PyQtGraph中的图形在缩放后不会更新

Question

我有以下PyQtGraph程序，它使一个红色方块＆＃34;移动＆＃34;移动滑块时：

import sys

from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWidgets import QSlider
from pyqtgraph import (
    mkBrush,
    mkPen,
    GraphicsObject,
    QtGui,
    PlotWidget,
)


class SquareItem(GraphicsObject):
    def __init__(self):
        super().__init__()
        self.position_picture = QtGui.QPicture()

    def paint(self, p, *args):
        p.drawPicture(0, 0, self.position_picture)

    def boundingRect(self):
        return QtCore.QRectF(-5, -5, 20, 10)

    def update_position(self, x):
        self.position_picture = QtGui.QPicture()
        painter = QtGui.QPainter(self.position_picture)
        painter.scale(1, -1)
        painter.setBrush(mkBrush('r'))
        painter.setPen(mkPen(None))
        painter.drawRect(QtCore.QRectF(x, 0, 1, 1))
        painter.end()
        self.informViewBoundsChanged()


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.setWindowTitle('Micromouse maze simulator')
        self.resize(600, 600)

        frame = QtWidgets.QFrame()
        layout = QtWidgets.QVBoxLayout(frame)

        self.graphics = PlotWidget()
        self.graphics.setAspectLocked()
        self.item = SquareItem()
        self.graphics.addItem(self.item)

        self.slider = QSlider(QtCore.Qt.Horizontal)
        self.slider.setSingleStep(1)
        self.slider.setPageStep(10)
        self.slider.setRange(0, 10)
        self.slider.setTickPosition(QSlider.TicksAbove)
        self.slider.valueChanged.connect(self.slider_value_changed)
        self.slider.setValue(1)

        layout.addWidget(self.graphics)
        layout.addWidget(self.slider)

        self.setCentralWidget(frame)

    def slider_value_changed(self, value):
        self.item.update_position(value)


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

一切似乎都运行正常，但是如果我放大/缩小然后再次移动滑块，方形位置就不再更新（即：不重新绘制正方形）。

我该如何解决？

更新

• 我使用方块来简化问题。实际上，我不仅要改变位置，还可以绘制不同的形状，因此使用setPos()并不是一种选择。

Answer 1

如果要更改位置，则不应更新绘画，只应使用setPos()。 paint()函数将boundingRect()作为参考，因此在移动图表时，您将在该坐标系中移动它而不是PlotWidget的坐标系。

class SquareItem(GraphicsObject):
    def paint(self, p, *args):
        p.setBrush(mkBrush('r'))
        p.setPen(mkPen(None))
        p.drawRect(self.boundingRect())

    def boundingRect(self):
        return QtCore.QRectF(0, 0, 1, 1)

    def update_position(self, x):
        self.setPos(x, 0)


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.setWindowTitle('Micromouse maze simulator')
        self.resize(600, 600)

        frame = QtWidgets.QFrame()
        layout = QtWidgets.QVBoxLayout(frame)

        self.graphics = PlotWidget()
        self.graphics.setAspectLocked()
        self.item = SquareItem()
        self.graphics.addItem(self.item)

        self.graphics.setRange(rect=QtCore.QRectF(-10, -10, 20, 20))

        self.slider = QSlider(QtCore.Qt.Horizontal)
        self.slider.setSingleStep(1)
        self.slider.setPageStep(10)
        self.slider.setRange(0, 10)
        self.slider.setTickPosition(QSlider.TicksAbove)
        self.slider.valueChanged.connect(self.slider_value_changed)
        self.slider.setValue(1)

        layout.addWidget(self.graphics)
        layout.addWidget(self.slider)

        self.setCentralWidget(frame)

    def slider_value_changed(self, value):
        self.item.update_position(value)

如果您不打算使用信号，建议使用继承自QGraphicsItem而非QGraphicsObject的对象，例如您可以使用QGraphicsRectItem：

import sys

from PyQt5 import QtCore, QtWidgets
from pyqtgraph import (
    mkBrush,
    mkPen,
    GraphicsObject,
    QtGui,
    PlotWidget,
)

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.setWindowTitle('Micromouse maze simulator')
        self.resize(600, 600)

        frame = QtWidgets.QFrame()
        layout = QtWidgets.QVBoxLayout(frame)

        self.graphics = PlotWidget()
        self.graphics.setAspectLocked()
        self.item = QtWidgets.QGraphicsRectItem(0, 0, 1, 1)
        self.item.setBrush(mkBrush('r'))
        self.item.setPen(mkPen(None))
        self.graphics.addItem(self.item)

        self.graphics.setRange(rect=QtCore.QRectF(-10, -10, 20, 20))

        self.slider = QtWidgets.QSlider(QtCore.Qt.Horizontal)
        self.slider.setSingleStep(1)
        self.slider.setPageStep(10)
        self.slider.setRange(0, 10)
        self.slider.setTickPosition(QtWidgets.QSlider.TicksAbove)
        self.slider.valueChanged.connect(self.slider_value_changed)
        self.slider.setValue(1)

        layout.addWidget(self.graphics)
        layout.addWidget(self.slider)

        self.setCentralWidget(frame)

    def slider_value_changed(self, value):
        self.item.setPos(value, 0)


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

<强>更新

如果您想重新绘制，请致电update()：

import sys

from PyQt5 import QtCore, QtWidgets

from pyqtgraph import (
    mkBrush,
    mkPen,
    GraphicsObject,
    QtGui,
    PlotWidget,
)


class SquareItem(GraphicsObject):
    colors = ['r', 'g', 'b', 'c', 'm', 'y', 'k', 'w', 'FF0', 'AA0', '0AA']
    def __init__(self):
        super().__init__()
        self.mColor = SquareItem.colors[0]

    def paint(self, p, *args):
        p.setBrush(mkBrush(self.mColor))
        p.setPen(mkPen(None))
        p.drawRect(self.boundingRect())

    def boundingRect(self):
        return QtCore.QRectF(0, 0, 1, 1)

    def update_draw(self, x):
        self.mColor = SquareItem.colors[x]
        self.update()


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.setWindowTitle('Micromouse maze simulator')
        self.resize(600, 600)

        frame = QtWidgets.QFrame()
        layout = QtWidgets.QVBoxLayout(frame)

        self.graphics = PlotWidget()
        self.graphics.setAspectLocked()
        self.item = SquareItem()
        self.graphics.addItem(self.item)

        self.graphics.setRange(rect=QtCore.QRectF(-10, -10, 20, 20))

        self.slider = QtWidgets.QSlider(QtCore.Qt.Horizontal)
        self.slider.setSingleStep(1)
        self.slider.setPageStep(10)
        self.slider.setRange(0, 10)
        self.slider.setTickPosition(QtWidgets.QSlider.TicksAbove)
        self.slider.valueChanged.connect(self.item.update_draw)
        self.slider.setValue(1)

        layout.addWidget(self.graphics)
        layout.addWidget(self.slider)

        self.setCentralWidget(frame)

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