Qt鼠标滚轮、左键按下并移动事件

继承 class QWidget 类，重写鼠标响应事件虚函数：

    virtual void wheelEvent(QWheelEvent * event);
    virtual void mousePressEvent(QMouseEvent * event);
    virtual void mouseMoveEvent(QMouseEvent * event);

重写鼠标滚轮响应事件：

void ViewWidge::wheelEvent(QWheelEvent * event)
{

	double zoomFactor = 1;
	if(event->delta() > 0)      
		zoomFactor = 1 / 0.8;
	else
		zoomFactor = 0.8;
	
    //zoom in or zoom out 操作 zoomFactor 

	update();   //窗口更新 void ViewWidget::paintEvent(QPaintEvent *event)
}

 鼠标左键按下事件：

void ViewWidget::mousePressEvent(QMouseEvent * event)
{
    switch (event->button()) {
    case Qt::LeftButton:
        {
              //鼠标左键按下处理
        }
        break;
    case Qt::RightButton:     // 0x00000002
        {
             //鼠标右键按下处理
        }
        break;
    default:
        break;
    }
}

鼠标左键按下并且移动鼠标事件响应：

void ViewWidgetEx::mouseMoveEvent(QMouseEvent *event)
{
	QPoint currentMousePt = event->pos();
	Qt::MouseButtons btns = event->buttons();
	if (Qt::LeftButton == (btns & Qt::LeftButton) )
	{
		//左键按下鼠标移动响应事件
		update();      //更新窗口
	}
}