zh.md

第四章——如何发射子弹

现在我们让英雄角色发射一些子弹消灭敌人，添加以下代码，使能层级的触摸功能，如下所示。

// cpp with cocos2d-x
this->setTouchEnabled(true); or this->setIsTouchEnabled(true);

现在便可以接受到触摸事件了。

在“HelloWorldScene.h”文件中声明回调函数“void ccTouchesEnded(cocos2d::CCSet* touches, cocos2d::CCEvent* event);”，然后在“HelloWorldScene.cpp”文件中执行该函数。

// cpp with cocos2d-x
void HelloWorld::ccTouchesEnded(CCSet* touches, CCEvent* event)
{
    // Choose one of the touches to work with
    CCTouch* touch = (CCTouch*)( touches->anyObject() );
    CCPoint location = touch->locationInView();
    location = CCDirector::sharedDirector()->convertToGL(location);

    // Set up initial location of projectile
    CCSize winSize = CCDirector::sharedDirector()->getWinSize();
    CCSprite *projectile = CCSprite::create("Projectile.png", 
        CCRectMake(0, 0, 20, 20));
    projectile->setPosition( ccp(20, winSize.height/2) );

    // Determinie offset of location to projectile
    int offX = location.x - projectile->getPosition().x;
    int offY = location.y - projectile->getPosition().y;

    // Bail out if we are shooting down or backwards
    if (offX <= 0) return;

    // Ok to add now - we've double checked position
    this->addChild(projectile);

    // Determine where we wish to shoot the projectile to
    int realX = winSize.width
                         + (projectile->getContentSize().width/2);
    float ratio = (float)offY / (float)offX;
    int realY = (realX * ratio) + projectile->getPosition().y;
    CCPoint realDest = ccp(realX, realY);

    // Determine the length of how far we're shooting
    int offRealX = realX - projectile->getPosition().x;
    int offRealY = realY - projectile->getPosition().y;
    float length = sqrtf((offRealX * offRealX) 
                                        + (offRealY*offRealY));
    float velocity = 480/1; // 480pixels/1sec
    float realMoveDuration = length/velocity;

    // Move projectile to actual endpoint
    projectile->runAction( CCSequence::create(
        CCMoveTo::create(realMoveDuration, realDest),
        CCCallFuncN::create(this, 

        callfuncN_selector(HelloWorld::spriteMoveFinished)), 
        NULL) );
}

现在即可编译并运行，触摸显示屏（或者在模拟器上用鼠标点显示屏）便会出现子弹效果。 顺便说一句：为了保持代码与Object-C代码相同，从“float”到“int”之间会出现一些警告对话框，这个不用担心。

Win32平台界面

iPhone界面

Android界面