qpainter 渐变进度条

以下是使用QPainter实现渐变进度条的代码示例：

from PyQt5.QtWidgets import QApplication, QWidget, QProgressBar
from PyQt5.QtGui import QPainter, QBrush, QLinearGradient
from PyQt5.QtCore import Qt

class MyProgressBar(QProgressBar):
    def paintEvent(self, event):
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing) # 抗锯齿
        painter.setPen(Qt.NoPen) # 无边框
        painter.fillRect(self.rect(), Qt.white) # 填充白色背景

        # 设置渐变色
        gradient = QLinearGradient(0, 0, self.width(), 0)
        gradient.setColorAt(0.0, Qt.red)
        gradient.setColorAt(0.5, Qt.yellow)
        gradient.setColorAt(1.0, Qt.green)
        painter.setBrush(QBrush(gradient))

        # 计算进度条的宽度
        progress_width = int(self.width() * self.value() / self.maximum())

        # 绘制进度条
        painter.drawRect(0, 0, progress_width, self.height())

if __name__ == '__main__':
    app = QApplication([])
    window = QWidget()
    window.resize(400, 100)
    progress_bar = MyProgressBar(window)
    progress_bar.setGeometry(20, 20, 360, 60)
    progress_bar.setRange(0, 100)
    progress_bar.setValue(50)
    window.show()
    app.exec_()