将信号连接到 PyQt 中类之间的槽

Question

目的是将顶级类的信号TicTacToe与 QMainWindow 类连接。

它抛出一个错误：TicTacToe cannot be converted to PyQt5.QtCore.QObject in this context

#!/usr/bin/env python


from PyQt5.QtCore import (QLineF, QPointF, QRectF, pyqtSignal)
from PyQt5.QtGui import (QIcon, QBrush, QColor, QPainter, QPixmap)
from PyQt5.QtWidgets import (QAction, QMainWindow, QApplication, QGraphicsView, QGraphicsScene, QGraphicsItem,
                             QGridLayout, QVBoxLayout, QHBoxLayout,
                             QLabel, QLineEdit, QPushButton)

class TicTacToe(QGraphicsItem):
    def __init__(self):
        super(TicTacToe, self).__init__()

    def paintEvent(self, painter, option, widget):
        painter.setPen(Qt.black)
        painter.drawLine(0,100,300,100)


    def boundingRect(self):
        return QRectF(0,0,300,300)

    def mousePressEvent(self, event):
        pos = event.pos()
        self.select(int(pos.x()/100), int(pos.y()/100))
        self.update()
        super(TicTacToe, self).mousePressEvent(event)

    messageSignal = pyqtSignal(int)


class MyGraphicsView(QGraphicsView):
    def __init__(self):
        super(MyGraphicsView, self).__init__()
        scene = QGraphicsScene(self)
        self.tic_tac_toe = TicTacToe()
        scene.addItem(self.tic_tac_toe)

        scene.addPixmap(QPixmap("exit.png"))

        self.setScene(scene)

    def keyPressEvent(self, event):
        key = event.key()
        if key == Qt.Key_R:
            self.tic_tac_toe.reset()
        super(MyGraphicsView, self).keyPressEvent(event)

class Example(QMainWindow):    
    def __init__(self):
        super(Example, self).__init__()

        self.y = MyGraphicsView()
        self.setCentralWidget(self.y)

        self.y.tic_tac_toe.messageSignal.connect (self.messageSlot)

        self.initUI()

    def messageSlot(self, val):
        self.statusBar().showMessage(val)


    def initUI(self):               
        self.toolbar = self.addToolBar('Tools')


        self.setGeometry(30, 30, 30, 20)
        self.setWindowTitle('Menubar')    
        self.show()        


if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    mainWindow = Example()

    mainWindow.showFullScreen()
    sys.exit(app.exec_())

Answer 1

只有继承自的类才QObject能够创建信号，例如QWidget、QMainWIndow、QGraphicsView继承自QObject，因此它们可以拥有信号。但QGraphicsItem不继承，QObject因为效率问题所以不具备创建信号的能力。如果你想要一个QObject你必须使用的物品QGraphicsObject。另外，物品有paint()方法，没有paintEvent()。

class TicTacToe(QGraphicsObject):
    def paint(self, painter, option, widget):
        painter.setPen(Qt.black)
        painter.drawLine(0,100,300,100)

    def boundingRect(self):
        return QRectF(0,0,300,300)

    def mousePressEvent(self, event):
        pos = event.pos()
        # self.select(int(pos.x()/100), int(pos.y()/100))
        self.update()
        super(TicTacToe, self).mousePressEvent(event)

    messageSignal = pyqtSignal(int)

如果您仍然想使用QGraphicsItem，一个可能的解决方法是创建一个负责通信并继承自的类QObject：

class Helper(QObject):
    messageSignal = pyqtSignal(int)

class TicTacToe(QGraphicsObject):
    def __init__(self, helper):
        super(TicTacToe, self).__init__()
        self.helper = helper

    def paint(self, painter, option, widget):
        painter.setPen(Qt.black)
        painter.drawLine(0,100,300,100)

    def boundingRect(self):
        return QRectF(0,0,300,300)

    def mousePressEvent(self, event):
        pos = event.pos()
        self.helper.emit(10)
        # self.select(int(pos.x()/100), int(pos.y()/100))
        self.update()
        super(TicTacToe, self).mousePressEvent(event)


class MyGraphicsView(QGraphicsView):
    def __init__(self):
        super(MyGraphicsView, self).__init__()
        scene = QGraphicsScene(self)
        self.helper = Helper(self)
        self.tic_tac_toe = TicTacToe(self.helper)
        scene.addItem(self.tic_tac_toe)
        scene.addPixmap(QPixmap("exit.png"))
        self.setScene(scene)

    def keyPressEvent(self, event):
        key = event.key()
        if key == Qt.Key_R:
            self.tic_tac_toe.reset()
        super(MyGraphicsView, self).keyPressEvent(event)

class Example(QMainWindow):    
    def __init__(self):
        super(Example, self).__init__()

        self.y = MyGraphicsView()
        self.setCentralWidget(self.y)
        self.helper.messageSignal.connect(self.messageSlot)
        self.initUI()

    def messageSlot(self, val):
        self.statusBar().showMessage(val)


    def initUI(self):               
        self.toolbar = self.addToolBar('Tools')
        self.setGeometry(30, 30, 30, 20)
        self.setWindowTitle('Menubar')    
        self.show()