python - 更改 Pen 不会更新外部线程中的 QGraphicsLineItem

Question

我正在通过在 QGraphicsLine 的子类中编程的方法来更新笔的颜色，甚至是 QGraphicsLine 对象的笔。问题在于，当我设置新笔时，当我从线程调用它时，该行消失了。

import sys
from PyQt5.QtGui import QColor, QBrush, QPen, QPainter
from PyQt5.QtWidgets import QGraphicsScene, QGraphicsEllipseItem, QGraphicsSceneMouseEvent, \
    QGraphicsSceneHoverEvent, QGraphicsLineItem, QApplication, QMainWindow, QGraphicsView, QToolBar, QAction
from threading import Thread
from time import sleep
from random import randint


class GraphicsLine(QGraphicsLineItem):
    def __init__(self, x1: float, y1: float, x2: float, y2: float):
        super(GraphicsLine, self).__init__(x1, y1, x2, y2)

        pen = QPen(QColor(0, 0, 0))
        pen.setWidth(5)
        self.setPen(pen)
        self.setZValue(5)

    def change_color(self):
        pen = QPen(QColor(randint(0, 255), randint(0, 255), randint(0, 255)))
        pen.setWidth(5)
        self.setPen(pen)


class GraphicsNode(QGraphicsEllipseItem):
    def __init__(self, x: float, y: float, size: int):
        super(GraphicsNode, self).__init__(x - size/2, y - size/2, size, size)
        self.setAcceptHoverEvents(True)
        self.setZValue(10)
        brush = QBrush(QColor(0, 0, 0))
        pen = QPen(QColor(0, 0, 0))
        pen.setWidth(0)
        self.setBrush(brush)
        self.setPen(pen)

    def mousePressEvent(self, event: QGraphicsSceneMouseEvent) -> None:
        pass

    def hoverEnterEvent(self, event: QGraphicsSceneHoverEvent) -> None:
        self.setBrush(QColor(0, 255, 0))

    def hoverLeaveEvent(self, event: QGraphicsSceneHoverEvent) -> None:
        self.setBrush(QColor(0, 0, 0))


class MainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.width = 600
        self.height = 500
        self.thread_stop = False

        self.toolbar = QToolBar()
        self.action_color = QAction('Change Color', self)
        self.action_color.triggered.connect(self.__change_color)
        self.toolbar.addAction(self.action_color)
        self.action_stop = QAction('Stop Thread', self)
        self.action_stop.triggered.connect(self.__stop_thread)
        self.toolbar.addAction(self.action_stop)
        self.addToolBar(self.toolbar)

        self.scene = QGraphicsScene()
        self.graphics_view = QGraphicsView(self.scene, self)
        self.graphics_view.setRenderHints(QPainter.Antialiasing | QPainter.HighQualityAntialiasing)
        self.graphics_view.setGeometry(0, 20, 600, 500)
        self.__create_graphs()
        self.show()

    def __create_graphs(self):
        self.nodes = [GraphicsNode(0, 0, 20), GraphicsNode(0, 100, 20)]
        self.lines = [GraphicsLine(0, 0, 0, 100)]
        for node in self.nodes:
            self.scene.addItem(node)
        for line in self.lines:
            self.scene.addItem(line)
        self.thread = Thread(target=self.__color_changer_thread)
        self.thread.start()

    def __color_changer_thread(self):
        while not self.thread_stop:
            for line in self.lines:
                line.change_color()
            sleep(5)

    def __change_color(self):
        for line in self.lines:
            line.change_color()

    def __stop_thread(self):
        self.thread_stop = True


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

    window = MainWindow()
    app.exec_()

单击 ToolBar 中的 Action 时对象 GraphicsLine 的颜色会发生变化，但是线程使该项目不可见。如果对线程进行了评论，则操作底部会毫无问题地更改颜色。

先感谢您。

标签： pythonqtpyqt5

Answer 1

非常感谢@musicamante。

解决方案 该解决方案包括创建一个 QThread 而不是 POSIX 线程，并在 QThread 子类中创建一个信号并将其连接到在 Widget 中创建的插槽。（参考：从后台工作线程修改 Qt GUI）

import sys
from PyQt5.QtCore import QThread, pyqtSlot, pyqtSignal
from PyQt5.QtGui import QColor, QBrush, QPen, QPainter
from PyQt5.QtWidgets import QGraphicsScene, QGraphicsEllipseItem, QGraphicsSceneMouseEvent, \
    QGraphicsSceneHoverEvent, QGraphicsLineItem, QApplication, QMainWindow, QGraphicsView, QToolBar, QAction
from threading import Thread
from time import sleep
from random import randint


class ColorChangingThread(QThread):
    signal_color_change = pyqtSignal(int, name='Scheduled color change')

    def __init__(self):
        super(ColorChangingThread, self).__init__()
        self.stop_thread = False

    def run(self) -> None:
        while not self.stop_thread:
            self.signal_color_change.emit(0)
            self.sleep(5)


class GraphicsLine(QGraphicsLineItem):
    def __init__(self, x1: float, y1: float, x2: float, y2: float):
        super(GraphicsLine, self).__init__(x1, y1, x2, y2)

        pen = QPen(QColor(0, 0, 0))
        pen.setWidth(5)
        self.setPen(pen)
        self.setZValue(5)

    def change_color(self):
        pen = QPen(QColor(randint(0, 255), randint(0, 255), randint(0, 255)))
        pen.setWidth(5)
        self.setPen(pen)


class GraphicsNode(QGraphicsEllipseItem):
    def __init__(self, x: float, y: float, size: int):
        super(GraphicsNode, self).__init__(x - size/2, y - size/2, size, size)
        self.setAcceptHoverEvents(True)
        self.setZValue(10)
        brush = QBrush(QColor(0, 0, 0))
        pen = QPen(QColor(0, 0, 0))
        pen.setWidth(0)
        self.setBrush(brush)
        self.setPen(pen)

    def mousePressEvent(self, event: QGraphicsSceneMouseEvent) -> None:
        pass

    def hoverEnterEvent(self, event: QGraphicsSceneHoverEvent) -> None:
        self.setBrush(QColor(0, 255, 0))

    def hoverLeaveEvent(self, event: QGraphicsSceneHoverEvent) -> None:
        self.setBrush(QColor(0, 0, 0))


class MainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.width = 600
        self.height = 500
        self.thread = ColorChangingThread()
        self.thread.signal_color_change.connect(self.slot_color_change)

        self.toolbar = QToolBar()
        self.action_color = QAction('Change Color', self)
        self.action_color.triggered.connect(self.__change_color)
        self.toolbar.addAction(self.action_color)
        self.action_stop = QAction('Stop Thread', self)
        self.action_stop.triggered.connect(self.__stop_thread)
        self.toolbar.addAction(self.action_stop)
        self.addToolBar(self.toolbar)

        self.scene = QGraphicsScene()
        self.graphics_view = QGraphicsView(self.scene, self)
        self.graphics_view.setRenderHints(QPainter.Antialiasing | QPainter.HighQualityAntialiasing)
        self.graphics_view.setGeometry(0, 20, 600, 500)
        self.__create_graphs()
        self.show()

    def __create_graphs(self):
        self.nodes = [GraphicsNode(0, 0, 20), GraphicsNode(0, 100, 20)]
        self.lines = [GraphicsLine(0, 0, 0, 100)]
        for node in self.nodes:
            self.scene.addItem(node)
        for line in self.lines:
            self.scene.addItem(line)
        self.thread.start()

    @pyqtSlot(int)
    def slot_color_change(self, value):
        print('Received signal with value %d' % value)
        self.__change_color()

    def __change_color(self):
        for line in self.lines:
            line.change_color()

    def __stop_thread(self):
        self.thread.stop_thread = True


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

    window = MainWindow()
    app.exec_()