qt鼠標的小例子

1、QMouseEvent中的座標
QMouseEvent中保存了兩個座標，一個是全局座標，當然另外一個是局部座標。
全局座標（globalPos（））即是桌面屏幕座標(screen coordinates)，這個跟windows下的調用getCursorPos函數得到的結果一致。
局部座標（pos（））即是相對當前active widget的座標，左上角座標爲（0， 0）。

補充一個公式：
this->mapFromGlobal(this->cursor().pos()) = event.pos()

2、鼠標跟蹤
在qt中，鼠標跟蹤對應函數mouseMoveEvent。但是，默認情況下他並不能如期象你想象的那樣響應鼠標的移動。此時，你只需在合適的位置調用一下函數setMouseTracking(true)即可。
If mouse tracking is switched off, mouse move events only occur if a mouse button is pressed while the mouse is being moved.
If mouse tracking is switched on, mouse move events occur even if no mouse button is pressed.
默認情況下，mouseMoveEvent響應你按下鼠標的某個鍵（拖動，但不侷限於左鍵拖動）的鼠標移動。

3、鼠標左鍵拖動和左鍵點擊的判斷
鼠標左鍵點擊很容易判斷，一般就是在重寫mousePressEvent函數，示例如下：
void XXXWidget::mousePressEvent(QMouseEvent *event)
{
if(event->button() == Qt::LeftButton)
{
       // todo ...
}
}
左鍵拖動的判斷一般放在mouseMoveEvent函數中，但是你不能向上例一樣來判斷，因爲該函數的event參數總是返回Qt::NoButton。你可以這樣做：
void XXXWidget::mouseMoveEvent(QMouseEvent *event)
{
if(event->buttons() & Qt::LeftButton)
{
       // todo ...
}
}
參考教材實例，增加了註釋和新功能，方便大家交流學習
// mouseevent.cpp
#include "mouseevent.h"
MouseEvent::MouseEvent( ):


QMainWindow()
{
    setWindowTitle(tr("Get Mouse Event"));
    setCursor(Qt::CrossCursor); //設置鼠標爲十字星
    labelStatus = new QLabel();
    labelStatus->setMinimumSize(500,20);
    labelStatus->setFrameShape(QFrame::WinPanel);//設置標籤形狀
    labelStatus->setFrameShadow(QFrame::Sunken); //設置標籤陰影;
    labelStatus->setText(tr("Mouse Position:"));
    labelStatus -> setFixedWidth (100);
    labelMousePos = new QLabel();
    labelMousePos->setText(tr(""));
    labelMousePos -> setFixedWidth (100);
    statusBar()->addPermanentWidget(labelStatus);//給狀態欄添加永久的部件
    statusBar()->addPermanentWidget(labelMousePos);
    this->setMouseTracking ( true);//自動跟蹤鼠標（默認情況下，mouseMoveEvent響應你按下鼠標的某個鍵的鼠標移動。）
  }
  
MouseEvent::~MouseEvent(){


}


void MouseEvent::mouseMoveEvent ( QMouseEvent * e )//鼠標移動事件響應
{    
    //1.獲取局部鼠標位置
     labelMousePos ->setText("("+QString::number(e->x())+","+QString::number(e->y())+")");
    //2.獲取全局鼠標位置
    QPoint coursePoint;
    coursePoint = QCursor::pos();//獲取當前光標的位置
    labelMousePos ->setText("("+QString::number(coursePoint.x())+","+QString::number(coursePoint.y())+")");
}


void MouseEvent::mousePressEvent ( QMouseEvent * e )//鼠標單擊事件響應
{
   QString str="("+QString::number(e->x())+","+QString::number(e->y())+")";
   if(e->button()==Qt::LeftButton){
      statusBar()->showMessage (tr("Mouse Left Button Pressed:")+str);//顯示臨時信息
   }
   else if(e->button()==Qt::RightButton){
                statusBar()->showMessage (tr("Mouse Right Button Pressed:")+str);
           }
          else if(e->button()==Qt::MidButton){
                       statusBar()->showMessage (tr("Mouse Middle Button Pressed:")+str);
         }
   }


void MouseEvent::mouseDoubleClickEvent( QMouseEvent * e )//鼠標雙擊事件響應
{       QString str="("+QString::number(e->x())+","+QString::number(e->y())+")";
         if(e->button()==Qt::LeftButton){
               statusBar()->showMessage (tr("Mouse Left Button Double Clicked:")+str);
          }
         else if(e->button()==Qt::RightButton){
                       statusBar()->showMessage (tr("Mouse Right Button Double Clicked:")+str);
                }
               else if(e->button()==Qt::MidButton){
                             statusBar()->showMessage (tr("Mouse Middle Button Double Clicked:")+str);
                      }
}


void MouseEvent::mouseReleaseEvent ( QMouseEvent * e )//鼠標鬆開事件響應
{
        QString str="("+QString::number(e->x())+","+QString::number(e->y())+")";
         statusBar()->showMessage (tr("Mouser Released:")+str,3000);
}


-------------//  mouseevent.h
#ifndef MOUSEEVENT_H
#define MOUSEEVENT_H


#include <QtGui>
class MouseEvent : public QMainWindow
{                    Q_OBJECT
            public:MouseEvent();
           ~MouseEvent();
private:
      QLabel *labelStatus;
      QLabel *labelMousePos;
      protected :
          void mouseMoveEvent ( QMouseEvent * e );
          void mousePressEvent ( QMouseEvent * e );
          void mouseReleaseEvent ( QMouseEvent * e );
          void mouseDoubleClickEvent( QMouseEvent * e );
};


#endif


//main.cpp


#include
<QtGui/QApplication>
#include "mouseevent.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MouseEvent w;w.show();
    return app.exec();
}