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：

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

Cocos2d-x里面如何实现MVC(五)

猜你喜欢