在 QGraphicsScene 选择更改后为所选项目切换 QPen答案

【问题标题】：Toggle QPen for selected items after QGraphicsScene selection change在 QGraphicsScene 选择更改后为所选项目切换 QPen
【发布时间】：2018-05-20 10:35:48
【问题描述】：

如何切换所选图形视图项目的 QPen 颜色？理想情况下，我想在图形视图或图形场景对象中处理这种颜色变化，而不是直接在主窗口选择事件中处理它。

感谢任何帮助。目前，选择对象时，它会转动笔色白色。我不确定如何将其转回以避免循环遍历所有对象。

有没有一种方法可以在 MyGraphicsView 类本身中添加一个函数来处理图表中任何和所有选定项目的笔颜色变化？

更新：更多详细信息 以下是我正在尝试解决的选择问题列表：

当用户单击并选择矩形时，它应该取消选择所有项目，将它们恢复为默认的笔颜色。新选择的项目应该是白色的笔颜色。如果用户正在控制它应该添加新选择的项目。如果项目已被选中并且矩形跨越它们，它仍应保持它们处于选中状态。
如果用户在光标下没有出现任何项目的负区域单击，它应该清除当前选择。
如果用户单击某个项目，则应选择该项目并将 Pen 颜色设为白色。
如果用户保持控制，则应始终添加到选择中。

代码

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


class MyGraphicsView(QGraphicsView):
    def __init__(self):
        super(MyGraphicsView, self).__init__()
        self.setDragMode(QGraphicsView.RubberBandDrag)
        self._isPanning = False
        self._mousePressed = False
        # self.setBackgroundBrush(QImage("C:/Users/jmartini/Desktop/Temp/images/flag_0140.jpg"))
        self.setCacheMode(QGraphicsView.CacheBackground)
        self.setHorizontalScrollBarPolicy( Qt.ScrollBarAlwaysOff )
        self.setVerticalScrollBarPolicy( Qt.ScrollBarAlwaysOff )


    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__()
        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.gv.setScene(MyGraphicsScene(self))
        self.setCentralWidget(self.gv)

        self.gv.scene().selectionChanged.connect(self.selection_changed)
        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 = scene.addEllipse(x, y, r, r, QPen(QColor(255,128,0), 0.5, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin), QBrush(QColor(255,128,20,128)))
            rect.setFlag( QGraphicsItem.ItemIsSelectable )
            rect.setFlag( QGraphicsItem.ItemIsMovable )

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


    def selection_changed(self):
        selection = self.gv.scene().selectedItems()
        print 'Selected:', len(selection)
        for i in selection:
            i.setPen(QPen(QColor(255,255,255), 0.5, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))


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


if __name__ == '__main__':
    main()

【问题讨论】：

你能解释一下吗
据我了解，如果您选择了一个项目，请将您的 QPen 更改为白色，如果您重新选择相同的项目，您应该返回到以前的状态。我是对的？
当项目被选中时，它会变为白色，如果取消选择该项目，它应该会恢复到原来的颜色。

标签： python selection pyside qgraphicsview qgraphicsscene

【解决方案1】：

应该可以通过缓存最后一个选择然后在进行新选择之前清除它来获得所需的行为：

class MyGraphicsView(QGraphicsView):
    def __init__(self):
        ...
        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

这是完整的脚本：

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


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__()
        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 = scene.addEllipse(x, y, r, r, QPen(QColor(255,128,0), 0.5, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin), QBrush(QColor(255,128,20,128)))
            rect.setFlag( QGraphicsItem.ItemIsSelectable )
            rect.setFlag( QGraphicsItem.ItemIsMovable )

        rect = scene.addEllipse(300, 500, 20, 20, QPen(QColor(255,128,0), 0.5, Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin), QBrush(QColor(255,0,0,128)))
        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()

【讨论】：

这部分有效。使用“拖动选择”矩形时似乎没有更新，并且仅在我选择该项目两次时才有效。除非我单击它两次，否则它不会将颜色切换回原来的颜色。
@JokerMartini。嗯 - 你没有在你的问题中提到任何这些额外的要求。在我尝试其他解决方案之前，您能否确保提供所有您期望的行为的详细信息？
我当然可以这样做 :)，这是我的错，因为我假设其他人会知道我期望应用默认选择行为。
@JokerMartini。我看到您添加了一个小编辑，但它并没有真正澄清任何事情。例如，当拖动一个选择矩形时，如果它包含处于混合状态的项目，您究竟希望发生什么？通过 ctrl-click 进行多选时也会出现类似的情况。
@JokerMartini。我已经用新的解决方案更新了我的答案。它似乎工作正常，但我还没有对它进行破坏测试......