void GamePlayingLayer::setViewPointCenter(CCPoint position){
CCSize winSize = CCDirector::sharedDirector()->getWinSize();
float x = MAX(position.x,winSize.width/2);
float y = MAX(position.y,winSize.height/2);
float mapWidthInPixel = _tileMap->getMapSize().width*_tileMap->getTileSize().width;
float mapHeightInPixel = _tileMap->getMapSize().height*_tileMap->getTileSize().height;
x = MIN(x,mapWidthInPixel/CCDirector::sharedDirector()->getContentScaleFactor()-winSize.width/2);
y = MIN(y,mapHeightInPixel/CCDirector::sharedDirector()->getContentScaleFactor()-winSize.height/2);
CCPoint actualPosition = ccp(x,y);
CCPoint centerOfView = ccp(winSize.width/2,winSize.height/2);
CCPoint viewPoint = ccpSub(centerOfView, actualPosition);
this->setPosition(viewPoint);
}