Qt画环状图的几种简单方法

1、红色圆环
代码部分

void MainWindow::paintEvent(QPaintEvent* event)
{
    QPainter painter(this);
    painter.save();
    //设置反锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::Qt4CompatiblePainting);
    QRect drawRect = event->rect();
    QRegion region(drawRect.adjusted(10,10,-10,-10),QRegion::Ellipse);
    drawRect.setSize(QSize(drawRect.width()/2,drawRect.height()/2));
    drawRect.moveTopLeft(QPoint((event->rect().width() - drawRect.width())/2,(event->rect().height() - drawRect.height())/2));
    QRegion region2(drawRect,QRegion::Ellipse);
    QPainterPath painterPath;
    painterPath.addRegion(region.subtracted(region2));
    painter.fillPath(painterPath,Qt::red);
    event->accept();
    painter.restore();
}

2

代码部分

void MainWindow::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.save();
    //设置反锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform| QPainter::Qt4CompatiblePainting);
    QRect drawRect = event->rect();
    QRegion region(drawRect.adjusted(8,8,-8,-8),QRegion::Ellipse);
    drawRect.setSize(QSize(drawRect.width()/2,drawRect.height()/2));
    drawRect.moveTopLeft(QPoint((event->rect().width() - drawRect.width())/2,(event->rect().height() - drawRect.height())/2));
        QRegion region2(drawRect,QRegion::Ellipse);
        painter.setClipRegion(region.subtracted(region2));
        painter.fillRect(region.boundingRect(),Qt::yellow);
        event->accept();
        painter.restore();




}

3、在圆的中心画一个与背景颜色相同的园

代码：

void MainWindow::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.save();
    //设置反锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::Qt4CompatiblePainting);
    QRect drawRect = event->rect();
    painter.setBrush(Qt::yellow);
    painter.drawEllipse(drawRect.adjusted(10,10,-10,-10));
    painter.setBrush(painter.background());
    painter.drawEllipse(drawRect.adjusted(drawRect.width()/4,drawRect.height()/4,-drawRect.width()/4,-drawRect.height()/4));
    event->accept();
    painter.restore();
}

4、采用线型渐变，在中心位置到内环半径位置为透明，环部分为颜色值。这里的半径位置在线形渐变中用比例表示，这种只能画圆环，椭圆环不行

代码部分：

void MainWindow::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.save();
    //设置反锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::Qt4CompatiblePainting);
    QRect drawRect = event->rect();
    QRadialGradient rg(drawRect.center(),drawRect.width()/2,drawRect.center());
    rg.setColorAt(0,Qt::transparent);
    rg.setColorAt(0.6,Qt::transparent);
    rg.setColorAt(0.61,Qt::blue);
    rg.setColorAt(1,Qt::blue);
    painter.setBrush(rg);
    painter.drawEllipse(drawRect);
    event->accept();
    painter.restore();
}

5、画一个饼图，中间显示百分比

代码部分：

QPainter p(this);
    p.setRenderHint(QPainter::Antialiasing);
    int m_persent = 56;//绘制的环的比例
    int m_rotateAngle = 360*m_persent/100;
    int side = qMin(width(), height());
    QRectF outRect(0, 0, side, side);//矩形长宽为窗口的长宽
    QRectF inRect(20, 20, side-40, side-40);
    QString valueStr = QString("%1%").arg(QString::number(m_persent));

    //画外圆
    p.setPen(Qt::NoPen);
    p.setBrush(QBrush(QColor(97, 117, 118)));
    p.drawEllipse(outRect);
    //画内圆
    p.setBrush(QBrush(QColor(255, 107, 107)));
    p.drawPie(outRect, (90-m_rotateAngle)*16, m_rotateAngle*16);
    //画遮罩，遮罩颜色为窗口颜色
    p.setBrush(palette().window().color());
    p.drawEllipse(inRect);
    //画文字
    QFont f = QFont("Microsoft YaHei", 15, QFont::Bold);
    p.setFont(f);
    p.setFont(f);
    p.setPen(QColor("#555555"));
    p.drawText(inRect, Qt::AlignCenter, valueStr);

本文转载自：
https://blog.youkuaiyun.com/wanghualin033/article/details/78704274