Question

目标是将顶级TicTacToe的信号与QMainWindow类连接。

它会抛出错误：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

只有从QObject继承的类才能创建信号，例如QWidget，QMainWIndow，QGraphicsView继承自QObject，因此他们可以拥有信号。但由于效率问题，QGraphicsItem不会继承QObject，因此他们无法创建信号。如果您想要一个QObject的商品，则必须使用QGraphicsObject。此外，这些项目采用paint()方法，而不是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)

如果您仍想使用QGraphicsItem，可能的解决方法是创建一个负责通信的类，并继承自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()

Answer 2

问题是，您的班级TicTacToe不会直接或以其他方式从QObject继承，这意味着Qt无法将其用作class TicTacToe(QGraphicsObject): def __init__(self): super(TicTacToe, self).__init__()信号源。

尝试继承QGraphicsObject而不是......

SELECT
    Play_name,
    CASE WHEN  EXTRACT(HOUR FROM MAX(CASE WHEN Status = 'END' THEN Date END) - MAX(CASE WHEN Status = 'Start' THEN Date END)) < 1
         THEN 'NO'
    ELSE 'YES'
    END AS under_hour
FROM TABLENAME
GROUP BY Play_name

在PyQt中将信号连接到类之间的插槽

2 个答案: