Cocos2d-x里面如何实现MVC(五)

本文基于前面两篇文章，如果您还没有看过，建议先阅读下面两篇文章：

· cocos2d-x里面如何实现mvc（三）

· cocos2d-x里面如何实现mvc（四）

更新Model

    当用户从工具箱中选一个小工具，然后把它放置到game board上面去时，我们需要编码响应这些事件。在上一篇文章中，我们已经实现了GameBoardViewDelegate的touchedAtRow方法。我们还需要给这个协议再添加一个接口方法。如下所示：

class GameBoardViewDelegate
{
public:
virtual void touchAtGrid(GameBoard *gameBoard, int row, int column) = 0;
virtual void touchWithToolBoxItemAtIndex(GameBoard *gameBoard, int index) = 0;
};    我们需要修改touch事件处理器，这样就可以判断我们到底是触摸了工具箱还是game board。

void GameBoardView::ccTouchesBegan(CCSet *pTouches, CCEvent *pEvent)
{
CCTouch *touch = (CCTouch*) pTouches->anyObject();
if(touch == NULL)
return;

// 置换坐标，等效如下
//CCPoint location = touch->locationInView(touch->view());
//location = CCDirector::sharedDirector()->convertToGL(location);
CCPoint point = this->convertTouchToNodeSpace(touch);

// 下面假设游戏区与工具区8:2来划分宽度
CCSize size = CCDirector::sharedDirector()->getWinSize();
CCRect *gameBoardRectangle = new CCRect(0, 0, size.width*0.8, size.height);
CCRect *toolBoxRectangle = new CCRect(size.width*0.8, 0, size.width*0.2, size.height);

if(CCRect::CCRectContainsPoint(*gameBoardRectangle, point)){
// calculate row and column touched by the user and call a delegate method
int row = 0;
int column = 0;
// ...
this->gameBoardViewDelegate->touchAtGrid(gameBoard, row, column);
} else if (CCRect::CCRectContainsPoint(*toolBoxRectangle, point)){
int index = 0;
// calculate toolbox item index based on a touch coordinate
this->gameBoardViewDelegate->touchWithToolBoxItemAtIndex(gameBoard, index);
}
}

    在controller类里面处理touch事件是非常简单的，我们只需要持有一个model的引用，然后基于touch事件来调用model的方法就行了。我们的接口看起来和下面差不多，只是省略掉了一些实现细节：

class GameBoard : public CCObject
{
public:
// ...
GamePiece* getGamePieceFromToolBoxItemAtIndex(int index);
public:
// ...
int selectedToolBoxItemIndex;
};    然后，我们在GameBoardController里面完全实现GameBoardViewDelegate的两个方法。

void GameBoardController::touchAtGrid(GameBoard *gameBoard, int row, int column)
{
// if the toolbox item is selected move item from toolbox to game board
if(gameBoard->selectedToolBoxItemIndex != -1){
GamePiece *gamePiece = gameBoard->getGamePieceFromToolBoxItemAtIndex(gameBoard->selectedToolBoxItemIndex);
gameBoard->putGamePiece(gamePiece, row, column);
}
}

void GameBoardController::touchWithToolBoxItemAtIndex(GameBoard *gameBoard, int index) {
// keep the toolbox selection state in the Model
gameBoard->selectedToolboxItemIndex = index;
}

    到目前为止，我们实现了，用户可以点击工具箱中的小工具，然后把它们放置到game board中的一个小方块上面，同时model类在中间起了桥梁作用。

通知view关于model的改变

    为了在view里面反映出model的状态更改，我们可以在model有变化的时候给view发送通知消息，然后view就可以根据不同的消息来作出不同的响应了。和我们在实现view通过controller一样，这里我们也定义了一个GameBoardDelegate，用来通知view model的变化。

class GameBoardDelegate
{
public:
virtual void didPutGamePiece(GamePiece *gamePiece, int row, int column) = 0;
};

class GameBoard : public CCObject
{
// ...
public:
void setGameBoardDelegate(GameBoardDelegate *aGameBoardDelegate);
private:
GameBoardDelegate *gameBoardDelegate;
};

void GameBoard::putGamePiece(GamePiece *gamePiece, int row, int column)
{
// ...
// store game piece
// notify that the game piece was put on a gameboard
this->gameBoardDelegate->didPutGamePiece(gamePiece, row, column);
}

void GameBoard::setGameBoardDelegate(GameBoardDelegate *aGameBoardDelegate)
{
this->gameBoardDelegate = aGameBoardDelegate;
}

    在GameBoardView里面实现GameBoardDelegate的时候，当我们需要在game board上面放置一个小工具的时候，我们定义了一个CCSprite。

class GameBoardView :
public CCLayer, public GameBoardDelegate
{
// ...
};

void GameBoardView::initWithGameBoard(GameBoard *aGameBoard, GameBoardViewDelegate *aDelegate)
{
// ...
this->gameBoard = aGameBoard;
this->gameBoard->retain();
this->gameBoard->setGameBoardDelegate(this);
this->gameBoardViewDelegate = aDelegate;
// ...
}

void GameBoardView::didPutGamePiece(GamePiece *gamePiece, int row, int column)
{
// create CCSprite and put it on a game board at corresponding position
CCSprite *gamePieceSprite = CCSprite::spriteWithFile("CloseNormal.png");
// ...
this->addChild(gamePieceSprite, 1);
}

总结

    现在框架中所有的部分都联系起来了，model、view和controller三者组成了著名的MVC模式

· View接收touch事件，然后把事件传递给controller,

· Controller 响应用户的touch事件，然后更新model

· model 更新它自身的状态, 处理游戏逻辑，然后告诉view它改变了哪些东西。

· View则基于Model当前的状态来更新自己的显示