本文实例为大家分享了Qt自定义控件实现简易仪表盘的具体代码，供大家参考，具体内容如下

Qt自定义控件12：简易仪表盘（根据liudianwu大神的界面自己写的代码，建议去学习刘大神，会受益良多的）

先看效果图：

思路：画270度的圆弧，圆弧根据占比分为两种颜色，根据占比在圆弧上画出一个圆球作为标志，然后就是刻度线和刻度值。刻度线是根据坐标系旋转画出，刻度值是根据角度求出x,y坐标值构造出一个矩形画出刻度值（不要用坐标系旋转画刻度值，那样刻度值的角度也会旋转，写出的字不是正的，效果不好）。最后就是在中心画value。

关键代码：

void CMPassrate5::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);

  drawE(&painter);
  drawEPoint(&painter);
  drawLine(&painter);
  drawEText(&painter);
  drawValue(&painter);
}

void CMPassrate5::drawE(QPainter* painter){
  QRect rect(-radius,-radius,2*radius,2*radius);
  painter->save();
  painter->setPen(Qt::NoPen);

  QPainterPath path;
  QPainterPath subPath;
  QPainterPath outPath;
  QPainterPath outPubPath;
  outPath.arcTo(rect,-45,outRange);
  outPubPath.addEllipse(rect.adjusted(side,side,-side,-side));
  outPath -= outPubPath;
  color.setAlpha(100);
  painter->setBrush(color);
  painter->drawPath(outPath);


  path.arcTo(rect,-45+outRange,range);
  subPath.addEllipse(rect.adjusted(4,4,-4,-4));
  path -= subPath;
  color.setAlpha(180);
  painter->setBrush(color);
  painter->drawPath(path);

  painter->restore();
}

void CMPassrate5::drawEPoint(QPainter* painter){
  //圆球位置就在outRange尽头处
  painter->save();
  color.setAlpha(180);
  painter->setPen(Qt::NoPen);
  painter->setBrush(color);

  float x = (radius-side/2)*qCos((range+135)*3.14/180);
  float y = (radius-side/2)*qSin((range+135)*3.14/180);
  qDebug()<<"x:"<<x<<" y:"<<y;
  painter->drawEllipse(QPoint(x,y),side,side);
  painter->restore();
}

void CMPassrate5::drawLine(QPainter* painter){
  painter->save();
  painter->rotate(135);
  color.setAlpha(100);
  painter->setPen(color);
  QLine line(QPoint(radius-side-lineLength,0),QPoint(radius-side,0));

  for(int i = 0;i<lineCount;i++){
    painter->drawLine(line);
    painter->rotate(270.0/lineCount);
  }
  painter->restore();
}

void CMPassrate5::drawEText(QPainter* painter){
  painter->save();
//  painter->rotate(135);
  painter->setPen(Qt::black);
  float textRange = 270.0/(textCount-1);
  float x,y;
  for(int i = 0;i<=10;i++){
    x = (radius-side-lineLength)*qCos((textRange*i+135)*3.14/180);
    y = (radius-side-lineLength)*qSin((textRange*i+135)*3.14/180);
    if(i<5){
      QRect rect(x,y-4,20,10);
      painter->drawText(rect,Qt::AlignCenter,QString::number(i*10));
    }else if(i ==5){
      QRect rect(x-7,y,20,10);
      painter->drawText(rect,Qt::AlignCenter,QString::number(i*10));
    }else{
      QRect rect(x-20,y-5,20,10);
      painter->drawText(rect,Qt::AlignCenter,QString::number(i*10));
    }

  }
  painter->restore();
}

void CMPassrate5::drawValue(QPainter* painter){
  painter->save();
  QPen pen = painter->pen();
  pen.setColor(color);
  pen.setWidth(2);
  painter->setPen(pen);
  QFont font = painter->font();
  font.setPixelSize(45);
  painter->setFont(font);

  QRect rect(-25,-25,50,50);
  painter->drawText(rect,Qt::AlignCenter,QString::number(value));
  painter->restore();
}