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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();}
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