第三步：移动sprite小精灵

打开第二步的项目，给游戏添加敌人enemies

自定义addTarget()函数来完成这项工作

使敌人从屏幕左边出生，以一个随机random的速度向左移动

在HelloWorldScene.h头文件加入void addTarget()声明

在HelloWorldScene.cpp文件中实现该函数

并添加using namespace cocos2d引入cocos2d命名空间

1// cpp with cocos2d-x
 2void HelloWorld::addTarget()
 3{
 4    CCSprite *target = CCSprite::create("Target.png", 
 5        CCRectMake(0,0,27,40) );
 6
 7    // 设置敌人出生的Y轴坐标
 8    CCSize winSize = CCDirector::sharedDirector()->getWinSize();
 9    int minY = target->getContentSize().height/2;
10    int maxY = winSize.height
11                          -  target->getContentSize().height/2;
12    int rangeY = maxY - minY;
13    // srand( TimGetTicks() );
14    int actualY = ( rand() % rangeY ) + minY;
15
16    // Create the target slightly off-screen along the right edge,
17    // and along a random position along the Y axis as calculated
18    target->setPosition( 
19        ccp(winSize.width + (target->getContentSize().width/2), 
20        actualY) );
21    this->addChild(target);
22
23    // 设置随机速度
24    int minDuration = (int)2.0;
25    int maxDuration = (int)4.0;
26    int rangeDuration = maxDuration - minDuration;
27    // srand( TimGetTicks() );
28    int actualDuration = ( rand() % rangeDuration )
29                                        + minDuration;
30
31    // 创建移动动作，并设置动作的回调函数
32    CCFiniteTimeAction* actionMove = 
33        CCMoveTo::create( (float)actualDuration, 
34        ccp(0 - target->getContentSize().width/2, actualY) );
35    CCFiniteTimeAction* actionMoveDone = 
36        CCCallFuncN::create( this, 
37        callfuncN_selector(HelloWorld::spriteMoveFinished));
38    target->runAction( CCSequence::create(actionMove, 
39        actionMoveDone, NULL) );
40}

声明和定义HelloWorld::spriteMoveFinished(CCNode* sender)函数

// cpp with cocos2d-x
2void HelloWorld::spriteMoveFinished(CCNode* sender)
3{
4  CCSprite *sprite = (CCSprite *)sender;
5  this->removeChild(sprite, true);
6}

即当敌人从右边移动到左边之后，将结束该敌人的生命，不再显示

现在，敌人已经设计好了，接下来的工作就是把它创建出来

这里将敌人以每秒一个的速率创建出来

在HelloWord::init()中添加

1// cpp with cocos2d-x
2// Call game logic about every second
3this->schedule( schedule_selector(HelloWorld::gameLogic), 1.0 );

并声明定义HelloWorld::gameLogic(float dt)函数

1// cpp with cocos2d-x
2void HelloWorld::gameLogic(float dt)
3{
4    this->addTarget();
5}

编译运行一下看看，是不是敌人从右边出生，移动到左边之后就消失？