osgGA::KeySwitchMatrixManipulator按鍵選擇切換操作器使用

 osg::ref_ptr<osgGA::KeySwitchMatrixManipulator> keyswitchManipulator = new osgGA::KeySwitchMatrixManipulator; 
 keyswitchManipulator->addMatrixManipulator( '1', "Trackball", new osgGA::TrackballManipulator() ); 
 keyswitchManipulator->addMatrixManipulator( '2', "Flight", new osgGA::FlightManipulator() ); 
 keyswitchManipulator->addMatrixManipulator( '3', "Drive", new osgGA::DriveManipulator() ); 
 keyswitchManipulator->addMatrixManipulator( '4', "Terrain", new osgGA::TerrainManipulator() );
 viewer.setCameraManipulator( keyswitchManipulator.get() ); 

申請一個使用按鍵來切換操作器的類，即：osgGA::KeySwitchMatrixManipulator，意思是這樣的，往這個類中添操作器，添的時候帶個標識和快捷鍵，然後再把這個類添加到viewer當中，這樣viewer運行的時候就可以通過按鍵來換操作器了，真方便。

源代碼分析：osgGA\KeySwitchMatrixManipulator頭文件

 public:

        typedef std::pair<std::string, osg::ref_ptr<CameraManipulator> > NamedManipulator;
        typedef std::map<int, NamedManipulator> KeyManipMap;

        virtual const char* className() const { return "KeySwitchMatrixManipulator"; }

        /**
        Add a camera manipulator with an associated name, and a key to
        trigger the switch,
        */
        void addMatrixManipulator(int key, std::string name, CameraManipulator *cm);

    private:

        KeyManipMap _manips;

        osg::ref_ptr<CameraManipulator> _current;

用了一個map映射（C#中有Dictionary詞典），map對象是模板類，需要關鍵字key和存儲對象value兩個模板參數，map中的key和value是一個pair結構中的兩個分量：
源文件

bool KeySwitchMatrixManipulator::handle(const GUIEventAdapter& ea,GUIActionAdapter& aa)
{
    if (!_current) return false;

    bool handled = false;

    if (!ea.getHandled() && ea.getEventType()==GUIEventAdapter::KEYDOWN)
    {

        KeyManipMap::iterator it=_manips.find(ea.getKey());//找到按鍵如'E'
        if(it != _manips.end())//不爲空
        {
            CameraManipulator* selectedManipulator = it->second.second.get();//it爲一個pair，key爲pair.first value爲pair.second
            if (selectedManipulator!=_current)
            {            
                OSG_INFO<<"Switching to manipulator: "<<it->second.first<<std::endl;
                if ( !selectedManipulator->getNode() )
                {
                    selectedManipulator->setNode(_current->getNode());
                }
                selectedManipulator->setByMatrix(_current->getMatrix());//設置當前矩陣
                selectedManipulator->init(ea,aa);
                
                _current = selectedManipulator;
            }
            handled = true;
        }
    }

    return _current->handle(ea,aa) || handled;
}

添加數字切換

void KeySwitchMatrixManipulator::addNumberedMatrixManipulator(CameraManipulator *cm)
{
    if(!cm) return;
    addMatrixManipulator('1'+_manips.size(),cm->className(),cm);
}