        super(GraphicsEllipseItem, self).paint(painter, option, widget)

完整的脚本

import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import random


class GraphicsEllipseItem(QGraphicsEllipseItem):
    def paint(self, painter, option, widget):
        option.state &= ~QStyle.State_Selected
        super(GraphicsEllipseItem, self).paint(painter, option, widget)


class MyGraphicsView(QGraphicsView):
    def __init__(self):
        super(MyGraphicsView, self).__init__()
        self.setDragMode(QGraphicsView.RubberBandDrag)
        self._isPanning = False
        self._mousePressed = False
        self.setCacheMode(QGraphicsView.CacheBackground)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setScene(MyGraphicsScene(self))
        self.scene().selectionChanged.connect(self.selection_changed)
        self._current_selection = []

    def select_items(self, items, on):
        pen = QPen(
            QColor(255, 255, 255) if on else QColor(255, 128, 0),
            0.5,
            Qt.SolidLine,
            Qt.RoundCap,
            Qt.RoundJoin,
        )
        for item in items:
            item.setPen(pen)

    def selection_changed(self):
        try:
            self.select_items(self._current_selection, False)
            self._current_selection = self.scene().selectedItems()
            self.select_items(self._current_selection, True)
        except RuntimeError:
            pass

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self._mousePressed = True
            if self._isPanning:
                self.setCursor(Qt.ClosedHandCursor)
                self._dragPos = event.pos()
                event.accept()
            else:
                super(MyGraphicsView, self).mousePressEvent(event)
        elif event.button() == Qt.MiddleButton:
            self._mousePressed = True
            self._isPanning = True
            self.setCursor(Qt.ClosedHandCursor)
            self._dragPos = event.pos()
            event.accept()

    def mouseMoveEvent(self, event):
        if self._mousePressed and self._isPanning:
            newPos = event.pos()
            diff = newPos - self._dragPos
            self._dragPos = newPos
            self.horizontalScrollBar().setValue(
                self.horizontalScrollBar().value() - diff.x()
            )
            self.verticalScrollBar().setValue(
                self.verticalScrollBar().value() - diff.y()
            )
            event.accept()
        else:
            super(MyGraphicsView, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            if self._isPanning:
                self.setCursor(Qt.OpenHandCursor)
            else:
                self._isPanning = False
                self.setCursor(Qt.ArrowCursor)
            self._mousePressed = False
        elif event.button() == Qt.MiddleButton:
            self._isPanning = False
            self.setCursor(Qt.ArrowCursor)
            self._mousePressed = False
        super(MyGraphicsView, self).mouseReleaseEvent(event)

    def mouseDoubleClickEvent(self, event):
        self.fitInView(self.sceneRect(), Qt.KeepAspectRatio)
        pass

    def keyPressEvent(self, event):
        if event.key() == Qt.Key_Space and not self._mousePressed:
            self._isPanning = True
            self.setCursor(Qt.OpenHandCursor)
        else:
            super(MyGraphicsView, self).keyPressEvent(event)

    def keyReleaseEvent(self, event):
        if event.key() == Qt.Key_Space:
            if not self._mousePressed:
                self._isPanning = False
                self.setCursor(Qt.ArrowCursor)
        else:
            super(MyGraphicsView, self).keyPressEvent(event)

    def wheelEvent(self, event):
        # zoom factor
        factor = 1.25

        # Set Anchors
        self.setTransformationAnchor(QGraphicsView.NoAnchor)
        self.setResizeAnchor(QGraphicsView.NoAnchor)

        # Save the scene pos
        oldPos = self.mapToScene(event.pos())

        # Zoom
        if event.delta() < 0:
            factor = 1.0 / factor
        self.scale(factor, factor)

        # Get the new position
        newPos = self.mapToScene(event.pos())

        # Move scene to old position
        delta = newPos - oldPos
        self.translate(delta.x(), delta.y())


class MyGraphicsScene(QGraphicsScene):
    def __init__(self, parent):
        super(MyGraphicsScene, self).__init__(parent)
        self.setBackgroundBrush(QBrush(QColor(50, 50, 50)))
        # self.setSceneRect(50,50,0,0)


class MyMainWindow(QMainWindow):
    def __init__(self):
        super(MyMainWindow, self).__init__()
        self.setWindowTitle("Test")
        self.resize(800, 600)
        self.gv = MyGraphicsView()
        self.setCentralWidget(self.gv)
        self.populate()

    def populate(self):
        scene = self.gv.scene()
        for i in range(500):
            x = random.randint(0, 1000)
            y = random.randint(0, 1000)
            r = random.randint(2, 8)
            rect = GraphicsEllipseItem(x, y, r, r)
            rect.setPen(
                QPen(QColor(255, 128, 0), 0.5, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin)
            )
            rect.setBrush(QBrush(QColor(255, 128, 20, 128)))
            scene.addItem(rect)
            rect.setFlag(QGraphicsItem.ItemIsSelectable)
            rect.setFlag(QGraphicsItem.ItemIsMovable)

        rect = GraphicsEllipseItem(300, 500, 20, 20)
        rect.setPen(
            QPen(QColor(255, 128, 0), 0.5, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin)
        )
        rect.setBrush(QBrush(QColor(255, 0, 0, 128)))
        scene.addItem(rect)
        rect.setFlag(QGraphicsItem.ItemIsSelectable)
        rect.setFlag(QGraphicsItem.ItemIsMovable)


def main():
    app = QApplication(sys.argv)
    ex = MyMainWindow()
    ex.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

option.state &= ~QStyle.State_Selected的解释：

state是QStyleOptionGraphicsItem的一个属性，它存储了绘画状态的信息，可能包含以下标志的组合：

在这种情况下，可以使用“|”来组合标志运算符，并使用“&~”停用。

为了更好的理解，我们用下面的例子：我们将State_Active和State_Editing中的状态设置为初始状态：

state = State_Active | State_Editing
      = 0x00010000 | 0x00400000
      = 0x00410000

并停用 State_Active 标志：

state & ~State_Active
0x00410000 & ~(0x00010000)
0x00410000 &   0xFFFEFFFF
0x00400000

如您所见，标志 State_Active 被移除而没有移除其他标志，仅通过二进制操作。

那么你想如何停用 State_Selected 标志并将其替换为必须完成的状态：

option.state = option.state & ~QStyle.State_Selected
option.state &= ~QStyle.State_Selected