Cocos2d-x 3.2 - Chapter 3 - How to Move a sprite

Cocos2d-x 3.2 - Chapter 3 - How to Move a sprite

Cocos2d-x 3.2 - Step by Step Cocos2dxSimpleGame Series

在上一篇 Cocos2d-x 3.2 - Chapter 2 - How to Add a sprite 中，我們已經增加了一位英雄。但是英雄只有一個人太孤單了，所以我們來增加一些敵人。

addTarget() 這個函式會讓敵人隨機的出現，並從右向左移動。

void HelloWorld::addTarget()
{
 Sprite *target = Sprite::create("Target.png", Rect(0, 0, 27, 40));

 // Determine where to spawn the target along the Y axis
 Size winSize = Director::getInstance()->getWinSize();
 int minY = target->getContentSize().height / 2;
 int maxY = winSize.height - target->getContentSize().height / 2;
 int rangeY = maxY - minY;
 // srand( TimGetTicks() );
 int actualY = (rand() % rangeY) + minY;

 // Create the target slightly off-screen along the right edge,
 // and along a random position along the Y axis as calculated
 target->setPosition(Point(winSize.width + (target->getContentSize().width / 2), actualY));
 this->addChild(target);

 // Determine speed of the target
 int minDuration = (int)2.0;
 int maxDuration = (int)4.0;
 int rangeDuration = maxDuration - minDuration;
 // srand( TimGetTicks() );
 int actualDuration = (rand() % rangeDuration) + minDuration;

 // Create the actions
 FiniteTimeAction* actionMove =
  MoveTo::create((float)actualDuration,
  Point(0 - target->getContentSize().width / 2, actualY));

 FiniteTimeAction* actionMoveDone =
  CallFuncN::create(std::bind(&HelloWorld::spriteMoveFinished, this, std::placeholders::_1));

 target->runAction(Sequence::create(actionMove, actionMoveDone, NULL));
}

其中 CallFuncN::create(std::bind(&HelloWorld::spriteMoveFinished, this, std::placeholders::_1)) 使用了回呼函式，所以我們需要宣告 spriteMoveFinished 函式在 HelloWorld。

void HelloWorld::spriteMoveFinished(Node* sender)
{
 Sprite *sprite = (Sprite *)sender;
 this->removeChild(sprite, true);
}

接著，我們需要定時讓敵人出現在場景上，加入下列這段程式到 init 函中的 return 之前

this->schedule(schedule_selector(HelloWorld::gameLogic), 1.0);

然後實作 gameLogic() 函式

void HelloWorld::gameLogic(float dt)
{
 this->addTarget();
}

好了，所有的工作都完成了，建置然後看看結果吧：

參考資料：
Cocos2d-x
http://www.cocos2d-x.org/

Step by Step Cocos2dxSimpleGame Series (Old Version for cocos2d-x v2.x)
http://www.cocos2d-x.org/wiki/Step_by_Step_Cocos2dxSimpleGame_Series