这篇文章主要介绍了Qt自定义控件如何实现多彩色仪表盘，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。

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Qt自定义控件4：多彩色仪表盘

先看效果图：

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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