Qt繪製雷達圖（效果圖）

• 效果圖如下：

• 原理：

自定義控件，並使用QPainter等繪製。
雷達圖主要包括的元素有： 同心圓、十字架、文本標籤、不同顏色、不同樣式的圓圈、餘暉等；可以設置目標顯示的方位、距離等，經過我的測試，顯示100個目標，界面不會卡頓，滿足正常環境下的使用。

• paintEvent（）的主要代碼：

void SkyplotWidget::paintEvent(QPaintEvent *)
{
    QSize          widgetSize(this->size());
    QPalette       p = palette();
    QPainter      *painter = new QPainter(this);
    float          topMargin ;
    float          leftMargin;
    float          size;
    float          satelliteSize;
    float          fontSize;
    float          availableWidth    = widgetSize.width ();
    float          availableHeight   = widgetSize.height();

    if( availableHeight > availableWidth )
    {
        size = widgetSize.width() * p_marginScale;
        topMargin   = ( widgetSize.width() - widgetSize.width() * p_marginScale + widgetSize.height() - widgetSize.width() ) / 2.0;
        leftMargin  = ( widgetSize.width() - widgetSize.width() * p_marginScale ) / 2.0;
    }
    else
    {
        size = widgetSize.height() * p_marginScale;
        leftMargin = ( widgetSize.height() - widgetSize.height() * p_marginScale + widgetSize.width() - widgetSize.height()) / 2.0;
        topMargin  = ( widgetSize.height() - widgetSize.height() * p_marginScale ) / 2.0;
    }

    satelliteSize = size * p_satScale;
    painter->setRenderHint(QPainter::Antialiasing, p_antialiased);
    painter->translate( leftMargin, topMargin );  //重新設置座標原點
    fontSize = size * p_fontScale;
    painter->setFont(QFont( "Arial", static_cast< int >(fontSize)));

    //圓圈
    for(int i=0; i <= p_ellipses; i++)
    {
        float radius = size / 2.0 - i * ( size / ( 2.0  * p_ellipses ));
        painter->setPen( QPen( p_gridColor, p_gridWidth ) );
        painter->drawEllipse(QPoint( size/2.0, size/2.0 ), static_cast< int >( radius ), static_cast< int >(radius));
        if(p_withGridLabels)
        {
            painter->setPen( QPen( p_gridTextColor, p_gridWidth -2.5 ) );
            double tmp = ((p_ellipses - i) * (mMonitorScope / p_ellipses));
            QString distance = QString::number(((p_ellipses - i) * (mMonitorScope / p_ellipses)) ,10 , 2);
            painter->drawText(QPoint(size/2.0 + p_textMargin, size/2.0 - (radius + p_textMargin)), QString("%1 km").arg(distance)); //距離刻度
        }
    }

    //十字架
    for(int i=0; i < p_crosses; i++)
    {
        QLineF line1,line2;
        float angle = (static_cast<float>(i) * 90.0) / (static_cast<float>(p_crosses));
        line1.setP1( QPoint( size/2.0, size/2.0 ) );
        line1.setLength( size/2.0 );

        QRectF textRect(0, 0, 4.0 * fontSize, fontSize + 2.0);

        for(int c = 0; c < 4; c++)
        {
            line1.setAngle(angle + c*90.0 + 90.0);
            painter->setPen(QPen(p_gridColor, p_gridWidth));
            painter->drawLine(line1);
            if( p_withGridLabels )
            {
                painter->setPen(QPen( p_gridTextColor, p_gridWidth));
                line2 = QLineF(line1);
                line2.setLength(size/2.0 + 2.0 * fontSize);
                textRect.moveCenter(line2.p2());
                if(i > 0)
                    painter->drawText( textRect, Qt::AlignCenter, QString("%1").arg((int)(360 - (c*90 ) - angle) , 3 , 10 , QChar('0')));
                else
                {
                    if(c == 0)
                    {
                        painter->drawText( textRect, Qt::AlignCenter,QString("000"));
                    }
                    else if(c == 1)
                    {
                        painter->drawText( textRect, Qt::AlignCenter, QString("270"));
                    }
                    else if(c == 2)
                    {
                        painter->drawText( textRect, Qt::AlignCenter, QString("180"));
                    }
                    else if(c == 3)
                    {
                        painter->drawText( textRect, Qt::AlignCenter, QString("090"));
                    }
                }
            }
        }
    }

    QBrush innerBrush = QBrush( Qt::SolidPattern );
    QBrush outerBrush = QBrush( );
    //衛星
    foreach( auto s, satellites )
    {
        //------w---設置每一個衛星的大小
        satelliteSize = size * s.rsize;
        // skip invisible satellites
        if(     s.state & SatelliteState::Invisible       ||  // the invisible flag is set

                ( !( s.state & SatelliteState::Visible ) &         // neither visible nor half-visible
                  !( s.state & SatelliteState::HalfVisible ) ) ||

                (  s.state & SatelliteState::Flashing && flash )    // flashing flag is set and flash is active
                )
            continue;

        QRectF labelRect( 0, 0, s.label.length() * satelliteSize, satelliteSize+2 );

        double nmdX = 0,nmdY = 0;  //衛星的X軸座標,衛星的Y軸座標
        calculatePos(s.az , s.distance ,nmdX, nmdY);
        QPoint satPos(size/2.0 + size*(nmdX/mMonitorScope) * 0.5,size/2.0 +  size*(nmdY/mMonitorScope) * 0.5);

        // define the color's alpha value (0.3 or 1.0)
        QColor innerColor = s.innerColor;
        QColor outerColor = s.outerColor;
        QColor fontColor  = s.fontColor;
        if( s.state & SatelliteState::Visible )
        {
            innerColor.setAlphaF( 1.0 );
            outerColor.setAlphaF( 1.0 );
            fontColor.setAlphaF( 1.0 );
        }
        else
        {
            innerColor.setAlphaF( 0.3 );
            outerColor.setAlphaF( 0.3 );
            fontColor.setAlphaF( 0.3 );
        }

        // paint the inner circle
        innerBrush.setColor( innerColor );
        painter->setBrush( innerBrush );
        if( s.state & SatelliteState::Marked )
            painter->setPen( QPen( outerColor, satelliteSize/4 ) );
        else
            painter->setPen( QPen( p_gridColor, 0 ) );
        painter->drawEllipse( satPos, static_cast< int >( satelliteSize ), static_cast< int >( satelliteSize ) );


        // write the text
        painter->setPen( QPen( fontColor, 2 ) );
        painter->setFont( QFont( "Arial", static_cast< int >( satelliteSize ),  QFont::Bold ) );
        labelRect.moveCenter( satPos );
        painter->drawText( labelRect, Qt::AlignCenter, s.label );

    }

    foreach (auto l, indicatrix)
    {
        if(  l.lineState & SatelliteState::Invisible       ||  // the invisible flag is set
             ( !( l.lineState & SatelliteState::Visible ) &         // neither visible nor half-visible
               !( l.lineState & SatelliteState::HalfVisible ) ) ||
             (  l.lineState & SatelliteState::Flashing && flash )    // flashing flag is set and flash is active
             )
            continue;

        QPoint spoint ( l.point1.rx() * size / 100 + size/2, l.point1.ry() * size/100 + size/2);
        QPoint epoint ( l.point2.rx() * size / 100 + size/2, l.point2.ry() * size/100 + size/2);

        painter->setPen(QPen(l.lineColor,1.5,Qt::DashDotLine,Qt::RoundCap));
        painter->drawLine(spoint,epoint);
    }

    //餘暉掃描
    //   int len = m_drawArea.width();
    qreal x = size/2.0 + (qreal)size/2 * cos(-m_pieRotate*3.14159/180);
    qreal y = size/2.0 + (qreal)size/2 * sin(-m_pieRotate*3.14159/180);
    painter->setPen(QPen(Qt::green));
    painter->drawLine(QPoint( size/2.0, size/2.0 ),QPointF(x,y));

    //扇形
    QConicalGradient gradient;
    gradient.setCenter(QPoint( size/2.0, size/2.0 ));
    gradient.setAngle(m_pieRotate + 180); //漸變與旋轉方向恰好相反，以扇形相反的邊作爲漸變角度。
    gradient.setColorAt(0.4,QColor(169,253,51,100)); //從漸變角度開始0.5 - 0.75爲扇形區域，由於Int類型計算不精確，將範圍擴大到0.4-0.8
    gradient.setColorAt(0.8,QColor(169,253,51,0));
    painter->setBrush(QBrush(gradient));
    painter->setPen(Qt::NoPen);
    painter->drawPie(0,0,size,size,m_pieRotate*16,90*16);
    //--------------------------------------------------
    delete painter;
}在這裏插入代碼片

• 下載地址：

代碼下載地址稍後貼在下方評論區。