思路：画一个占270度的圆弧，然后定义一个定时器，定时旋转坐标系，实现旋转的效果。圆弧需要使用渐变色，实现颜色越来越浅的效果

关键代码：CMProcessBar1.cpp

CMProcessBar1::CMProcessBar1(QWidget *parent) :  QWidget(parent),  ui(new Ui::CMProcessBar1){  ui->setupUi(this);  QTimer *timer = new QTimer;  connect(timer,QTimer::timeout,this,updaterRotation);// 定时旋转坐标系  timer->start(3);//定时3毫秒}CMProcessBar1::~CMProcessBar1(){  delete ui;}void CMProcessBar1::updaterRotation(){ //循环360度旋转坐标系  rotation++;  if(rotation == 360){    rotation = 0;  }  update();}void CMProcessBar1::paintEvent(QPaintEvent *event){//根据QPaintPath画出渐变色的圆弧  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);  QConicalGradient gra(QPoint(0,0),0);  gra.setColorAt(0,QColor("#3BB6FE"));  gra.setColorAt(1,QColor("#FFFFFF"));  QBrush brush(gra);  int radis = 40;  int sider = 5;  QRect rect(-radis,-radis,radis*2,radis*2);  QPainterPath path;  path.arcTo(rect,0, 270);  QPainterPath subPath;  subPath.addEllipse(rect.adjusted(sider, sider, -sider, -sider));  path = path-subPath;  painter.setBrush(brush);//QColor("#66CFFF")  painter.setPen(Qt::NoPen);  painter.rotate(rotation);  painter.drawPath(path);}