使用pyqt5逐步绘制的正确方法

Question

我有一个基本上是一个圆的小部件。我想逐步画，所以我需要画在步骤（imo）。在

通过下面的代码，我已经实现了我想要的。但是，有一个问题。我将一个新事件传递给paintEvent函数，因为如果我不这样做，图像在所有事情都完成之前不会更新，所以我什么都没有实现。在

小部件代码

import sys
import time
from PyQt5.QtCore import Qt, QRect
from PyQt5.QtWidgets import QApplication, QWidget, QCheckBox, QDesktopWidget

from PyQt5.QtGui import QPen, QPainter, QPaintEvent, QConicalGradient, QColor, QBrush

class Circle(QWidget):

    def __init__(self, size, color):
        super().__init__()

        self.loadingAngle = 0
        self.width = 0
        self.color = color
        self.pixmap_opacity = 1

        self.resize(size, size);
        self.center()

        self.initUI()

    def initUI(self):

        self.width = 15
        self.loadingAngle = 0
        self.show()

    def center(self):
        qr = self.frameGeometry()
        cp = QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)
        self.move(qr.topLeft())

    def paintEvent(self, qevent):

        self.setWindowFlags(Qt.FramelessWindowHint)
        self.setAttribute(Qt.WA_TranslucentBackground)
        self.setStyleSheet("background:transparent;")

        drawingRect = QRect()
        drawingRect.setX(qevent.rect().x() + self.width)
        drawingRect.setY(qevent.rect().y() + self.width)
        drawingRect.setWidth(qevent.rect().width() - self.width * 2)
        drawingRect.setHeight(qevent.rect().height() - self.width * 2)

        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)

        gradient = QConicalGradient()
        gradient.setCenter(drawingRect.center())
        gradient.setAngle(90)
        gradient.setColorAt(1, QColor(0,0,0))
        gradient.setColorAt(0, QColor(self.color[0], self.color[1],self.color[2]))

        arcLengthApproximation = self.width + self.width / 3
        pen = QPen(QBrush(gradient), self.width)
        pen.setCapStyle(Qt.RoundCap)
        painter.setPen(pen)
        painter.drawArc(drawingRect, 90 * 16 - arcLengthApproximation, -self.loadingAngle * 16)
        #time.sleep(0.25)

        if self.loadingAngle < 360:
            self.loadingAngle += 1
            #self.paintEvent(QDrawEvent())
            self.paintEvent(QPaintEvent())

有问题的线路

^{pr2}$

这一行产生了几个错误，但即使有了它们，我也会做我想做的。在

1. 如果我将qevent从函数本身传递给这个新调用，那么图像不会像我之前说的那样得到更新。

2. 如果我创建这个新的QPaintEvent，它确实可以工作。但是，错误是：

Traceback (most recent call last):

File "/home/btc/Escritorio/SinestesiaRCB/Clases/Widget.py", line 68, in paintEvent self.paintEvent(QPaintEvent())

TypeError: arguments did not match any overloaded call: QPaintEvent(QRegion): not enough arguments

QPaintEvent(QRect): not enough arguments

QPaintEvent(QPaintEvent): not enough arguments

QBackingStore::endPaint() called with active painter on backingstore paint device

这些错误可能来自其他行，如：

qevent.rect().x()

因为新事件是空的。在

所以基本上我的问题是，我应该怎样做才能使它正确，也就是说，实现我想要的而不出错？在

我所说的渐进式。这已经完成了创建几个小部件，每一个都在前一个小部件之后一秒钟。在

Answer 1

永远不要直接调用paintEvent，必须使用update()间接调用它。另一方面，如果您希望每隔一段时间被调用，那么在本例中应该使用QTimer或更好的QTimeLine。在

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class Circle(QtWidgets.QWidget):
    def __init__(self, size, color):
        super().__init__()
        self._loading_angle = 0
        self.width = 0
        self.color = color
        self.pixmap_opacity = 1
        self.resize(size, size)
        self.setWindowFlags(QtCore.Qt.FramelessWindowHint)
        self.setAttribute(QtCore.Qt.WA_TranslucentBackground)
        self.setStyleSheet("background:transparent;")
        self.center()
        self.initUI()

        timeline = QtCore.QTimeLine(4000, self)
        timeline.setFrameRange(0, 360)
        timeline.frameChanged.connect(self.setLoadingAngle)
        timeline.start()

    def initUI(self):
        self.width = 15
        self.setLoadingAngle(0)
        self.show()

    def loadingAngle(self):
        return self._loading_angle

    def setLoadingAngle(self, angle):
        self._loading_angle = angle
        self.update()

    loadingAngle = QtCore.pyqtProperty(int, fget=loadingAngle, fset=setLoadingAngle)

    def center(self):
        qr = self.frameGeometry()
        cp = QtWidgets.QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)
        self.move(qr.topLeft())

    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        painter.setRenderHint(QtGui.QPainter.Antialiasing)
        drawingRect  = QtCore.QRect(QtCore.QPoint(), self.rect().size() - 2*self.width*QtCore.QSize(1, 1))
        drawingRect.moveCenter(self.rect().center())

        gradient = QtGui.QConicalGradient()
        gradient.setCenter(drawingRect.center())
        gradient.setAngle(90)
        gradient.setColorAt(1, QtGui.QColor(0,0,0))
        gradient.setColorAt(0, self.color)
        arcLengthApproximation = self.width + self.width / 3
        pen = QtGui.QPen(QtGui.QBrush(gradient), self.width)
        pen.setCapStyle(QtCore.Qt.RoundCap)
        painter.setPen(pen)
        painter.drawArc(drawingRect, 90 * 16 - arcLengthApproximation, -self._loading_angle * 16)


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = Circle(400, QtGui.QColor("blue"))
    w.show()
    sys.exit(app.exec_())