Qt自定义控件12：简易仪表盘

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:"<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;idrawLine(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();}