1.运行截图

2.源码

.h
#ifndef _QROUNDPROGRESSBAR_H_
#define _QROUNDPROGRESSBAR_H_
#include <QWidget>
class QRoundProgressBar : public QWidget
{
    Q_OBJECT
    //进度条形状
    enum BarStyle
    {
        //圆环状
        StyleDonut = 0,
        //圆饼状
        StylePie,
        //圆线状
        StyleLine
    };
public:
    QRoundProgressBar(QWidget *parent , BarStyle style = StyleLine);
    ~QRoundProgressBar();
public:
    //设置扫描弧度起始角度
    void setStartAngle(double position);
    //设置轮廓画笔的宽度
    void setOutlinePenWidth(double penWidth);
    //设置画笔宽度
    void setDataPenWidth(double penWidth);
    //设置进度条精度 88.88%,几位小数
    void setDecimals(int count);
    //设置进度条风格
    void setBarStyle(BarStyle style);
    //设置范围
    void setRange(double min, double max);
    //设置当前值
    void setValue(int val);
    //设置当前值
    void setValue(double val);
    //设置最小值
    void setMinimum(double min);
    //设置最大值
    void setMaximum(double max);
protected:
    void paintEvent(QPaintEvent *event);
    //画基础图形
    void drawBase(QPainter& p, const QRectF& baseRect, const QRectF &innerRect);
    //根据值画出进度条
    void drawValue(QPainter& p, const QRectF& baseRect, double value, double arcLength, const QRectF & innerRect
        , double innerDiameter);
    //画中心文字
    void drawText(QPainter& p, const QRectF& innerRect, double value);
private:
    double   m_min;                                 //最小值
    double   m_max;                                 //最大值
    double   m_value;                               //当前值
    BarStyle m_barStyle;                            //进度条风格
    int      m_decimals;                            //进度条精度
    double   m_startAngel;                          //扫描弧度起始角度
    double   m_outlinePenWidth;                     //轮廓画笔的宽度
    double   m_dataPenWidth;                        //画笔宽度
};
#endif // _QROUNDPROGRESSBAR_H_
.cpp
#include "QRoundProgressBar.h"
#include <QPainter>
#include <QPointF>
#include <QtMath>
QRoundProgressBar::QRoundProgressBar(QWidget *parent , BarStyle style)
    : QWidget(parent)
    , m_min(0)
    , m_max(100)
    , m_value(0)
    , m_startAngel(90)
    , m_barStyle(style)
    , m_outlinePenWidth(0)
    , m_dataPenWidth(0)
    , m_decimals(0)
{
}
QRoundProgressBar::~QRoundProgressBar()
{
}
void QRoundProgressBar::setStartAngle(double angle)
{
    if (angle != m_startAngel)
    {
        m_startAngel = angle;
        update();
    }
}
void QRoundProgressBar::setOutlinePenWidth(double penWidth)
{
    if (penWidth != m_outlinePenWidth)
    {
        m_outlinePenWidth = penWidth;
        update();
    }
}
void QRoundProgressBar::setDataPenWidth(double penWidth)
{
    if (penWidth != m_dataPenWidth)
    {
        m_dataPenWidth = penWidth;
        update();
    }
}
void QRoundProgressBar::setDecimals(int count)
{
    if (count >= 0 && count != m_decimals)
    {
        m_decimals = count;
        update();
    }
}
void QRoundProgressBar::setBarStyle(BarStyle style)
{
    if (style != m_barStyle)
    {
        m_barStyle = style;
        update();
    }
}
void QRoundProgressBar::setRange(double min, double max)
{
    m_min = min;
    m_max = max;
    if (m_max < m_min)
    {
        qSwap(m_max, m_min);
    }
    if (m_value < m_min)
    {
        m_value = m_min;
    }
    else if (m_value > m_max)
    {
        m_value = m_max;
    }
    update();
}
void QRoundProgressBar::setValue(double val)
{
    if (m_value != val)
    {
        if (val < m_min)
        {
            m_value = m_min;
        }
        else if (val > m_max)
        {
            m_value = m_max;
        }
        else
        {
            m_value = val;
        }
        update();
    }
}
void QRoundProgressBar::setValue(int val)
{
    setValue(double(val));
}
void QRoundProgressBar::setMinimum(double min)
{
    setRange(min, m_max);
}
void QRoundProgressBar::setMaximum(double max)
{
    setRange(m_min, max);
}
void QRoundProgressBar::paintEvent(QPaintEvent* /*event*/)
{
    //外圈直径
    double outerDiameter = this->width();
    //外圈矩形
    QRectF baseRect(0, 0, outerDiameter, outerDiameter);
    QPainter p(this);
    p.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
    //画背景矩形填充白色
    p.fillRect(baseRect, QBrush(QColor("#FFFFFF")));
    //内圆直径
    double innerDiameter;
    //内圈矩形
    QRectF innerRect;
    //计算内圈矩形
    if (m_barStyle == StyleLine)
    {
        innerDiameter = outerDiameter - m_outlinePenWidth;
    }
    else if(m_barStyle == StyleDonut)
    {
        innerDiameter = outerDiameter * 0.9;
    }
    double delta = (outerDiameter - innerDiameter) / 2;
    innerRect = QRectF(delta, delta, innerDiameter, innerDiameter);
    //画基础图形
    drawBase(p, baseRect, innerRect);
    //计算当前步长比例
    double arcStep = 360.0 / (m_max - m_min) * m_value;
    //根据值画出进度条
    drawValue(p, baseRect, m_value, arcStep, innerRect, innerDiameter);
    //画文字
    drawText(p, baseRect, m_value);
    p.end();
}
void QRoundProgressBar::drawBase(QPainter &p, const QRectF &baseRect, const QRectF &innerRect)
{
    switch (m_barStyle)
    {
        case StyleDonut:
        {
            QPainterPath dataPath;
            dataPath.setFillRule(Qt::OddEvenFill);
            dataPath.moveTo(baseRect.center());
            dataPath.addEllipse(innerRect);
            QPen pen;
            pen.setColor(QColor("#DEE3E7"));
            pen.setWidth(10);
            p.setPen(pen);
            p.setBrush(QBrush(QColor("#FFFFFF")));
            p.drawPath(dataPath);
            break;
        }
        case StylePie:
        {
            p.setPen(QPen(QColor("#FFFFFF"), m_outlinePenWidth));
            p.setBrush(QBrush(QColor("#DEE3E7")));
            p.drawEllipse(baseRect);
            break;
        }
        case StyleLine:
        {
            p.setPen(QPen(QColor("#FFFFFF"), m_outlinePenWidth));
            p.setBrush(Qt::NoBrush);
            p.drawEllipse(baseRect.adjusted(m_outlinePenWidth / 2, m_outlinePenWidth / 2, -m_outlinePenWidth / 2, -m_outlinePenWidth / 2));
            break;
        }
        default:
        {
            break;
        }
    }
}
void QRoundProgressBar::drawValue(QPainter &p, const QRectF &baseRect , double value, double arcLength
                          , const QRectF & innerRect, double innerDiameter)
{
    if (value == m_min)
    {
        return;
    }
    if (m_barStyle == StyleLine)
    {
        p.setPen(QColor("#2F8DED"));
        p.setBrush(Qt::NoBrush);
        p.drawArc(baseRect,m_startAngel * 16, -arcLength * 16);
    }
    else if (m_barStyle == StyleDonut)
    {
        QPen pen;
        pen.setColor(QColor("#2F8DED"));
        pen.setWidth(10);
        pen.setCapStyle(Qt::RoundCap);
        p.setPen(pen);
        p.drawArc(innerRect, m_startAngel*16 , -16*arcLength);
    }
    else
    {
        //获取中心点坐标
        QPointF centerPoint = baseRect.center();
        QPainterPath dataPath;
        dataPath.setFillRule(Qt::WindingFill);
        dataPath.moveTo(centerPoint);
        //逆时针画弧长
        dataPath.arcTo(baseRect, m_startAngel, -arcLength);
        if (m_barStyle == StylePie)
        {
            dataPath.lineTo(centerPoint);
            p.setPen(QPen(QColor("#2F8DED"), m_dataPenWidth));
        }
        p.setBrush(QBrush(QColor("#2F8DED")));
        p.drawPath(dataPath);
    }
}
void QRoundProgressBar::drawText(QPainter &p, const QRectF &rect, double value)
{
    QString textToDraw = "%";
    double percent = (value - m_min) / (m_max - m_min) * 100.0;
    textToDraw = QString::number(percent, 'f', m_decimals) + textToDraw;
    QFont f;
    f.setFamily("微软雅黑");
    f.setPixelSize(20);
    p.setFont(f);
    p.setPen(QColor("#606266"));
    p.drawText(rect, Qt::AlignCenter, textToDraw);
}