Qt仪表自绘
本片文章介绍仪表控件是如何绘制的，首先上图：
绘制原理：
根据上图介绍绘制的原理，继承QWidget类，重写绘制事件函数：
protected:
void paintEvent(QPaintEvent *);
在绘制事件中绘制仪表。
仪表绘制分为五个部分：绘制外弧线、绘制刻度颜色块，绘制圆心、绘制指针、绘制显示文本。
绘制外弧线：
首先先绘制一个外饼形圆、然后再绘制一个内饼形圆，内外圆颜色不同，这样就会形成一个外弧线：
绘制刻度色块：
使用弧线绘制一块一块的弧度色块，色块间隔空白的地方也是弧线色块只是背景色是透明色：
绘制圆心：
在最下方水平中心的地方绘制一个圆：
绘制指针：
以圆心为起点，要指向的位置为终点绘制一条指针直线
绘制显示文本:
在圆心的下方绘制指针指向的值
以上就是仪表绘制的步骤。 仪表控件类封装：
#ifndef DASHBOARD_H #define DASHBOARD_H #include <QWidget> #include <QPainter> #include <QDebug> #include <qmath.h> class Dashboard : public QWidget { Q_OBJECT public: explicit Dashboard(QWidget *parent = nullptr); void setValue(double value); void setTextFromat(QString value); void setTextFont(QFont font); double getValue(); QString getTextFromat(); QFont getTextFont(); signals: public slots: protected: void paintEvent(QPaintEvent *); void drawCircular(QPainter *painter);//绘制圆弧 void drawScale(QPainter *painter);//绘制刻度 void drawCenterCircle(QPainter *painter);//绘制中心圆 void drawPointerIndicator(QPainter *painter);//绘制指针 void drawValue(QPainter *painter);//绘制Text private: double minValue; //最小值 double maxValue; //最大值 double value; //目标值 int precision; //精确度,小数点后几位 int startAngle; //开始旋转角度 int endAngle; //结束旋转角度 QColor outerCircleColor; //外圆背景颜色 QColor innerCircleColor; //内圆背景颜色 QColor pieColor1; //饼圆颜色1 QColor pieColor2; //饼圆颜色2 QColor pieColor3; //饼圆颜色3 QColor pieColor4; //饼圆颜色4 QColor pieColor5; //饼圆颜色5 QColor pieColor6; //饼圆颜色6 QColor pieColor7; //饼圆颜色7 QColor coverCircleColor; //覆盖圆背景颜色 QColor scaleColor; //刻度尺颜色 QColor pointerColor; //指针颜色 QColor centerCircleColor; //中心圆颜色 QColor textColor; //文字颜色 double currentValue; //当前值 QString textFromat;//文本格式 QFont textFont;//文本字体 }; #endif // DASHBOARD_H #include “dashboard.h” Dashboard::Dashboard(QWidget *parent) : QWidget(parent) { outerCircleColor = QColor(80,80,80); //外圆背景颜色 innerCircleColor = QColor(60,60,60); //内圆背景颜色 pieColor1 = QColor(0,128,64); //饼圆颜色1 pieColor2 = QColor(0,64,0); //饼圆颜色2 pieColor3 = QColor(0,0,255); //饼圆颜色3 pieColor4 = QColor(255,128,0); //饼圆颜色4 pieColor5 = QColor(128,0,255); //饼圆颜色5 pieColor6 = QColor(128,0,0); //饼圆颜色6 pieColor7 = QColor(255,0,0); //饼圆颜色7 coverCircleColor = QColor(255,0,0); //覆盖圆背景颜色 scaleColor = QColor(252,252,252); //刻度尺颜色 pointerColor = QColor(65,234,0); //指针颜色 centerCircleColor = QColor(65,234,0); //中心圆颜色 textColor = QColor(0, 0, 0); //文本颜色 minValue = 0; //最小值 maxValue = 100; //最大值 value = 0; //目标值 startAngle = 90; //开始旋转角度 endAngle = 270; //结束旋转角度 currentValue = 77.6; //当前值 textFromat = “%1”; textFont.setPixelSize(18); } void Dashboard::setValue(double value) { currentValue = value; //当前值 } void Dashboard::setTextFromat(QString value) { textFromat = value; } void Dashboard::setTextFont(QFont font) { textFont = font; } double Dashboard::getValue() { return currentValue; } QString Dashboard::getTextFromat() { return textFromat; } QFont Dashboard::getTextFont() { return textFont; } void Dashboard::paintEvent(QPaintEvent *) { int width = this->width(); int height = this->height(); int side = qMin(width, height); //绘制准备工作,启用反锯齿,平移坐标轴中心,等比例缩放 QPainter painter(this); painter.save(); painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing); painter.translate(width / 2, height – height / 3);//平移坐标轴 将中心点作为原点（0，0） painter.scale(side / 200.0, side / 200.0);//缩放坐标轴系统 drawCircular(&painter);//外弧线 drawScale(&painter);//刻度标 drawCenterCircle(&painter);//绘制中心圆 drawPointerIndicator(&painter);//绘制指针 drawValue(&painter);//绘制文本 painter.restore(); } void Dashboard::drawCircular(QPainter *painter) { int radius = 100/*100*/; QRectF rect(-radius, -radius, radius * 2, radius * 2); painter->save(); painter->setPen(Qt::NoPen); //绘制开始饼圆 painter->setBrush(outerCircleColor); painter->drawPie(rect,-3 * 16, 186 * 16); radius = 95/*95*/; rect = QRectF(-radius, -radius, radius * 2, radius * 2); painter->setPen(QPen(QBrush(QColor(255,255,255)),1,Qt::SolidLine)/*Qt::NoPen*/); painter->setBrush(QColor(255,255,0/*255*/)); painter->drawPie(rect,-3 * 16, 186 * 16); painter->restore(); } void Dashboard::drawScale(QPainter *painter) { int radius = 85; QRectF rect(-radius, -radius, radius * 2, radius * 2); painter->save(); painter->setPen(Qt::NoPen); int start = -1; for(int i = 0;i < 21;i ++) { if(i/3 < 1) { painter->setPen(QPen(pieColor7,6,Qt::SolidLine)); painter->setBrush(pieColor7); }else if (i/3 < 2) { painter->setPen(QPen(pieColor6,6,Qt::SolidLine)); painter->setBrush(pieColor6); }else if (i/3 < 3){ painter->setPen(QPen(pieColor5,6,Qt::SolidLine)); painter->setBrush(pieColor5); }else if (i/3 < 4){ painter->setPen(QPen(pieColor4,6,Qt::SolidLine)); painter->setBrush(pieColor4); }else if (i/3 < 5){ painter->setPen(QPen(pieColor3,6,Qt::SolidLine)); painter->setBrush(pieColor3); }else if (i/3 < 6){ painter->setPen(QPen(pieColor2,6,Qt::SolidLine)); painter->setBrush(pieColor2); }else { painter->setPen(QPen(pieColor1,6,Qt::SolidLine)); painter->setBrush(pieColor1); } painter->drawArc(rect,start*16, 2*16); start = start + 6; painter->setPen(QPen(QColor(255, 255, 255,0),6,Qt::SolidLine)); painter->setBrush(QColor(255, 255, 255,0)); painter->drawArc(rect,start*16, 3*16); start = start + 3; } painter->restore(); } void Dashboard::drawCenterCircle(QPainter *painter) { int radius = 8; painter->save(); painter->setPen(Qt::NoPen); painter->setBrush(centerCircleColor); painter->drawEllipse(-radius, -radius, radius * 2, radius * 2); painter->restore(); } void Dashboard::drawPointerIndicator(QPainter *painter) { int radius = 75; painter->save(); painter->setOpacity(1.0); painter->setPen(QPen(pointerColor,4)); painter->setBrush(pointerColor); QPolygon pts; pts.setPoints(4, -5, 0, 5, 0, -5, radius,5,radius); painter->rotate(startAngle); double degRotate = (360.0 – qAbs(startAngle – endAngle)) / (maxValue – minValue) * (currentValue – minValue); painter->rotate(degRotate); painter->drawLine(0,0,0,75); painter->restore(); } void Dashboard::drawValue(QPainter *painter) { painter->save(); painter->setPen(textColor); painter->setFont(textFont); qDebug() << this->width(); QRect textRect(-200, 10, 400, 400); QString strValue = textFromat.arg(static_cast<double>(currentValue)); painter->drawText(textRect, Qt::AlignTop | Qt::AlignHCenter, strValue); painter->restore(); }<
