小编给大家分享一下如何使用Qt自定义控件实现多彩色仪表盘，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

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具体内容如下

Qt自定义控件4：多彩色仪表盘

思路：外围三色的圆弧 红：蓝：绿 = 1：2：1，总共占270度。刻度线是根据所在圆弧的颜色而画，刻度线的角度也是根据坐标系的旋转而画。刻度值是根据刻度线的角度得到所要画的刻度的左上角的坐标，然后构成一个矩形，根据矩形画出刻度值。指针是根据四个点的坐标直接画的四边形，再旋转坐标系实现指针旋转的效果。下方的文字直接得到坐标横纵坐标位置得到矩形画出value的值

关键代码：CMPassrate3.cpp

void CMPassrate3::paintEvent(QPaintEvent *event){  int width = this->width();  int height = this->height();  int side = qMin(width, height);  QPainter painter(this);  painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);  painter.translate(width / 2, height / 2);  painter.scale(side / 200.0, side / 200.0);  drawBG(&painter);  drawE(&painter);  drawLine(&painter);  drawText(&painter);  drawBootomText(&painter);  drawPoint(&painter);}void CMPassrate3::drawE(QPainter* painter){  painter->setPen(Qt::NoPen);  QRect rectOut(-outRadius,-outRadius,2*outRadius,2*outRadius);  QRect rectInn(-innRadius,-innRadius,2*innRadius,2*innRadius);  painter->save();  painter->setBrush(QColor("#04EEB2"));  QPainterPath path;  path.arcTo(rectOut,-45,270.0/4);  QPainterPath subPath;  subPath.addEllipse(rectInn);  path -= subPath;  painter->drawPath(path);  painter->restore();  painter->save();  QPainterPath bluePath;  QPainterPath blueSubPath;  painter->setBrush(QColor("#2DC5F6"));  bluePath.arcTo(rectOut,-45+(270.0/4),270.0/2);  blueSubPath.addEllipse(rectInn);  bluePath -= blueSubPath;  painter->drawPath(bluePath);  painter->restore();  painter->save();  QPainterPath redPath;  QPainterPath redSubPath;  painter->setBrush(QColor("#FA468C"));  redPath.arcTo(rectOut,-45+270.0*3/4,270.0/4);  redSubPath.addEllipse(rectInn);  redPath -= redSubPath;  painter->drawPath(redPath);  painter->restore();}void CMPassrate3::drawLine(QPainter* painter){  painter->save();  painter->rotate(135);  //270/8度一格  for(int i = 0;i<9;i++){    if(i<3){      painter->setPen(QColor("#FA468C"));    }else if(i<6){      painter->setPen(QColor("#2DC5F6"));    }else{      painter->setPen(QColor("#04EEB2"));    }    QLine line(QPoint(lineStart,0),QPoint(innRadius,0));    painter->drawLine(line);    painter->rotate(270.0/8);  }  painter->restore();}void CMPassrate3::drawPoint(QPainter* painter){  const QPoint point[4]{    QPoint(0,0),QPoint(0,6),QPoint((lineStart-3)*qCos(135*3.14/180),(lineStart-3)*qSin(135*3.14/180)),QPoint(-6,0)  };  float range = 270.0/100*value;  painter->save();  painter->setBrush(QColor("#C2E481"));  painter->rotate(range);  painter->drawConvexPolygon(point,4);  painter->restore();}void CMPassrate3::drawBG(QPainter* painter){//可以自行添加背景图片实现更加精美的效果//  painter->save();//  QImage image(":/image/images/bg1.jpg");//  QRect rect(-this->width(),-this->height(),this->width()*2,this->height()*2);//  painter->drawImage(rect,image);//  painter->restore();}void CMPassrate3::drawText(QPainter *painter){  painter->save();  //初始为  painter->setPen(Qt::black);  QFont font = painter->font();  font.setPixelSize(8);  painter->setFont(font);  float x,y;  for(float i =0;i<=100;i+=12.5){    x = lineStart*qCos((135+(270.0/8)*((i+1)/12.5))*3.14/180);    y = lineStart*qSin((135+(270.0/8)*((i+1)/12.5))*3.14/180);    QRect rect;    if(i<50){      rect.setX(x);      rect.setY(y);    }else if(i>50){      rect.setX(x-17);      rect.setY(y-7);    }else{      rect.setX(x);      rect.setY(y);    }    rect.setWidth(17);    rect.setHeight(10);    painter->drawText(rect,Qt::AlignCenter,QString::number(i));  }  painter->restore();}void CMPassrate3::drawBootomText(QPainter *painter){  painter->save();  painter->setPen(Qt::black);  QFont font = painter->font();  font.setPixelSize(25);  painter->setFont(font);  painter->translate(0,outRadius-12);  int length = 20;  QRect rect(-length,-length,length*2,length*2);  painter->drawText(rect,Qt::AlignCenter,QString::number(value));  painter->restore();}

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