Cocos2d-x Scene Update
Update
You can override update method in your scene(cocos2d::Layer).
GameScene.h
class GameScene : public cocos2d::Layer { public: void update(float dt); }
GameScene.cpp
void GameScene::update(float dt) { Size visibleSize = Director::getInstance()->getVisibleSize(); Vec2 origin = Director::getInstance()->getVisibleOrigin(); // Update position etc... }
Background scroll
This example is longitudinal scroll.
bool GameScene::init() { ////////////////////////////// // 1. super init first if ( !Layer::init() ) { return false; } Size visibleSize = Director::getInstance()->getVisibleSize(); Vec2 origin = Director::getInstance()->getVisibleOrigin(); // Create background(create 2 images, easy version) for (int i=0; i < 2; i++) { backgroundSpriteArray[i] = Sprite::create("space.png"); backgroundSpriteArray[i]->setPosition(Point(visibleSize.width / 2, (-1 * visibleSize.height * i) + visibleSize.height / 2)); this->addChild(backgroundSpriteArray[i], -1); } } void GameScene::update(float dt) { Size visibleSize = Director::getInstance()->getVisibleSize(); Vec2 origin = Director::getInstance()->getVisibleOrigin(); // Update background(height scroll) for (int i=0; i < 2; i++) { if (backgroundSpriteArray[i]->getPosition().y >= visibleSize.height + (visibleSize.height /2) - 1) { backgroundSpriteArray[i]->setPosition(Point( (visibleSize.width / 2) + origin.x, (-1 * visibleSize.height) + (visibleSize.height / 2))); } } for (int i=0; i < 2; i++) { backgroundSpriteArray[i]->setPosition(Point(backgroundSpriteArray[i]->getPosition().x, backgroundSpriteArray[i]->getPosition().y + (0.75 * visibleSize.height * dt))); } }
Position update and enemy emerge
We can separate position update and emerge feature.
Add additional schedule method in init and implement enemy manager.
We have items in header std::vector
bool GameScene::init() { // General Update this->scheduleUpdate(); // Update enemy this->schedule(schedule_selector(GameScreen::enemy), 1.0); // 1.0 is interval return true; }
General update
for (int i=0; i < items.size(); i++) { items[i]->setPosition(Point(items[i]->getPosition().x, items[i]->getPosition().y + (0.75 * visibleSize.height * dt))); // If the asteroid is out of display, delete if ( items[i]->getPosition().y > visibleSize.height * 2) { this->removeChild(items[i]); items.erase(items.begin() + i); } }
Emerge
void GameScene::emerge(float dt) { Size visibleSize = Director::getInstance()->getVisibleSize(); Vec2 origin = Director::getInstance()->getVisibleOrigin(); int index = (arc4random() % 3) + 1; Sprite *tempE = Sprite::create("enemy.png"); int xRandomPosition = (arc4random() % (int)(visibleSize.width - (tempE->getContentSize().width / 2))) + (tempE->getContentSize().width / 2); tempE->setPosition(Point(xRandomPosition + origin.x, -tempE->getContentSize().height + origin.y)); items.push_back(tempE); this->addChild(items[items.size()-1], -1); }