python - 在 QGraphicsScene 选择更改后为所选项目切换 QPen

Question

如何为选定的图形 View 项目切换 QPen 颜色？理想情况下，我想在图形 View 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，当对象被选中时，它会将笔颜色变为白色。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:更详细的信息以下是我试图解决的选择问题列表:

1. 当用户点击并选择一个矩形时，它应该取消选择所有项目，将它们恢复为默认的笔颜色。新选择的项目应该有一个白色的笔颜色。如果用户持有控制权，则应添加新选择的项目。如果项目已经被选中并且矩形穿过它们，它应该仍然保持选中状态。
2. 如果用户点击光标下没有任何项目的负区域，则应清除当前选择。
3. 如果用户点击一个项目，它应该选择它并将笔颜色设为白色。
4. 如果用户持有控制权，则应始终将其添加到选择中。

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()

Answer 1

应该可以通过缓存最后一次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

完整的脚本如下:

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()