QGraphicsItem在移动后未停留在原位

时间:2019-01-26 14:39:11

标签: python pyqt pyqt5 qgraphicsscene qgraphicsrectitem

我当前正在创建一个使用QGraphicsView的应用程序,该应用程序允许用户移动QGraphicsItems,以便它们可以创建类似图的结构。

我需要这些项目在单击时改变颜色,但是在释放鼠标按钮时变回其原始颜色。但是,当我定义“ mouseReleaseEvent()”方法时,当我在移动视口后单击视口中的任何位置时,该项只是恢复到原始位置。

第一次移动物品后如何使它留在原处?

为了更好地控制项目的位置,我尝试对场景使用“ setSceneRect()”,但是并不能解决问题。

我也无法使用CustomItem的“ setPos()”方法解决问题。当同一场景中有多个项目时,似乎坐标系发生了变化。

另一个问题是,当鼠标悬停在其他项目上时,其他一些项目应更改颜色。我尝试覆盖CustomItem类中的“ hoverEnterEvent()”方法,但无法正常工作。

这里是用于重现我所面临问题的最少代码。

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(QtWidgets.QMainWindow):

    def __init__(self):
        QtWidgets.QMainWindow.__init__(self)
        self.setupUi(self)

        self.main_menu = self.menuBar().addMenu("&Menu") 
        self.addItem = QtWidgets.QAction("&Add Rectangle", self, triggered = self.addRectangle)
        self.delItem = QtWidgets.QAction("&Delete Selected Rectangle(s)", self, triggered = self.delRectangle) 
        self.main_menu.addAction(self.addItem) 
        self.main_menu.addAction(self.delItem) 


        self.scene = CustomScene(self.main_menu) 
        self.graphicsView.setScene(self.scene)

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.verticalLayout = QtWidgets.QVBoxLayout(self.centralwidget)
        self.verticalLayout.setObjectName("verticalLayout")
        self.graphicsView = QtWidgets.QGraphicsView(self.centralwidget)
        self.graphicsView.setObjectName("graphicsView")
        self.verticalLayout.addWidget(self.graphicsView)
        MainWindow.setCentralWidget(self.centralwidget)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))

    def addRectangle(self):
        self.item = CustomItem()
        self.scene.addItem(self.item)
        self.scene.update()

    def delRectangle(self):
        for item in self.scene.selectedItems():
            self.scene.removeItem(item)

class CustomScene (QtWidgets.QGraphicsScene):

    def __init__(self, scene_menu, parent=None):
        super(CustomScene, self).__init__(parent)

        self.setSceneRect(0,0,750,500)
        self.sceneMenu = scene_menu

    def contextMenuEvent (self, event):
        self.sceneMenu.exec_(event.screenPos()) 

class CustomItem (QtWidgets.QGraphicsRectItem):

    def __init__(self, parent = None, scene = None):
        super(CustomItem, self).__init__()

        self.setFlag(QtWidgets.QGraphicsItem.ItemIsMovable, True) 
        self.setFlag(QtWidgets.QGraphicsItem.ItemIsSelectable, True) 

        self.setRect(200,200,120,25) #Creates and show the rectangle

    def contextMenuEvent(self, event): #Defines the menu shown on mouse right-click
        self.scene().clearSelection()
        self.setSelected(True)
        self.RCMenu.exec_(event.screenPos()) 

    def mousePressEvent(self, event):
        self.setBrush(QtGui.QBrush(QtCore.Qt.cyan))

    def hoverEnterEvent(self, event): #Not Working as intended, but it should change the rectangle's color to lightGray when I hover the mouse over it
        self.setBrush(QtGui.QBrush(QtCore.Qt.lightGray))

    def mouseReleaseEvent(self, event): # HERE IS THE REAL PROBLEM. WHENEVER I CLICK ON THE RECTANGLE AFTER IT'S RELEASE, IT GOES TO A SEEMINGLY RANDOM LOCATION
        self.setBrush(QtGui.QBrush(QtCore.Qt.white))

if __name__ == "__main__":
    import sys

    if not QtWidgets.QApplication.instance():
        app = QtWidgets.QApplication(sys.argv)

    else:
        app = QtWidgets.QApplication.instance()

    window = Ui_MainWindow()
    window.show()
    sys.exit(app.exec_())

1 个答案:

答案 0 :(得分:1)

QGraphicsItem已经具有移到新位置的行为,但是当您由于删除父类的实现而覆盖这些行为时,如果要保留该行为,则必须调用的方法。通过super的父类。

另一方面,您必须使用setAcceptHoverEvents(True)启用悬停类型的事件。

使用上述解决方案是:

class CustomItem (QtWidgets.QGraphicsRectItem):
    def __init__(self, parent = None, scene = None):
        super(CustomItem, self).__init__()
        self.setAcceptHoverEvents(True)
        self.setFlag(QtWidgets.QGraphicsItem.ItemIsMovable, True) 
        self.setFlag(QtWidgets.QGraphicsItem.ItemIsSelectable, True) 
        self.setRect(200,200,120,25) #Creates and show the rectangle

    def contextMenuEvent(self, event): #Defines the menu shown on mouse right-click
        self.scene().clearSelection()
        self.setSelected(True)
        self.RCMenu.exec_(event.screenPos()) 

    def mousePressEvent(self, event):
        self.setBrush(QtGui.QBrush(QtCore.Qt.cyan))
        super(CustomItem, self).mousePressEvent(event)

    def mouseReleaseEvent(self, event):
        self.setBrush(QtGui.QBrush(QtCore.Qt.white))
        super(CustomItem, self).mouseReleaseEvent(event)

    def hoverEnterEvent(self, event):
        self.setBrush(QtGui.QBrush(QtCore.Qt.lightGray))
        super(CustomItem, self).hoverEnterEvent(event)

    def hoverLeaveEvent(self, event):
        self.setBrush(QtGui.QBrush(QtCore.Qt.white))
        super(CustomItem, self).hoverLeaveEvent(event)

另一方面,用于删除项目的代码中存在一个问题,但现在不可见,因为到目前为止,您仅删除一个元素,但是当您要删除一组元素时,您会看到问题是,当您从列表中删除项目时,您必须从头到尾排在最后,因为如果您在访问未分配的内存时没有问题,那么解决方案是:

def delRectangle(self):
    for item in reversed(self.scene.selectedItems()):
        self.scene.removeItem(item)