QMouseEvent下可以被重写的虚函数:
1.void mousePressEvent(QMouseEvent *event); //鼠标键被按下的事件.
2.void mouseReleaseEvent(QMouseEvent *event); //鼠标键被放开的事件.
3.void mouseMoveEvent(QMouseEvent *event); //按住鼠标键移动的事件.
4.void mouseDoubleClickEvent(QMouseEvent *event); //鼠标键被双击的事件.

QMouseEvent类中的重要函数:
1.QPoint pos(); //返回鼠标相对于父部件的坐标.
2.QPoint globalPos(); //返回鼠标的全局坐标.
3.QMouseButton button(); //返回鼠标被点击的键.

“c.cpp”下的代码:

#include"c.h"c::c(QWidget*parent):QMainWindow(parent){ui.setupUi(this);}c::~c(){}voidc::mouseMoveEvent(QMouseEvent*event){//保存鼠标移动的时候的尾坐标.end=event->pos();//用来重绘更新.可以理解为调用paintEvent函数，但不一定是立即调用的.在此程序中可以理解为:马上更新窗口上显示的图像.update();}voidc::paintEvent(QPaintEvent*event){//画一个矩形.QPainterpainter(this);painter.setPen(Qt::red);QRecttemp(start,end);painter.setBrush(Qt::green);painter.drawRect(temp);}voidc::mouseReleaseEvent(QMouseEvent*event){//当左键释放后，保存尾坐标.if(event->button()==Qt::LeftButton){this->end=event->pos();update();}}voidc::mousePressEvent(QMouseEvent*event){//当左键被按下时，保存首坐标.并更新重绘.if(event->button()==Qt::LeftButton){//点击的时候定下初始位置.this->start=event->pos();}}123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051

“c.h”的代码:

#ifndefC_H#defineC_H#include<QtWidgets/QMainWindow>#include"ui_c.h"#include<QPixmap>#include<QMouseEvent>#include<QMessageBox>#include<QPainter>#include<QPaintEvent>#include<QVector>classc:publicQMainWindow{Q_OBJECTpublic:c(QWidget*parent=0);~c();protected:voidmouseMoveEvent(QMouseEvent*event);voidmouseReleaseEvent(QMouseEvent*event);voidmousePressEvent(QMouseEvent*event);voidpaintEvent(QPaintEvent*event);private:Ui::cClassui;QPointstart;QPointend;};#endif//C_H1234567891011121314151617181920212223242526272829303132

最后是”main.cpp”下的代码:

#include"c.h"#include<QtWidgets/QApplication>intmain(intargc,char*argv[]){QApplicationa(argc,argv);cw;w.show();returna.exec();}