最近想在widget界面上绘制区域，需要对widget类进行提升，从而对paintEvent事件进行重写，实现绘制效果。
（1）通过Qt designer拖拽出一个widget；

（1）右击此widget，选择“提升为”；

（3）填写类名，点击添加，提升。此时widget类会被提升为newWidget（自定义类名）；

（4）在项目里添加对应的newwidget.h和newwidget.cpp文件，并对paintEvent事件进行重写，便会实现绘制效果

附上主要代码
newwidget.h

#ifndef NEWWIDGET_H
#define NEWWIDGET_H#include <QWidget>
#include <QPen>
#include <QPainter>
#include <QMouseEvent>
#include <QPoint>
#include <math.h>
class newWidget : public QWidget
{Q_OBJECTpublic:newWidget(QWidget *parent = 0);~newWidget();QMatrix m_Matrix;protected:void paintEvent(QPaintEvent* event);void mousePressEvent(QMouseEvent* event);void mouseMoveEvent(QMouseEvent* event);	private:QPen m_drawPen;QPoint m_Point;std::vector<QPoint> temp;std::vector<std::vector<QPoint>> pathvec;QPainter* painter;
};#endif // NEWWIDGET_H

newwidget.cpp

#include "newWidget.h"newWidget::newWidget(QWidget *parent): QWidget(parent)
{m_drawPen=QPen(Qt::yellow,20);		//设置画笔属性m_drawPen.setStyle(Qt::SolidLine);this->setMouseTracking(true);
}newWidget::~newWidget()
{if(painter != NULL){delete painter;painter = NULL;}
}void newWidget::mouseMoveEvent(QMouseEvent* event)
{setCursor(Qt::CrossCursor);	
}void newWidget::mousePressEvent(QMouseEvent* event)
{setCursor(Qt::ArrowCursor);	if(event->button() == Qt::LeftButton)	//按下鼠标左键{m_Point = event->pos();temp.push_back(m_Point);			//把当前点位push进路径容器中pathvec.push_back(temp);newWidget::update();				//触发绘制事件}else if(event->button() == Qt::RightButton){painter->end();						//绘制结束pathvec.push_back(temp);temp.clear();						//路径容器清空，为下一次绘制做准备newWidget::update();}else if(event->button() == Qt::MiddleButton){pathvec.clear();					//按下鼠标中键，路径容器全部清空，删除绘制图像newWidget::update();}
}void newWidget::paintEvent(QPaintEvent* event)
{painter = new QPainter(this);painter->setPen(m_drawPen);m_drawPen.setWidth(2);painter->setRenderHint(QPainter::Antialiasing);painter->setRenderHint(QPainter::TextAntialiasing);QPainterPath RoiPath;int j = 0;for(j=0;j<pathvec.size();j++){for(int i=0;i<pathvec[j].size();i++){if(i==0){RoiPath.moveTo(m_Matrix.map(pathvec[j][i]));RoiPath.addEllipse(m_Matrix.map(pathvec[j][i]),2,2);}else{RoiPath.lineTo(m_Matrix.map(pathvec[j][i]));RoiPath.moveTo(m_Matrix.map(pathvec[j][i]));RoiPath.addEllipse(m_Matrix.map(pathvec[j][i]),2,2);}	      }}eRoiPath.closeSubpath();painter->drawPath(RoiPath);
}