QT绘画仪表盘

代码一步一步讲，就不写用啥之类的了，暗部走来，自己找使用的类以及使用方法

1、创建工程

2、重载paintEvent

#include <QMainWindow>
#include <QPainter>
#include <QPaintEvent>

protected:
    virtual void paintEvent(QPaintEvent *event);

void MainWindow::paintEvent(QPaintEvent *event)
{

}

3、构建绘画对象，调整表盘位置、画笔位置、刷子之类的

    //创建对象
    QPainter m_painter(this);
    //表盘宽度不变，高度-100，中心位置在前面两个小的的中间
    int m_width = this->width();
    int m_height = this->height() - 100;
    int radius = ((m_width > m_height)?m_height:m_width)/2.0;
    //移动画笔到中下方位置
    m_painter.translate(m_width/2,m_height*0.6);
    //启用反锯齿
    m_painter.setRenderHint(QPainter::Antialiasing, true);
    m_painter.setPen(Qt::NoPen);
    //设置画刷颜色
    m_painter.setBrush(QColor(138,43,226));

4、画刻度线

//刻度线
    DrawSmallScale(m_painter, radius - 60);

private:
    void DrawSmallScale(QPainter & painter, int radius);

void MainWindow::DrawSmallScale(QPainter & painter, int radius)
{
    //组装点路径图（刻度）
    QPainterPath pointPath_small;
    pointPath_small.moveTo(-2, -2);
    pointPath_small.lineTo(2, -2);
    pointPath_small.lineTo(2, 8);
    pointPath_small.lineTo(-2, 8);

    QPainterPath pointPath_big;
    pointPath_big.moveTo(-2, -2);
    pointPath_big.lineTo(2, -2);
    pointPath_big.lineTo(2, 20);
    pointPath_big.lineTo(-2, 20);

    //绘制61个小点
    for(int i = 0; i < 121; i += 2)
    {
        QPointF point(0, 0);
        painter.save();
        point.setX(radius* qCos(((210-i*2)*M_PI)/180));
        point.setY(radius* qSin(((-210+i*2)*M_PI)/180));
        painter.translate(point.x(), point.y());
        painter.rotate(-120+i*2);

        if(i<80)
        {
            painter.setBrush(QColor(0, 0, 0));
        }
        if(i>=80)
        {
            painter.setBrush(QColor(235, 70, 70));
        }
        if(i%5 == 0)
        {
            painter.drawPath(pointPath_big);//绘画大刻度
        }
        else
        {
            painter.drawPath(pointPath_small);//绘画小刻度
        }
        painter.restore();
    }
}

5、刻度数字

    //刻度数字
    DrawDigital(m_painter, radius - 90);

void DrawDigital(QPainter & painter, int radius);

void MainWindow::DrawDigital(QPainter &painter, int radius)
{
    //设置画笔，画笔默认NOPEN
    painter.setPen(QColor(0, 0, 0));
    QFont font;
    font.setFamily("Arical");
    font.setPointSize(15);
    font.setBold(true);
    painter.setFont(font);
    for(int i=0;i<13;++i)
    {
        QPointF point(0, 0);
        painter.save();
        point.setX(radius* qCos(((210-i*20)*M_PI)/180));
        point.setY(radius* qSin(((210-i*20)*M_PI)/180));
        painter.translate(point.x(), -point.y());
        painter.rotate(-120+i*20);
        painter.drawText(-25, 0, 50, 20, Qt::AlignCenter, QString::number(i*20));
        painter.restore();
    }
    //还原画笔
    painter.setPen(Qt::NoPen);
}

6、逐渐发光外扇形

/*所有形状绘画*/
    //逐渐发光外扇形
    DrawCircle(m_painter, radius - 35);

void DrawCircle(QPainter & painter, int radius);

void MainWindow::DrawCircle(QPainter &painter, int radius)
{
    //保存绘图对象
    painter.save();
    //计算大小圆路径
    QPainterPath outRing;
    QPainterPath inRing;
    outRing.moveTo(0,0);
    inRing.moveTo(0,0);
    outRing.arcTo(-radius, -radius, 2*radius, 2*radius, -30, 240);
    inRing.addEllipse(-radius+50, -radius+50, 2*(radius-50), 2*(radius-50));
    outRing.closeSubpath();
    //设置渐变色
    QRadialGradient radialGradient(0,0,radius,0,0);
    radialGradient.setColorAt(1, QColor(0,82,199));
    radialGradient.setColorAt(0.92, Qt::transparent);
    //设置画刷
    painter.setBrush(radialGradient);
    //大圆减小圆
    painter.drawPath(outRing.