QGraphicsItem 仅在选择父项时可见

Question

我正在尝试模仿类似于您在 Photoshop 中看到的路径编辑，它以这种方式交互......

1. 您选择路径，它的点变得可见
2. 用户可以点击并拖动Path的任意Point项，来调整Path
3. 当用户直接单击并拖动路径时，它会移动路径
4. 取消选择路径后，点将再次隐藏

我遇到问题的地方是

1. 取消选择路径时隐藏点，但编辑所选样条线的点时不隐藏

这是我所拥有的：

这是我试图匹配的内容的参考：

import sys
import math
import random

from PySide2 import QtWidgets, QtGui, QtCore

# SETTINGS
handle_size = 16
handle_color = QtGui.QColor(40,130,230)
handle_radius = 8


class AnnotationPointItem(QtWidgets.QGraphicsEllipseItem):
    def __init__(self, positionFlag=0, pos=QtCore.QPointF(), parent=None):
        super(AnnotationPointItem, self).__init__(-handle_radius, -handle_radius, 2*handle_radius, 2*handle_radius, parent)
        
        self.setFlags(QtWidgets.QGraphicsItem.ItemIsMovable | QtWidgets.QGraphicsItem.ItemIsSelectable | QtWidgets.QGraphicsItem.ItemSendsScenePositionChanges)    
        self.setPen(QtGui.QPen(handle_color, 4, QtCore.Qt.SolidLine))
        self.setBrush(QtGui.QBrush(QtGui.QColor('white')))
        self.positionFlag = positionFlag 


    def paint(self, painter, option, widget=None):
        # Remove the selection outline
        # if self.isSelected():
        #     option.state &= ~QtWidgets.QStyle.State_Selected

        super(AnnotationPointItem, self).paint(painter, option, widget)


    # def mousePressEvent(self, event):
    #     # Handle the event, but don't propagate to the parent
    #     # event.accept()
    #     print('clicked....')
    #     return super(AnnotationPointItem, self).mousePressEvent(event)


    def itemChange(self, change, value):
        # print(change, self.isSelected())
        if change == QtWidgets.QGraphicsItem.ItemPositionChange:
            # print('ItemPositionChange')
            pass
        elif change == QtWidgets.QGraphicsItem.ItemPositionHasChanged:
            # print('ItemPositionHasChanged')
            parent = self.parentItem()
            if parent:
                # Get the position of the cursor in the view's coordinates
                if self.positionFlag == 0:
                    parent.setPoints(start=self.pos())
                elif self.positionFlag == 1:
                    parent.setPoints(end=self.pos())
        elif change == QtWidgets.QGraphicsItem.ItemSelectedChange:
            pass
        return super(AnnotationPointItem, self).itemChange(change, value)


class AnnotationPathItem(QtWidgets.QGraphicsLineItem):
    def __init__(self, 
        start=QtCore.QPointF(), 
        end=QtCore.QPointF(), 
        color=QtCore.Qt.green,
        thickness=10,
        parent=None):
        super(AnnotationPathItem, self).__init__(start.x(), start.y(), end.x(), end.y(), parent)

        self._color = color
        self._thickness = thickness

        self.setFlags(QtWidgets.QGraphicsItem.ItemIsMovable | QtWidgets.QGraphicsItem.ItemIsSelectable)
        self.setPen(QtGui.QPen(self._color, self._thickness, QtCore.Qt.SolidLine))

        # child items
        self.startPointItem = AnnotationPointItem(positionFlag=0, parent=self)
        self.startPointItem.hide()
        self.startPointItem.setPos(self.line().p1())

        self.endPointItem = AnnotationPointItem(positionFlag=1, parent=self)
        self.endPointItem.hide()
        self.endPointItem.setPos(self.line().p2())


    def itemChange(self, change, value):
        if change == QtWidgets.QGraphicsItem.ItemSelectedChange:
            self.selectionChanged(value)
        return super(AnnotationPathItem, self).itemChange(change, value)


    def selectionChanged(self, selected):
        # Implement what you want to do when the selection changes
        print(self.startPointItem.isSelected(), self.endPointItem.isSelected())
        if selected or self.startPointItem.isSelected() or self.endPointItem.isSelected():
            self.startPointItem.show()
            self.endPointItem.show()
        # else:
        #     self.startPointItem.hide()
        #     self.endPointItem.hide()


    def paint(self, painter, option, widget=None):
        # Remove the selection outline
        if self.isSelected():
            option.state &= ~QtWidgets.QStyle.State_Selected

        super(AnnotationPathItem, self).paint(painter, option, widget)


    def setPoints(self, start=None, end=None):
        currentLine = self.line()
        if start != None:
            currentLine.setP1(start)
        if end != None:
            currentLine.setP2(end)
        self.setLine(currentLine)


class MainWindow(QtWidgets.QWidget):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.resize(1200,1200)

        self.scene = QtWidgets.QGraphicsScene(self)
        self.scene.setBackgroundBrush(QtGui.QColor(40,40,40))

        self.view = QtWidgets.QGraphicsView(self)
        self.view.setSceneRect(-4000, -4000, 8000, 8000)
        self.view.setRenderHints(QtGui.QPainter.Antialiasing | QtGui.QPainter.SmoothPixmapTransform)
        self.view.setMouseTracking(True)
        self.view.setScene(self.scene)

        self.addButton = QtWidgets.QPushButton("Add Annotation", self)
        self.addButton.clicked.connect(self.add_annotation)

        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.view)
        layout.addWidget(self.addButton)
        self.setLayout(layout)

        # samples
        item = AnnotationPathItem(QtCore.QPointF(-70, -150), QtCore.QPointF(150, -350))
        self.scene.addItem(item)


    def add_annotation(self):
        r = random.randint(0,255)
        g = random.randint(0,255)
        b = random.randint(0,255)
        color = QtGui.QColor(r,g,b)
        startPos = QtCore.QPointF(random.randint(-200,200), random.randint(-200,200))
        endPos = QtCore.QPointF(random.randint(-200,200), random.randint(-200,200))
        item = AnnotationPathItem(startPos, endPos, color)
        self.scene.addItem(item)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = MainWindow()
    window.show()
    app.exec_()

Answer 1

您无法通过检查项目的选择更改来实现此目的，因为当按下鼠标时选择一个项目时，视图已经取消选择所有其他项目。

相反，您可以使用场景的

selectionChanged

信号（该信号在所有选择更改完成时发出），并决定是否显示项目。由于项目通常不是首先使用场景创建的，因此您必须在

ItemSceneChange

项目更改时连接到信号：

    def itemChange(self, change, value):
        if change == QGraphicsItem.ItemSceneChange:
            if self.scene():
                self.scene().selectionChanged.disconnect(
                    self.updateChildSelection)
            if value:
                value.selectionChanged.connect(self.updateChildSelection)
        return super(AnnotationPathItem, self).itemChange(change, value)

    def updateChildSelection(self):
        selection = set(self.scene().selectedItems())
        showItems = bool(
            set((self, self.startPointItem, self.endPointItem)) & selection
        )
        self.startPointItem.setVisible(showItems)
        self.endPointItem.setVisible(showItems)