1、widget.h文件
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>//注意我使用的是Qt5,Qt4与Qt5的区别可以参考http://qt-project.org/wiki/Transition_from_Qt_4.x_to_Qt5
#include<QMouseEvent>
namespace Ui {
class Widget;
}
class Widget : public QWidget
{
    Q_OBJECT
    
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
    QPoint move_point; //移动的距离
    bool mouse_press; //鼠标按下
    //鼠标按下事件
    void mousePressEvent(QMouseEvent *event);
   //鼠标释放事件
    void mouseReleaseEvent(QMouseEvent *event);
   //鼠标移动事件
    void mouseMoveEvent(QMouseEvent *event);
    
private:
    Ui::Widget *ui;
};
#endif // WIDGET_H2、widget.cpp文件
#include "widget.h"
#include "ui_widget.h"
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    this->setMouseTracking(false);
     setWindowFlags(Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint);//设置主窗口无边框
}
Widget::~Widget()
{
    delete ui;
}
void Widget::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton)
     {
        this->setMouseTracking(true);
          mouse_press = true;
          //鼠标相对于窗体的位置(或者使用event->globalPos() - this->pos())
          move_point = event->pos();;
     }
}
void Widget::mouseReleaseEvent(QMouseEvent *event)
{
    //设置鼠标为未被按下
        mouse_press = false;
}
void Widget::mouseMoveEvent(QMouseEvent *event)
{
    //若鼠标左键被按下
  //  qDebug()<<"mouse_press="<<event->globalPos();
        if(mouse_press)
        {
            //鼠标相对于屏幕的位置
            QPoint move_pos = event->globalPos();
           //移动主窗体位置
           this->move(move_pos - move_point);
        }
}
原文地址:http://blog.csdn.net/tengweitw/article/details/38817595