详解Qt自定义控件实现进度仪表盘教程_F11 - 专业站长和开发者的学习网站

思路：外围的线共100根（自定义，可改变），总共占270度，然后按照先画一条线然后旋转坐标系的思路画出完整的线。内部即是一个灰色的背景圆，一个圆弧和中间的value对应的文字。

关键代码：CMPassrate2.cpp

void CMPassrate2::paintEvent(QPaintEvent *event){//界面绘制事件
 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);
 
 drawBGE(&painter); //画背景圆
 drawTextE(&painter);//画文字所在圆弧
 drawText(&painter);//画文字
 drawLines(&painter);//画最外部的线
}
 
void CMPassrate2::updateValue(float value){//提供给外部的方法，用于更新value
 this->value = value;
 update();//每次更新value后，都重绘界面
}
void CMPassrate2::drawLines(QPainter* painter){
 painter->save();
 QPen pen;
 pen.setColor(QColor("#A7DD42"));
 pen.setWidth(2);
 painter->setPen(pen);
 
 float range = 270.0/lineCount; //自定义所有的线加起来占270度，100条线
 painter->rotate(135);//旋转135度，开始画线，总共画270度。
 QLine line(QPoint(outLineRadius,0),QPoint(innLineRadius,0));
 for(int i = 1;i<=lineCount;i++){
  if(i>value){
   QPen pen;
   pen.setColor(QColor("#D7D7D7"));
   pen.setWidth(2);
   painter->setPen(pen);
  }
  painter->drawLine(line);
  painter->rotate(range);
 }
 painter->restore();
}
void CMPassrate2::drawBGE(QPainter* painter){
 painter->save();
 painter->setPen(Qt::NoPen);
 painter->setBrush(QColor("#EAEAEA"));
 QRect rect(-bgERadius,-bgERadius,bgERadius*2,bgERadius*2);
 painter->drawEllipse(rect);
 painter->restore();
}
void CMPassrate2::drawTextE(QPainter* painter){
 painter->save();
 painter->setPen(Qt::NoPen);
 painter->setBrush(QColor("#2DC877"));
 
 QPainterPath path;
 QRect rectOut(-textOutRadius,-textOutRadius,textOutRadius*2,textOutRadius*2);
 path.arcTo(rectOut,0,360);
 
 QPainterPath subPath;
 QRect rectInn(-textInnRadius,-textInnRadius,textInnRadius*2,textInnRadius*2);
 subPath.addEllipse(rectInn);
 path -= subPath;
 painter->drawPath(path);
 painter->restore();
}
void CMPassrate2::drawText(QPainter* painter){
 painter->save();
 painter->setPen(QColor("#62A0DB"));
 QRect rectInn(-textInnRadius,-textInnRadius,textInnRadius*2,textInnRadius*2);
 QFont font = painter->font();
 font.setPixelSize(textSize);
 painter->setFont(font);
 painter->drawText(rectInn,Qt::AlignCenter,QString::number(value));
 painter->restore();
}